Discovery of new 2-(3-(naphthalen-2-yl)-4,5-dihydro-1H-pyrazol-1-yl)thiazole derivatives with potential analgesic and anti-inflammatory activities: In vitro, in vivo and in silico investigations

Joining the global demand for the discovery of potent NSAIDs with minimized ulcerogenic effect, new pyrazole clubbed thiazole derivatives 5a-o were designed and synthesized. The new derivatives were initially evaluated for their analgesic activity. Eight compounds 5a, 5c, 5d, 5e, 5f, 5h, 5m, and 5o showed higher activity than Indomethacin (potency = 105-130 % vs. 100 %). Subsequently, they were picked for further evaluation of their anti-inflammatory activity, ulcerogenic liability as well as toxicological studies. Derivatives 5h and 5m showed a potential % edema inhibition after 3 h (79.39 % and 72.12 %, respectively), with a promising safety profile and low ulcer indices (3.80 and 3.20, respectively). The two compounds 5h and 5m were subjected to in vitro COX-1 and COX-2 inhibition assay. The candidate 5h showed nearly equipotent COX-1 inhibition (IC50 = 38.76 nM) compared to the non-selective reference drug Indomethacin (IC50 = 35.72 nM). Compound 5m expressed significant inhibitory activities and a higher COX-2 selectivity index (IC50 = 87.74 nM, SI = 2.05) in comparison with Indomethacin (SI = 0.52), with less selectivity than Celecoxib (SI = 8.31). Simulation docking studies were carried out to gain insights into the binding interaction of compounds 5h and 5m in the vicinity of COX-1 and COX-2 enzymes that illustrated the importance of pyrazole clubbed thiazole core in hydrogen bonding interactions. The thiazole motif of compounds 5h and 5m exhibited a well orientation toward COX-1 Arg120 key residue by hydrogen bonding interactions. Compound 5h revealed an additional arene-cation interaction with Arg120 that could rationalize its superior COX-1 inhibitory activity. Compounds 5h and 5m overlaid the co-crystallized ligand Celecoxib I differently in the active site of COX-2. Compound 5m showed an enhanced accommodation with binding energy of - 6.13 vs. - 1.70 kcal/mol of compounds 5h. The naphthalene ring of compound 5m adopted the Celecoxib I benzene sulfonamide region that is stabilized by hydrogen-arene interactions with the hydrophobic sidechains of the key residues Ser339 and Phe504. Further, the core structure of compound 5m, pyrazole clubbed thiazole, revealed deeper hydrophobic interactions with Ala513, Leu517 and Val509 residues. Finally, a sensitive and accurate UPLC-MS/MS method was developed for the simultaneous estimation of some selected promising pyrazole derivatives in rat plasma. Accordingly, compounds 5h and 5m were suggested to be promising potent analgesic and anti-inflammatory agents with improved safety profiles and a novel COX isozyme modulation activity.

Exploring the therapeutic potential of Prinsepia utilis Royle seed oil: A comprehensive study on chemical composition, physicochemical properties, anti-inflammatory, and analgesic activities

ETHNOPHARMACOLOGICAL RELEVANCE

Prinsepiautilis (PU) Royle, native to the Himalayan region, is a deciduous thorny shrub with numerous traditional uses of its roots, leaves and seeds for treatment of conditions such as rheumatic pain, joint pain, arthritis, and inflammation.

AIM OF THE STUDY

Keeping in mind the growing demand of products of natural origin as alternate medicine, the present study was undertaken to scientifically validate for the first time the traditional claims of healing pain and inflammation by evaluating the fatty oil isolated from the seeds using established in vitro and in vivo models.

MATERIALS AND METHODS

PU Seeds were Soxhlet extracted using n-hexane and fatty oil was isolated. Chemical composition of the oil was established with the aid of Gas Chromatography-Flame Ionization Detection (GC-FID) and Gas Chromatography-Mass Spectrometry (GC-MS). The oil was then subjected to in vitro anti-inflammatory activity by following the established protocols of trypsin inhibitory and bovine serum albumin denaturation assays. The acute toxicity of the oil was also studied using OECD guidelines 423. The anti-inflammatory property of the oil was further evaluated using carrageenan-induced and formalin-induced edema in the rat paw. Moreover, hot plate latency and tail immersion assay were employed to evaluate analgesic activity of the oil. To establish the quality of the oil, various physicochemical properties were also studied.

RESULTS

GC-FID and GC-MS analysis of the oil revealed the presence of linoleic acid (59.06 ± 0.00%), oleic acid (28.11 ± 0.01%), palmitic acid (9.51 ± 0.01%) and stearic acid (3.32 ± 0.01%). In vitro trypsin inhibitory and bovine serum albumin denaturation assay revealed dose-dependent notable activity of the oil with IC50 value of 63.57 μg/mL and 518.14 μg/mL, respectively. The physico-chemical characterization demonstrated that the oil possesses a low acidity and a high oxidative stability index. The oil was found to be non-toxic and displayed effective anti-inflammatory activities with significant inhibition till 4 h in carrageenan-induced and formalin-induced rat paw edema at maximum tested dose of 200 mg/kg b.w. The oil also exhibited significant results in hot plate latency and tail immersion assay with positive effects showing up to 4 h after dose administration.

CONCLUSION

These findings, besides supporting the traditional claims, suggest that P. utilis seed oil has potential therapeutic applications as a natural anti-inflammatory and analgesic agent. Further studies are warranted to explore its mechanisms of action and potential use in pharmaceutical and nutraceutical industries.

Discovery of highly functionalized grayanane diterpenoids from the flowers of Rhododendron molle as potent analgesics

A systematical investigation on the chemical constituents of the flowers of Rhododendron molle (Ericaceae) led to the isolation and characterization of thirty-eight highly functionalized grayanane diterpenoids (1-38), including twelve novel analogues molleblossomins A-L (1-12). Their structures were elucidated by comprehensive methods, including 1D and 2D NMR analysis, calculated ECD, 13C NMR calculations with DP4+ probability analysis, and single crystal X-ray diffraction. Molleblossomins A (1), B (2), and E (5) are the first representatives of 2β,3β:9β,10β-diepoxygrayanane, 2,3-epoxygrayan-9(11)-ene, and 5,9-epoxygrayan-1(10),2(3)-diene diterpenoids, respectively. Molleblossomins G (7) and H (8) represent the first examples of 1,3-dioxolane-grayanane conjugates furnished with the acetaldehyde and 4-hydroxylbenzylidene acetal moieties, respectively. All grayanane diterpenoids 1-38 were screened for their analgesic activities in the acetic acid-induced writhing model, and all of them exhibited significant analgesic activities. Diterpenoids 6, 13, 14, 17, 20, and 25 showed more potent analgesic effects than morphine at a lower dose of 0.2 mg/kg, with the inhibition rates of 51.4%, 68.2%, 94.1%, 66.9%, 97.7%, and 60.0%, respectively. More importantly, even at the lowest dose of 0.04 mg/kg, rhodomollein X (14), rhodojaponin VI (20), and rhodojaponin VII (22) still significantly reduced the number of writhes in the acetic acid-induced pain model with the percentages of 61.7%, 85.8%, and 64.6%, respectively. The structure-activity relationship was summarized and might provide some hints to design novel analgesics based on the functionalized grayanane diterpenoids.

Structurally diverse analgesic diterpenoids from the flowers of Rhododendron molle

Thirteen diterpenoids (1-13), classified into four structurally diverse carbon skeletons, including 1,5-seco-kalmane (1 and 6), grayanane (2-11), kalmane (12), and rhodomollane (13), were isolated from the flowers extract of Rhododendron molle. Among them, rhodomollinols A - E (1-5) were five new diterpenoids and their structures were elucidated by extensive spectroscopic methods including HRESIMS, UV, IR, 1D and 2D NMR, as well as quantum ECD calculations. Rhodomollinol A (1) is the first representative of a 6-deoxy-1,5-seco-kalmane diterpenoid. The abnormal NMR phenomenon of the presence of only 9 carbon resonances instead of 20 carbons in the 13C NMR spectrum of 1 was observed and elucidated by the quantum NMR calculations. All diterpenoids 1-13 showed significant analgesic activities in an acetic acid-induced writhing model. It's the first time to report the analgesic activity of a rhodomollane-type diterpenoid. At a dose of 1.0 mg/kg, diterpenoids 1-3, 6, 8, 9, and 12 reduced the writhe numbers with inhibition rates over 50%, and 9 exhibited stronger analgesic activity with a writhe inhibition rate of 89.7% than that of the positive control morphine. Importantly, even at the lowest dose of 0.04 mg/kg, rhodomollinols A (1) and B (2), rhodomollein X (7), and 2-O-methylrhodojaponin VI (9) still showed more potent analgesic effects than morphine with the writhe inhibition rates of 51.8%, 48.0%, 61.7%, and 60.0%, respectively. A preliminary structure-activity relationship might provide some clues to design potential analgesics on the basis of structurally diverse Ericaceae diterpenoids.

Discovery of (S)-flurbiprofen-based novel azine derivatives as prostaglandin endoperoxide synthase-II inhibitors: Synthesis, in-vivo analgesic, anti-inflammatory activities, and their molecular docking

The anti-inflammatory and analgesic drugs currently used are associated with several adverse effects and found to be highly unsafe for long-term use. Currently, nineteen novel bis-Schiff base derivatives (1-19) of flurbiprofen have been designed, prepared and assessed for in-vivo analgesic, anti-inflammatory and in vivo acute toxicity evaluation. The structures of the acquired compounds were deduced through modern spectroscopic techniques including HR-ESI-MS, 13C-, and 1H NMR. Amongst the series, compounds 7, 9, and 10 attributed potent activities with 93.89, 92.50, and 90.47% decreased edema, respectively compared to flurbiprofen (90.01%), however, compounds 11 and 15 exhibited significant activity of 90.00% decrease. Out of them, fourteen compounds (1-6, 8, 12-14, and 16-19) displayed good activity in the range of 68.96-86.95%. In case of an analgesic study, all the derivatives significantly (p 0.001) increased the pain threshold time particularly compound 7 had the best analgesic effect (24 ± 2.08 s) in comparison with flurbiprofen (21.66 ± 2.02 s) using hot plate test. Similarly, in the acetic acid-induced writhing test, compound 7 determined a potent inhibitory effect (60.47 %) close to flurbiprofen (59.28%). All the synthesized derivatives were found safe up to the dose of 30 mg/kg, in acute toxicity study. On a molecular scale, the synthesized compounds were modeled through a ligand-based pharmacophore study and molecular docking to have insight into the different possible interactions leading to high inhibition levels against the COX-2 enzyme.

Synthesis and in silico studies of some new pyrrolidine derivatives and their biological evaluation for analgesic and anti-inflammatory activity

BACKGROUND

An array of commercially viable intermediate molecules necessary for the synthesis of a variety of bioactive molecules are chemically synthesized by pyrrolidine and its derivatives, which play a significant role in drug design and development process.

AIM

The aim of the present research work was to explore the synthesis of some new pyrrolidine derivatives and to perform their in silico studies and finally evaluation of analgesic and anti-inflammatory activity.

OBJECTIVE

The purpose of this study was to synthesis new pyrrolidine derivatives, examine how they affected the COX-1 and COX-2 enzymes computationally, and to screen their in vivo analgesic and anti-inflammatory activity on laboratory animals.

METHOD

The new pyrrolidine derivatives were synthesized by condensing N-(3-acetylphenyl)-2-(pyrrolidin-1-yl)acetamide with substituted aniline in ethanol in the presence of catalytic amounts of glacial acetic acid. The structures of novel pyrrolidine derivatives were characterised using IR, NMR, and mass spectroscopy. Several molecular properties of the newly synthesized derivatives were calculated in order to evaluate the nature of the drug-like candidate. A specific reference cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) enzyme was used to dock the newly synthesized pyrrolidine derivatives.

RESULTS

From the observed data, it was noted that amongst all newly synthesized compounds, A-1 and A-4 exhibited the highest anti-inflammatory and analgesic effects, respectively.

CONCLUSION

On the basis of findings of present research, it was concluded that A-1 and A-4 might be utilized as a promising new lead compound for Non-Steroidal Anti-Inflammatory Drug (NSAIDs) development.

Investigation of Paracetamol Entrapped Nanoporous Silica Nanoparticles in Transdermal Drug Delivery System

An effort was made to administer paracetamol drug through transdermal patch, as no such formulation of this drug has been developed yet. The primary cause for the lack of such formulations is paracetamol's poor aqueous solubility. As a result, the current research concentrated on preparing nanomedicines, or drug-loaded nanoparticles, for delivery via transdermal formulations. Nanoparticles can improve the solubility of weakly aqueous soluble or even aqueous insoluble drugs by changing the crystalline structure of loaded medicines to an amorphous state and serving as drug permeation boosters. Silica nanoparticles (SNPs) were synthesized through sol-gel technique to achieve the aforementioned goal. DLS data revealed that the average particle size was around 100-200 nm, which was sufficient to penetrate the skin barrier. XRD analysis showed that the SNPs were amorphous, and the drug molecules lost their crystallinity after encapsulation into the nanoparticles, causing the enhancement of dissolution of drug molecules in physiological pH (pH-7.4). Different kinetic models were employed for the ex vivo dissolution data to evaluate the suitable kinetic model followed by the drug release in both burst and sustained phase. In vivo analgesic study was executed on mice applying each of the transdermal formulations to examine the performances of the patches.

Preparation and characterization of naproxen solid dispersion using different hydrophilic carriers and in-vivo evaluation of its analgesic activity in mice

Background

Solid dispersion (SD) has been used conventionally as a successful technique for improving the dissolution profile and bioavailability of poorly water-soluble drugs. The aim of this study was to progress the dissolution rate and bioavailability of naproxen (BCS class II) by SD technique.

Materials & methods

In this study, hydrophilic carriers are used for preparing solid dispersion of naproxen by evaporation method. The prepared optimized SDNs were evaluated by in-vitro drug dissolution test, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The in-vivo analgesic effects tests of the optimized SDNs (SDN-2 and SDN-5) were performed by tail immersion method and writhing method.

Results

All the prepared SDNs exhibited a significant increase in the dissolution of naproxen compared to that of the pure drug. Among them, SDN-2 (the dispersion with sodium starch glycolate at 1:2 ratio of naproxen and sodium starch glycolate) and SDN-5 (using the combination of PEG-8000 and sodium starch glycolate with naproxen at 1:1:1 ratio) showed faster dissolution rate as compared to other solid dispersions (SDNs) and pure naproxen. SDN-2 showed 5.4 times better dissolution rate and SDN-5 depicted 6.5-fold increment of dissolution rate compared to pure naproxen drug. DSC, PXRD and SEM microscopy showed that the drugs crystallinity was decreased during the preparation process. FTIR study revealed that naproxen was stable in polymeric dispersions and there was no interaction among the drug and polymers. In writhing method, the percentage inhibition of the number of writhes showed significantly greater (p < 0.01), (p < 0.0001) analgesic activity for the higher dose treatment groups SDN-2(H), and SDN-5(H), respectively, when contrasted to the pure drug naproxen. For tail immersion test, there is increase in latency time at 90 min which is significantly greater (P < 0.01), (P < 0.05), (P < 0.01) for treatment groups SDN-2(H), SDN-5(L), and SDN-5(H), respectively that ultimately authenticates that the optimized SDNs (SDN-2, SDN-5) showed better analgesic activity in mice in comparison with the pure drug.

Conclusion

It can be concluded that dissolution of the naproxen could be improved by the making solid dispersion using sodium starch glycolate and/or combination of sodium starch glycolate and PEG 8000 due to the complete transformation of drug into amorphous form with the entire loss of crystallinity, as evidenced by DSC, PXRD, and SEM and also consequences the enhanced analgesic activity in mice.

Highly oxygenated grayanane diterpenoids with structural diversity from the flowers of Rhododendron dauricum and their analgesic activities

Twenty-eight grayanane diterpenoids (1-28) including 13 new ones, named daublossomins A-M (1-13), and two new natural products, 3-O-acetylgrayanotoxin II (14) and 10-epi-grayanotoxin III (15), were isolated from the flowers of Rhododendron dauricum L. (Ericaceae). Their structures were elucidated by means of comprehensive spectroscopic methods and quantum chemical calculations (¹³C NMR-DP4+ analysis and calculated ECD), and the absolute configurations of ten grayanane diterpenoids 1, 4, 5, 7, 8, 22, 23, 25, 27, and 28 were determined by X-ray crystallographic analysis. Daublossomin A (1) represents the first example of an 11,16-epoxygrayan-6-one diterpenoid. Daublossomins B (2) and C (3) are the first examples of 9β,10β-epoxygrayanane diterpenoids, and daublossomin I (9) is the second conjugated grayan-1(5),6(7),9(10)-triene diterpenoid. Compounds 1-11 and 13-27 were evaluated for their analgesic activities in the HOAc-induced writhing test in mice, and 1-8, 10, 11, 13, 15, 17, 18, 22-24, and 26 exhibited significant analgesic effects at a dose of 5.0 mg/kg (inhibition rates > 50%). Among them, daublossomins A (1) and F (6) still showed potent analgesic activity even at a lower dose of 0.2 mg/kg with the inhibition rates of 54.4% and 55.2%, respectively. Grayanotoxin III (20) showed more potent analgesic activities than the positive control, morphine, at a dose of 0.04 mg/kg. A preliminary structure-activity relationship for the analgesic grayanane diterpenoids was discussed, providing some useful clues to design and develop structurally novel potent analgesics.

Synthesis, In vivo Biological Evaluation and Molecular Docking Study of some newer Oxadiazole Derivatives as Anticonvulsant, Antibacterial and Analgesic agents

BACKGROUND

The compounds containing heterocyclic cores with O, N and/or S atoms are bioactive and valuable molecules in the field of drug discovery and development. There are several applications in different areas for the molecules having oxadiazole moiety in their structures viz. herbicides and corrosion inhibitors, electron-transport materials, polymers and luminescent materials. Hence, demand for new anticonvulsant, antibacterial and analgesic agents has turned into an imperative assignment in the area of medicinal chemistry to improve therapeutic efficacy as well as safety.

METHOD

In the journey of new anticonvulsive, antibacterial and analgesic molecules with better potency, some newer Oxadiazole analogues were attained by a sequence of synthetic steps with the substituted acrylic acids. IR and 1H-NMR spectral data were used for the structure elucidation of obtained chemical compounds. In this perspective, the anticonvulsant, antibacterial and analgesic activities were evaluated for synthetically obtained newer chemical moieties. Furthermore, a molecular docking study was performed to elucidate the binding modes of synthesized ligands in the active pockets of Cox-1/2 enzymes, DNA Gyrase and GABA inhibitors.

RESULT

It has been observed that all the synthetic molecules showed good analgesic activity while A1 molecule demonstrated better analgesic activity. In the case of anticonvulsant and antibacterial activity among other ligands, C1 molecule possessed profound anticonvulsant activity whereas B1 molecule showed maximum antibacterial activity and molecular docking study also endorsed the same consequences.

CONCLUSION

It might be recognized from the present study that prepared compounds are distinctive in lieu of their structure and noticeable biological activity. In the quest for a newer group of anticonvulsant, antibacterial and analgesic molecules, these compounds might be useful for the society.

(+)/(-)-Yanhusamides A-C, three pairs of unprecedented benzylisoquinoline-pyrrole hetero-dimeric alkaloid enantiomers from Corydalis yanhusuo

A chemical investigation on the aqueous extract of Corydalis yanhusuo tubers led to the isolation and structural elucidation of three pairs of trace enantiomeric hetero-dimeric alkaloids, (+)/(-)-yanhusamides A-C (1-3), featuring an unprecedented 3,8-diazatricylco[5.2.2.0^2,6]undecane-8,10-diene bridged system. Their structures were exhaustively characterized by X-ray diffraction, comprehensive spectroscopic data analysis, and computational methods. Guided by the hypothetical biosynthetic pathway for 1-3, a gram-scale biomimetic synthesis of (±)-1 was achieved in 3 steps using photoenolization/Diels-Alder (PEDA) [4+2] cycloaddition. Compounds 1‒3 exhibited potent inhibition of NO production induced by LPS in RAW264.7 macrophages. The in vivo assay showed that oral administration of 30 mg/kg of (±)-1 attenuated the severity of rat adjuvant-induced arthritis (AIA). Additionally, (±)-1 induced a dose-dependent antinociceptive effect in the acetic acid-induced mice writhing assay.

Bispecific sigma-1 receptor antagonism and mu-opioid receptor partial agonism: WLB-73502, an analgesic with improved efficacy and safety profile compared to strong opioids

Opioids are the most effective painkillers, but their benefit-risk balance often hinder their therapeutic use. WLB-73502 is a dual, bispecific compound that binds sigma-1 (S1R) and mu-opioid (MOR) receptors. WLB-73502 is an antagonist at the S1R. It behaved as a partial MOR agonist at the G-protein pathway and produced no/unsignificant β-arrestin-2 recruitment, thus demonstrating low intrinsic efficacy on MOR at both signalling pathways. Despite its partial MOR agonism, WLB-73502 exerted full antinociceptive efficacy, with potency superior to morphine and similar to oxycodone against nociceptive, inflammatory and osteoarthritis pain, and superior to both morphine and oxycodone against neuropathic pain. WLB-73502 crosses the blood-brain barrier and binds brain S1R and MOR to an extent consistent with its antinociceptive effect. Contrary to morphine and oxycodone, tolerance to its antinociceptive effect did not develop after repeated 4-week administration. Also, contrary to opioid comparators, WLB-73502 did not inhibit gastrointestinal transit or respiratory function in rats at doses inducing full efficacy, and it was devoid of proemetic effect (retching and vomiting) in ferrets at potentially effective doses. WLB-73502 benefits from its bivalent S1R antagonist and partial MOR agonist nature to provide an improved antinociceptive and safety profile respect to strong opioid therapy.

Monoterpenoid indole alkaloids isolated from the stems and twigs of Strychnos cathayensis

Seven undescribed monoterpenoid indole alkaloids, two N(4)-chloromethylation artifacts, and 10 known alkaloids were isolated from the stems and twigs of Strychnos cathayensis. The corresponding structures were elucidated via spectroscopic data interpretation and electronic circular dichroism. The absolute configuration of (17S)-12-hydroxy-11-methoxydiaboline, the major anomer of 12-hydroxy-11-methoxydiaboline, was characterized by X-ray diffraction analysis for the first time. At an intraperitoneal dose of 30 mg/kg, 12-hydroxy-11-methoxy-N(4)-chloromethyldiaboline and (-)-macusine A exhibited potential analgesic effects with prolongation rates of 99% and 47% for the latency time of hind-paw licking, respectively, compared to the blank control. 12-Hydroxy-11-methoxydiaboline, 12-hydroxy-11-methoxydiaboline N(4)-oxide, retuline N-oxide, and (-)-vincosamide exhibited antiviral activity against Coxsackie virus B3 (CVB3) with IC₅₀ values of 33.33 μM.

Design, synthesis, and biological evaluation of low-toxic lappaconitine derivatives as potential analgesics

The C₁₈-diterpenoid alkaloid lappaconitine (LA) is a non-addictive analgesic used in China. The toxicity (LD₅₀ = 11.7 mg/kg) limits its application. Two series of LA derivatives, including amides and sulfonamides (1-93), were designed and synthesized by modification on their C4 acetamidobenzoate side chains in this work. In vivo analgesic activity and toxicity of all derivatives were evaluated, and the structure-activity relationship was summarized. Six lead compounds (35, 36, 39, 49, 70, and 89) exhibited approximate analgesic activity to LA but with significantly reduced toxicity. The therapeutic index of these compounds is 14-30 times that of LA. In vivo metabolism study of the lead compounds 39, 49, 70, and 89 were conducted by UPLC-MS^E, indicating the reason for the low toxicity of the potential derivatives might be they are difficult to metabolize to toxic metabolite N-deacetyllappaconitine compared to LA. The effects of lead compounds on sodium channels and hERG channels were also studied by ion channel reader (ICR) which further revealed their analgesic and toxicity-attenuating mechanisms. Sodium channel assay revealed that the analgesic mechanism of these lead compounds was inhibiting the Na_v 1.7 channels. Taken together, compound 39 was provided as a new analgesic lead compound with significantly low toxicity and comparable activity to LA.

Fimbristylis aestivalis Vahl: a potential source of cyclooxygenase-2 (COX-2) inhibitors

Cyclooxygenase-2 (COX-2) is an inducible enzyme that accelerates the biosynthesis of PGs during inflammation and has emerged as an important therapeutic target for anti-inflammatory drugs. Natural compounds may serve as a source of inspiration for pharmaceutical chemists and a foundation for developing innovative COX-2 inhibitors with fewer side effects. Therefore, the objective of this study was to identify the potent COX-2 inhibitor and anti-inflammatory activity of the Fimbristylis aestivalis whole plant extract (FAWE). The plant extract was found dominant with rosmarinic acid followed by catechin hydrate, syringic acid, rutin hydrate, (-) epicatechin, quercetin, myricetin, and catechol. FAWE exhibited considerable dose-dependent analgesic efficacy in all analgesic test models. FAWE also showed promising anti-inflammatory potential in carrageenan-induced inflammations in mice. This result was corroborated by molecular docking, revealing that the aforesaid natural polyphenols adopt the same orientation as celecoxib in the COX-2 active site. On the other hand, molecular dynamics (MD) simulations were performed between the most abundant components (rosmarinic acid, catechin hydrate, and syringic acid) and COX-2. Based on hydrogen bonding, RMSD, RMSF, radius of gyration, PCA, and Gibbs free energy landscape analysis, the results demonstrated that these compounds are very stable in the active site of COX-2, indicating substantial COX-2 inhibitory activity.

Evaluation of analgesic and anti-inflammatory activity of purine-2,6-dione-based TRPA1 antagonists with PDE4/7 inhibitory activity

Background

To verify the validity of the proposed pain treatment approach, which is based on concomitant blocking of the Transient Receptor Potential Ankyrin 1 (TRPA1) channel and phosphodiesterases (PDEs) 4B/7A activity, we continued our pharmacological studies on 8-alkoxypurine-2,6-diones selected based on previous in vitro screening.

Methods

Derivatives 17, 31, and 36 were pharmacologically evaluated in vivo using the formalin test and oxaliplatin-induced neuropathic pain: the von Frey and the cold plate tests, and in the carrageenan-induced edema model. Compound 36, which turned out to be the most promising, was further evaluated in the collagen-induced arthritis model. The pharmacokinetic parameters of this compound were also estimated.

Results

All the tested compounds exhibited significant analgesic and anti-inflammatory activities. Compound 36 was additionally characterized by an antiarthritic effect and showed a favorable pharmacokinetic profile in rats.

Conclusion

The compounds evaluated in this study represent a new class of derivatives with analgesic and anti-inflammatory activities that involve TRPA1 antagonism and PDE4/7 inhibition.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-022-00397-6.

An Overview of Synthetic Routes of Pharmaceutically Important Pyranopyrazoles

Pyranopyrazoles are bicyclic nitrogen-containing heterocycles having broad spectrum bioactivities, which may act as anti-cancer, anti-inflammatory, antibacterial, antifungal, insecticidal and molluscicidal agents. Pyranopyrazoles have become an attractive scaffold for the discovery of new drugs due to the diverse range of bioactivities associated to this nucleus. In this review, we have focused on medicinal importance of pyranopyrazole derivatives and have also highlighted different routes for the synthesis of pyranopyrazole derivatives using inexpensive and commonly available and starting materials.

Potent CaV3.2 channel inhibitors exert analgesic effects in acute and chronic pain models

Pain is the most common presenting physical symptom and a primary reason for seeking medical care, which chronically affects people's mental health and social life. Ca_V3.2 channel plays an essential role in the peripheral processing maintenance of pain states. This study was designed to identify novel drug candidates targeting the Ca_V3.2 channel. Whole-cell patch-clamp, cellular thermal shift assay, FlexStation, in vivo and in vitro Ca_V3.2 knock-down, site-directed mutagenesis, and double-mutant cycle analysis were employed to explore the pain-related receptors and ligand-receptor direct interaction. We found that toddaculin efficiently inhibits the Ca_V3.2 channel and significantly reduced the excitability of dorsal root ganglion neurons and pain behaviors. The Carbonyl group of coumarins directly interacts with the pore domain of Ca_V3.2 via van der Waals (VDW) force. Docking with binding pockets further led us to identify glycycoumarin, which exhibited more potent inhibition on the Ca_V3.2 channel and better analgesic activity than the parent compound. Toddaculin and its analog showed beneficial therapeutic effects in pain models. Toddaculin binding pocket on Ca_V3.2 might be a promising docking site for the design of drugs.

Methionine 58 is a key residue in the modulation of BmK scorpion toxin AGP-SYPU2 activity through in silico and in vivo studies

Protein dynamic networks play an important role in the regulation of many protein systems. Some residues that are far away from the interface between proteins and their targets have a critical role in modulating the activity of some scorpion toxins. Here, conservation analysis combined with an in vivo experiment has reveals that Met58 is a key residue of BmK scorpion toxin AGP-SYPU2 in the modulation of analgesic activity. Molecular dynamics simulations clearly reveal the conformational changes that allow the loop between the β2 and β3 sheets to be exposed on the toxin surface to interact with its targets. Our results emphasize specific roles for the residue Met58 in the NC domain and our work gives valuable information for further modification of scorpion toxins to obtain new analgesic peptides with enhanced activity. Communicated by Ramaswamy H. Sarma.

Diterpenoid alkaloids from the whole herb of Delphinium grandiflorum L

Seven previously undescribed diterpenoid alkaloids, eight reaction products and thirteen known compounds were isolated from the whole plant of Delphinium grandiflorum L. (Ranunculaceae). Grandiflonines A and B have an unprecedented C₂₀-diterpenoid alkaloid skeleton, which features inversion of the configuration of C-18. Their structures were determined by comprehensive analyses of spectroscopic data, X-ray diffraction and Mosher's method. The probable biosynthetic pathway of grandiflonine A was discussed. Additionally, the analgesic activity and anti-inflammatory activity by inhibition of NO production were evaluated. Among them, deoxylappaconitine (ED₅₀ = 0.35 mg/kg, TI = 46.22) showed significant analgesic activity that was superior to the reference drug lappaconitine (ED₅₀ = 3.5 mg/kg, TI = 3.34).

Isolation, identification, and activity evaluation of diterpenoid alkaloids from Aconitum sinomontanum

A phytochemical study led to the isolation of 25 diterpenoid alkaloids from Aconitum sinomontanum, of which six were described for the first time. Among them compounds 1-3 are anhydrolycoctonine derivatives, rare rearranged aconitine-type C₁₉-diterpenoid alkaloids. To our best knowledge, less than ten of this type of alkaloids were isolated just from the genus Aconitum. The structures of these unreported compounds were elucidated by extensive analysis of NMR spectroscopic data and X-ray diffraction. The biological activities of compounds 1-3, 5-9, and 12-25 were evaluated. Among the tested compounds, compounds 2 and 17 showed potent inhibitory effect on the capsaicin (selective TRPV1 agonist) mediated activation of transient receptor potential vanilloid 1 (TRPV1) channels expressed in HEK-293 cells with inhibition rate of 31.78% and 30.94% at the concentration of 10 μM. Compounds 1-3, 5-9, 13, and 18-25 exhibited weak cytotoxic activity against human tumor cell lines NCI-H226 and MDA-MB-231 with inhibition rate over 10% at the concentration of 10 μM. Compound 16 showed most inhibitory effect on the expression of Nrf2 (NF-E2-related factor-2)-regulated gene with inhibition rate of 25% at the concentration of 20 μM.

Pharmacological evaluation of the gabapentin salicylaldehyde derivative, gabapentsal, against tonic and phasic pain models, inflammation, and pyrexia

Gabapentinoids are effective drugs in most animal models of pain and inflammation with variable effects in humans. The current study evaluated the pharmacological activity of gabapentin (GBP) and its salicylaldehyde derivative (gabapentsal; [2-(1-(((2-hydroxybenzylidene) amino) methyl) cyclohexyl) acetic acid]; GPS) in well-established mouse models of nociceptive pain, inflammatory edema, and pyrexia at doses of 25-100 mg/kg. GPS allayed tonic visceral pain as reflected by acetic acid-induced nociception and it also diminished thermally induced nociception as a mimic of phasic thermal pain. Antagonism of GPS-induced antinociceptive activities by naloxone (NLX, 1.0 mg/kg, subcutaneously, s.c), beta-funaltrexamine (β-FNT, 5.0 mg/kg, s.c), naltrindole (NT, 1.0 mg/kg, s.c), and nor-binaltorphimine (NOR-BNI, 5.0 mg/kg, s.c), and pentylenetetrazole (PTZ-15 mg/kg, intraperitoneally, i.p) implicated an involvement of both opioidergic and GABAergic mechanisms. Tail immersion test was conducted in order to delineate the mechanistic insights of antinociceptive response. Inflammatory edema induced by carrageenan, histamine, or serotonin was also effectively reversed by GPS in a fashion analogous to aspirin (150 mg/kg, i.p), chlorpheniramine (1.0 mg/kg, i.p), and mianserin (1.0 mg/kg, i.p), respectively. Additionally, yeast-induced pyrexia was decreased by GPS in a comparable manner to acetaminophen (50 mg/kg, i.p). These observations suggest that GPS possesses ameliorative properties in tonic, phasic, and tail immersion tests of nociception via opioidergic and GABAergic mechanisms, curbs inflammatory edema, and is antipyretic in nature.

A novel ω-conotoxin Bu8 inhibiting N-type voltage-gated calcium channels displays potent analgesic activity

ω-Conotoxins inhibit N-type voltage-gated calcium (Ca_V2.2) channels and exhibit efficacy in attenuating neuropathic pain but have a low therapeutic index. Here, we synthesized and characterized a novel ω-conotoxin, Bu8 from Conus bullatus, which consists of 25 amino acid residues and three disulfide bridges. Bu8 selectively and potently inhibits depolarization-activated Ba²⁺ currents mediated by rat Ca_V2.2 expressed in HEK293T cells (IC₅₀ = 89 nmol/L). Bu8 is two-fold more potent than ω-conotoxin MVIIA, a ω-conotoxin currently used for the treatment of severe chronic pain. It also displays potent analgesic activity in animal pain models of hot plate and acetic acid writhing but has fewer side effects on mouse motor function and lower toxicity in goldfish. Its lower side effects may be attributed to its faster binding rate and higher recovery ratios. The NMR structure demonstrates that Bu8 contains a small irregular triple β-strand. The structure-activity relationships of Bu8 Ala mutants and Bu8/MVIIA hybrid mutants demonstrate that the binding mode of Ca_V2.2 with the amino acid residues in loop 1 and loop 2 of Bu8 is different from that of MVIIA. This study characterizes a novel, more potent ω-conotoxin and provides new insights for designing Ca_V2.2 antagonists.

Betulinic Acid-Azaprostanoid Hybrids: Synthesis and Pharmacological Evaluation as Anti-inflammatory Agents

Background: Prevention and treatment of chronic inflammatory diseases require effective and low-toxic medicines. Molecular hybridization is an effective strategy to enhance the biological activity of new compounds. Triterpenoid scaffolds are in the focus of attention owing to their anti-inflammatory, antiviral, antiproliferative, and immunomodulatory activities. Heteroprostanoids have different pleiotropic effects in acute and chronic inflammatory processes.

Objective: The study aimed to develop structurally new and low toxic anti-inflammatory agents via hybridization of betulinic acid with azaprostanoic acids.

Methods: A series of betulinic acid-azaprostanoid hybrids was synthesized. The synthetic pathway included the transformation of betulin via Jones' oxidation into betulonic acid, reductive amination of the latter and coupling obtained by 3β-amino-3-deoxybetulinic acid with the 7- or 13-azaprostanoic acids and their homo analogues. The hybrids 1-9 were investigated in vivo on histamine-, formalin- and concanavalin A-induced mouse paw edema models and two models of pain - the acetic acid-induced abdominal writhing and the hot-plate test. The hybrids were in vitro evaluated for cytotoxic activity on cancer (MCF7, U-87 MG) and non-cancer humane cell lines.

Results: In the immunogenic inflammation model, the substances showed a pronounced anti-inflammatory effect, which was comparable to that of indomethacin. In the models of the exudative inflammation, none of the compounds displayed a statistically significant effect. The hybrids produced weak or moderate analgesic effects. All the agents revealed low cytotoxicity on human immortalized fibroblasts and cancer cell lines compared with 3β-amino-3-deoxybetulinic acid and doxorubicin.

Conclusion: The results indicate that the principal anti-inflammatory effect of hybrids is substantially provided with the triterpenoid scaffold and in some cases with the azaprostanoid scaffold, but the latter makes a significant contribution to reducing the toxicity of hybrids. Hybrid 1 is of interest as a potent low toxic agent against immune-mediated inflammation.

Chemoenzymatic synthesis of 2,6-disubstituted tetrahydropyrans with high σ1 receptor affinity, antitumor and analgesic activity

1,3-Dioxanes 1 and cyclohexanes 2 bearing a phenyl ring and an aminoethyl moiety in 1,3-relationship to each other represent highly potent σ1 receptor antagonists. In order to increase the chemical stability of the acetalic 1,3-dioxanes 1 and the polarity of the cyclohexanes 2, tetrahydropyran derivatives 3 equipped with the same substituents were designed, synthesized and pharmacologically evaluated. The key step of the synthesis was a lipase-catalyzed enantioselective acetylation of the alcohol (R)-5 leading finally to enantiomerically pure test compounds 3a-g. With respect to σ1 receptor affinity and selectivity over a broad range of related (σ2, PCP binding site) and further targets, the enantiomeric benzylamines 3a and cyclohexylmethylamines 3b represent the most promising drug candidates of this series. However, the eudismic ratio for σ1 binding is only in the range of 2.5-3.3. Classical molecular dynamics (MD) simulations confirmed the same binding pose for both the tetrahydropyran 3 and cyclohexane derivatives 2 at the σ1 receptor, according to which: i) the protonated amino moiety of (2S,6R)-3a engages the same key polar interactions with Glu172 (ionic) and Phe107 (π-cation), ii) the lipophilic parts of (2S,6R)-3a are hosted in three hydrophobic regions of the σ1 receptor, and iii) the O-atom of the tetrahydropyran derivatives 3 does not show a relevant interaction with the σ1 receptor. Further in silico evidences obtained by the application of free energy perturbation and steered MD techniques fully supported the experimentally observed difference in receptor/ligand affinities. Tetrahydropyrans 3 require a lower dissociative force peak than cyclohexane analogs 2. Enantiomeric benzylamines 3a and cyclohexylmethylamines 3b were able to inhibit the growth of the androgen negative human prostate cancer cell line DU145. The cyclohexylmethylamine (2S,6R)-3b showed the highest σ1 affinity (Ki(σ1) = 0.95 nM) and the highest analgesic activity in vivo (67%).

Phytochemical profiling, in vitro and in vivo anti-inflammatory, analgesic and antipyretic potential of Sesuvium sesuvioides (Fenzl) Verdc. (Aizoaceae)

Sesuvium sesuvioides (Fenzl) Verdc is traditionally used in the treatment of inflammatory diseases such as arthritis and gout The aim of present study was to assess the possible anti-inflammatory, analgesic and antipyretic potential of the methanol extract of Sesuvium sesuvioides (SsCr) to prove scientifically its folklore use in the inflammatory diseases and to screen its total antioxidant capacity by multiple methods and phytocompounds by GC-MS. The preliminary phytochemical studies showed the presence of phenols, flavonoids, glycosides, coumarin, terpenoids, saponins, fats and carbohydrates in crude extract. The total phenolic contents (27.31 ± 0.28 mg GAE/g) and total flavonoids (3.58 ± 0.12 mgRE/g) values were observed. The antioxidant capacity of SsCr showed significant DPPH, ABTS, CUPRAC, FRAP, PBD and metal chelating results. GC-MS analysis displayed the phytoconstituents with anti-inflammatory potentials such as 2-methoxy-4-vinylphenol, vanillin, umbelliferone, methyl ferulate, palmitoleic acid, methyl palmitate and phytol. SsCr presented noteworthy HRBC membrane stability with maximum inhibition of cell hemolysis (47.79%). In carrageenan-induced hind paw edema assay result showed dose-dependent anti-inflammatory action. SsCr presented significant (p < 0.05) analgesic activity in hot-plate and tail flicking tests similarly it also showed the noteworthy inhibition in pain latency against formalin induced analgesia at 1st and 2nd phases. SsCr reduced the acetic acid-induced writhes at different doses (250, 500 and 750 mg). Results of antipyretic activity of SsCr extract were significant at 500 and 750 mg. The results of in vitro and in vivo experimental studies verified the anti-inflammatory, analgesic and antipyretic potential of Sesuvium sesuvioides and supported the folklore uses of this plant.

Pharmacological investigation of analgesic and antipyretic activities of methanol extract of the whole part of Aeginetia indica

ETHNOPHARMACOLOGICAL RELEVANCE

Aeginetia indica (Linn.), commonly known as aankuri bankuri, guan-jen-huang, forest ghost flower, dok din daeng, dapong tubo; is a root parasitic plant of the Orobanchaceae family native to South and South-East Asian region. Different parts of the plant are traditionally used to treat fever, pain, inflammation, arthritis, cough, diabetes, and chronic liver disease. Local practitioners often recommend this plant as a folk remedy for dermal swelling, painful menstrual periods, wounds, and knee pain. However, the antipyretic and analgesic activity of A. indica have never been investigated.

AIM OF THE STUDY

The present study was aimed to evaluate the analgesic and antipyretic potential of Aeginetia indica plant extract to verify its effectiveness as reported in traditional uses.

MATERIALS AND METHODS

Preliminary phytochemical analysis of Aeginetia indica crude extract was performed using previously established methods and antioxidant capacity was determined by phosphomolybdenum assay. In vivo analgesic activity of Aeginetia indica methanol extract (AiME) was evaluated by acetic acid-induced writhing test, formalin-induced paw licking test, and hot plate test model. The antipyretic activity was studied in Baker's yeast induced pyrexia model.

RESULTS

Phytochemicals screening revealed cardiac glycosides, saponins, phenols, tannins, and flavonoids in the crude extract of Aeginetia indica. Total phenolic and flavonoid content were recorded as 101 ± 1.1 mg GAE/g of the extract and 35 ± 0.8 mg QE/g of the extract, respectively. The total antioxidant capacity observed in phosphomolybdenum assay was 68.3 ± 1.3 mg ascorbic acid equivalent per gram of the extract. AiME showed significant dose-dependent analgesic activity against acetic acid-induced writhing, formalin-induced paw licking, and hot plate pain model. A higher dose of A. indica (200 mg/kg) produced significant (P < 0.001) inhibition of writhing by 69% whereas, standard aspirin showed maximum 85.6% inhibition. AiME at all doses showed a significant (P < 0.001) decrease of paw licking time in both early neurogenic and late inflammatory pain phase of formalin-induced licking test. In the hot plate test, AiME at a 200 mg/kg dose produced antinociceptive activity (55.18%) higher than the standard ketorolac (49.88%) at 1 h. However, after 2 h, ketorolac showed a maximum effect of 62.66% and AiME 200 mg/kg showed a 60.24% effect. A significant (P < 0.001) reduction of rectal temperature (4.54 °F↓) was recorded for AiME 200 mg/kg, which was higher than the standard paracetamol (3.86 F°↓) after 24 h of treatment.

CONCLUSION

The in vivo investigational studies' results demonstrated promising analgesic and antipyretic activities of A. indica, which supported the claim of its folk uses.

Diverse isoquinolines with anti-inflammatory and analgesic bioactivities from Hypecoum erectum

ETHNOPHARMACOLOGICAL RELEVANCE

Hypecoum erectum has been used extensively in folk medicine to treat inflammation, fever, and pain. However, few investigations have been carried out on the biological activities related to its traditional use. The chemical constituents of this plant along with their anti-inflammatory and analgesic effects have yet to be revealed.

AIM OF THE STUDY

This study aimed to support the traditional use of H. erectum by first assessing its anti-inflammatory and analgesic effects and then investigating its chemical constituents to identify any anti-inflammatory and/or analgesic compounds.

MATERIAL AND METHODS

The in vivo anti-inflammatory and analgesic activities of the MeOH extract (ME), total alkaloid (AL), and non-alkaloid (Non-AL) fractions of H. erectum at doses of 200, 100, and 50 mg/kg and four major constituents (20, 21, 22, and 27) at doses of 100 and 50 mg/kg delivered via intragastrical administration were evaluated using carrageenan-induced paw edema and acetic acid-stimulated writhing animal models. A phytochemical study of the bioactive (AL) fraction was conducted using various chromatographic techniques, and the structures of the obtained isoquinolines were identified by multiple spectroscopic analyses and quantum chemical computations. Moreover, the anti-inflammatory activities of all the isolates were assessed in vitro based on the suppression of lipopolysaccharide-activated inflammatory mediators (COX-2, IL-1β, and TNF-α) in RAW 264.7 macrophage cells.

RESULTS

At the dose of 200 mg/kg, the three fractions (ME, AL, and Non-AL) of H. erectum ameliorated the paw edema by carrageenan-stimulated and reduced the number of writhing by acetic acid-induced in mice compared to the model group, with the AL fraction showing the most potent effects. Subsequent phytochemical investigation of the AL fraction led to the isolation of six new isoquinoline alkaloids (1-6) as well as 23 known analogues (7-29). However, compared to common isoquinolines, compounds 1-4 possess an additional nitrogen atom, while compound 5 has two additional nitrogen atoms. These additional atoms enrich the diversity of natural isoquinoline alkaloids. Further pharmacological evaluation in vivo revealed that the four major constituents (20, 21, 22, and 27) significantly relieved paw edema at 100 mg/kg, while protopine (20) and oxyhydrastinin (27) remarkably decreased the number of writhing at 100 mg/kg. In addition, most of the isolates displayed anti-inflammatory effects, as indicated by the inhibition of inflammatory mediators (COX-2, IL-1β, and/or TNF-α) in vitro at a treatment concentration of 5 μg/mL. trans-benzindenoazepines (13), protopine (20), and 1,3,6,6-tetramethyl-5,6,7,8-tetrahyboisoquiolin-8-one (25) showed comparable anti-inflammatory activity to dexamethasone by inhibiting the secretion of IL-1β.

CONCLUSIONS

This investigation validated the traditional use of H. erectum by assessing its anti-inflammatory and analgesic effects. Phytochemical investigation revealed the diversity and novelty of the natural isoquinoline alkaloids in H. erectum. Four major isoquinolines were identified as the bioactive constituents of H. erectum. The findings provide scientific justification to support the traditional application of H. erectum for treating inflammatory and pain disorders.

C19-diterpenoid alkaloids from the rhizomes of Aconitum pendulum

Six new C₁₉-aconitine-type diterpenoid alkaloids, pendulumines A-F (1-6), together with six known ones (7-12), were isolated from the rhizomes of Aconitum pendulum. Their structures were elucidated using extensive spectroscopic data analysis, including 1D and 2D NMR, MS, and single-crystal X-ray diffraction analysis. The isolates were also tested for their analgesic activity based on the thermal avoidance response of the roundworm Pirstionchus pacificus, and 9 showed significant biological activity with an EC₅₀ value of 0.08 ± 0.02 mg.mL^-1.

Discovery and characterization of the novel conotoxin Lv1d from Conus lividus that presents analgesic activity

Cone snails are predatory gastropod mollusks that are distributed in all tropical marine environments and contain small peptides (conotoxins) in their venom to capture prey. However, the biochemical and molecular aspects of conotoxins remain poorly understood. In this article, a novel α4/7-conotoxin, Lv1d, was obtained from the venom duct cDNA library of the worm-hunting Conus lividus collected from the South China Sea. The cDNA of Lv1c encodes a 65 residue conopeptide precursor, which consists of a 21 residue signal peptide, a 27 residue Pro region, and 17 residues of mature peptide. The mature peptide Lv1d was chemically synthesized according to the sequence GCCSDPPCRHKHQDLCG. It was found that 10 μM Lv1d can completely inhibit frog sciatic nerve-gastrocnemius muscle contractility within 60 min. Moreover, 100 μg/kg Lv1d showed good analgesic effects in mouse hot plate model and formalin test. Patch clamp experiments showed that 5 μM Lv1d can inhibit the cholinergic microexcitatory postsynaptic currents (mEPSCs) requency and amplitude of projection neurons in Drosophila. In conclusion, the synthesis of Lv1d and its biological and physiological data might contribute to the development of this peptide as a novel potential drug for therapeutic applications. This finding also expands the knowledge of the targeting mechanism of the α4/7-subfamily conotoxins.

Antioxidant, anti-inflammatory, antibacterial, and analgesic activities and mechanisms of quinolines, indoles and related derivatives

Quinoline, isoquinoline and indoles are common heterocyclic compounds. They have many biological activities, such as antioxidant, anti-inflammatory, antibacterial, antitumor, anti-virus, anti-rheumatism, immunity regulation, expectorant, and analgesic. Over the past few centuries, traditional natural products have made great contributions to the discovery and development of new therapeutic agents. Many important drugs have been found from these three classes of compounds. In this mini-review, we mainly cover the research progress on antioxidant, anti-inflammatory, antibacterial, analgesic activities of quinoline, isoquinoline, and indole compounds over the past 20 years (2000-2019). We aim to explore new characteristic groups or structures in the search for active lead compounds and provide a basis for rational drug design.

Zanthoxylum nitidum (Roxb.) DC: Traditional uses, phytochemistry, pharmacological activities and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum nitidum (Roxb.) DC. (Z. nitidum), which is known in China as Liang-Mian-Zhen, is mainly distributed in southern China and is widely used in traditional Chinese medicine. It is traditionally used for treating stomach ache, toothache, rheumatic arthralgia, traumatic injury and venomous snake bites. Additional medical applications include the treatment of inflammations, various types of cancer, bacterial and viral infections, gastric and oral ulcers and liver damage.

AIM OF THIS REVIEW

This paper aims to offer up-to-date information on the botany, traditional uses, phytochemistry, pharmacology and toxicity of Z. nitidum. This review also discussed the perspectives for possible future research on Z. nitidum.

MATERIALS AND METHODS

A comprehensive review was carried out on studies about Z. nitidum conducted in the past 60 years by using different resources, including Flora of China, Pharmacopoeia of the People's Republic of China and academic databases.

RESULTS

At present, more than 150 chemical constituents have been separated and identified from Z. nitidum, most of which include alkaloids. Biological activities, including anti-inflammation, analgesia, haemostasis, anticancer and antibacterial, were determined via in vitro and in vivo studies. The variations in the efficacy of Z. nitidum can be attributed to the biological activities of its natural products, especially alkaloids. Toxicity studies on Z. nitidum are relatively few, thus requiring further study.

CONCLUSIONS

This article generalises the current research achievements related to Z. nitidum, which is an important medicinal material in China. Some traditional uses of Z. nitidum have been assessed by pharmacological studies. Unresolved problems remain, including molecular mechanisms underlying biological activities, pharmacokinetics, toxicology and therapeutic effect, which are still being studied and explored before Z. nitidum can be integrated into clinical medicine.

Anti-inflammatory and analgesic activities of Neolamarckia cadamba and its bioactive monoterpenoid indole alkaloids

ETHNOPHARMACOLOGICAL RELEVANCE

Neolamarckia cadamba has been used traditionally to treat inflammation, fever, and pruritus in the Dai ethnopharmacy in Yunnan province, P.R. China. However, according to literature survey, the action basis of anti-inflammatory and analgesic activities of this plant were rarely reported, which accounts for the original intentions of this investigation.

AIM OF THE STUDY

The study aimed to investigate the anti-inflammatory and analgesic action of methanolic extract (ME), ethyl acetate (EA), and aqueous (AQS) fractions of N. cadamba and further explore the accurate compounds responsible for the activities of EA fraction.

MATERIALS AND METHODS

The in vivo anti-inflammatory and analgesic activities of ME, EA, and AQS fractions at the doses of 200 and 400 mg/kg and two major constituents (compounds 5 and 7) at 50 and 100 mg/kg via intragastrically administrated, respectively, were evaluated by carrageenan-induced paw edema and acetic acid-stimulated writhing animal models. Aspirin (ASP) was used as the positive control at the dose of 200 mg/kg. The monoterpenoid indole alkaloids (MIAs) in EA fraction were phytochemically studied utilizing chromatographic techniques, and their structures and absolute configurations were established on the basis of multiple spectroscopic analyses and quantum computational chemistry method. Moreover, the in vitro anti-inflammatory activities of all the isolates were assessed by suppressing releases of LPS-activated inflammatory mediators (TNF-α, IL-1β, and COX-2) in RAW 264.7 macrophage cells at a concentration of 10 μg/mL. Dexamethasone (DXM) was used as the positive control.

RESULTS

Three fractions (ME, EA, and AQS) significantly ameliorated the paw edema caused by carrageenan and reduced the number of writhing induced by acetic acid in comparison to the control group at the doses of 200 and/or 400 mg/kg (in vivo). Subsequent phytochemical investigation of EA fraction led to the structural characterization of four new monoterpenoid indole alkaloids, neocadambines A-D (1-4), as well as eight known analogues (5-12). Neocadambine A possesses a novel 14-nor-MIA skeleton that could be derived from the corynantheine-type MIAs via oxidative cleavage of C3-C14 bond and subsequently degradation of C14. Moreover, the structure of a bioactive known MIA, cadambine acid (6), was reassigned by analysis of its NMR spectroscopic data. Further biological assays revealed that the major constituent 3β-dihydrocadambine (7) significantly relieved the paw edema and decreased the number of writhing at 100 mg/kg in vivo. In addition, most of the isolates displayed remarkable in vitro anti-inflammatory effects by inhibiting the secretion of aforementioned inflammatory mediators (COX-2, IL-1β, and TNF-α) at a concentration of 10 μg/mL, and compounds 4, 7, and 9 showed better anti-inflammatory effects than that of positive control, dexamethasone.

CONCLUSIONS

This study further validated the anti-inflammatory and analgesic activities of N. cadamba, and revealed that monoterpenoid indole alkaloids could partly contribute to the efficacy of this ethnodrug. The major constituent 3β-dihydrocadambine (7) showed significant anti-inflammatory activities both in vitro and in vivo, which suggested that it could be a promising anti-inflammatory lead compound. Our findings provided scientific justification to support the traditional application of N. cadamba for treating inflammatory and nociceptive disorders.

Pharmacological evaluation of analgesic, anti-inflammatory and antipyretic activities of ethanolic extract of Indigofera argentea Burm. f

ETHNOPHARMACOLOGICAL RELEVANCE

Indigofera argentea Burm. f.; commonly known as neel, jantari, hathio; is traditionally used for the treatment of headache, fever, inflammation and body pain. Local communities also used this plant for the treatment of malaria, jaundice, vertigo and gastric disorders.

AIM OF THE STUDY

This study is aimed to evaluate the toxicity and possible analgesic, anti-inflammatory and antipyretic activities of the ethanolic crude extract of Indigofera argentea (IaCr) to support its use in folk medicine and to screen the phytochemical constituents and antioxidant activity.

MATERIALS AND METHODS

Aqueous ethanolic (30:70) extract of whole plant of Indigofera argentea (IaCr) was prepared and phytochemical study was performed by preliminary methods followed by HPLC and DPPH method. In vivo experiments were performed in Wistar albino rats including hot plate, tail immersion, formalin and capsaicin-induced pain tests in rats and acetic acid-induced writhing test in mice. Anti-inflammatory activity was assessed by using in vitro human red blood cell (HRBC) membrane stabilization and carrageenan-induced rat paw edema test, while antipyretic activity was evaluated by Brewer's yeast-induced pyrexia test.

RESULTS

The crude extract of Indigofera argentea confirmed the presence of flavonoids, glycosides, alkaloids, saponins and tannins as soluble ethanolic constituents in preliminary study. The maximum quantity of gallic acid equivalent (GAE) phenolics, and quercetin equivalent (QE) flavonoid content found was 81 ± 2 mg GAE/g and 56 ± 1.4 mg QE/g of extract respectively. Quantification based on HPLC exposed the presence of phenols and flavonoids, quercetin, gallic acid, caffeic acid, chlorogenic acid, benzoic acid, ferulic acid and coumaric acid. In vivo experiments revealed significant P < 0.05) dose-dependent inhibition in hot plate, tail immersion and capsaicin-induced pain test. IaCr showed significant inhibition of pain latency against both phases in formalin test and considerably decreased the number of writhes caused by acetic acid at the doses of 30, 100 and 300 mg/kg. In the in vitro anti-inflammatory (HRBC) assay, IaCr showed good membrane stability with maximum percentage hemolysis inhibition of 49.29% while in carrageenan-induced paw edema test in rats the IaCr showed significant anti-inflammatory action in a dose-dependent fashion. Statistical significant reduction in rectal temperature was observed at the doses of 100 and 300 mg/kg in yeast-induced pyrexia test in rats.

CONCLUSION

The results of the experimental studies proved the analgesic, anti-inflammatory and antipyretic activities of Indigofera argentea and supported the traditional use of this plant.

Preparation and in vitro / in vivo evaluation of flurbiprofen nanosuspension-based gel for dermal application

Flurbiprofen (FB) is an analgesic and anti-inflammatory drug, but its low water solubility (BCS Class II) limits its dermal bioavailability. The aim of this study is to develop a FB nanosuspension (NS) based gel and to evaluate its analgesic and anti-inflammatory activities in rats. FB-NS was produced by the wet milling method with Plantacare 2000^Ⓡ, as stabilizer. The FB-NS was then incorporated in different carrier gels such as hydroxypropyl methyl cellulose (HPMC), polycarbophil, oleogel, and chitosan. To select the optimum gel type, visual examinations, pH and rheological property measurements, texture profile analysis, in vitro release and ex vivo permeation studies were performed. Following these tests, the analgesic and anti-inflammatory activities of the optimum NS based gel were evaluated using the tail flick and carrageenan-induced paw edema methods consecutively. The NS was successfully prepared with the wet milling method, and the PS, PDI and ZP values were found to be 237.7 ± 6.8 nm, 0.133±0.030, and -30.4 ± 0.7 mV; respectively. Among the NS-based gels, HPMC gel showed more suitable rheological and mechanical properties, also the percentage of permeated FB and the flux value observed for HPMC gel were higher for HPMC than for the other gels. Thus, HPMC gel was selected as a carrier gel for in vivo pharmacodynamics studies. The anti-inflammatory activity of FB-NS HPMC gel was higher than that of the physical mixture gel and that of the coarse suspension gel. Results of our analgesic activity studies showed that, in the 180th min of FB nanosuspension treatment, the latency time was significantly prolonged compared to that of the control group (p<0.05). As a conclusion, while nanosuspensions increased the in vivo pharmacodynamics effect of FB by means of nanosized particles and a large surface area, the HPMC gel as a carrier prolonged the contact time of NSs with skin and eased the dermal application.

Multiple biological active 4-aminopyrazoles containing trifluoromethyl and their 4-nitroso-precursors: Synthesis and evaluation

4-Nitroso-3-trifluoromethyl-5-alkyl[(het)aryl]pyrazoles were synthesized via one-pot nitrosation of 1,3-diketones or their lithium salts followed by treatment of hydrazines. Reduction of nitroso-derivatives made it possible to obtain 4-amino-3-trifluoromethylpyrazoles chlorides. According to computer-aided calculations, all synthesized compounds are expected to have acceptable ADME profile for drug design. Tuberculostatic, antibacterial, antimycotic, antioxidant and cytotoxic activities of the compounds were evaluated in vitro, while their analgesic and anti-inflammatory action was tested in vivo along with acute toxicity studies. N-Unsubstituted 4-nitrosopyrazoles were the most effective tuberculostatics (MIC to 0.36 μg/ml) and antibacterial agents against Streptococcus pyogenes (MIC to 7.8 μg/ml), Staphylococcus aureus,S. aureus MRSA and Neisseria gonorrhoeae (MIC to 15.6 μg/ml). 4-Nitroso-1-methyl-5-phenylpyrazole had the pronounced antimycotic action against a wide range of fungi (Trichophytonrubrum, T. tonsurans, T. violaceum, T. interdigitale, Epidermophytonfloccosum, Microsporumcanis with MIC 0.38-12.5 μg/ml). N-Unsubstituted 4-aminopyrazoles shown high radical-scavenging activity in ABTS test, ORAC/AAPH and oxidative erythrocyte hemolysis assays. 1-Methyl-5-phenyl-3-trifluoromethylpyrazol-4-aminium chloride revealed potential anticancer activity against HeLa cells (SI > 1351). The pronounced analgesic activity was found for 4-nitroso- and 4-aminopyrazoles having phenyl fragment at the position 5 in "hot plate" test. The most of the obtained pyrazoles had a moderate acute toxicity.

In vivo and in vitro evaluation of pharmacological activities of Adenia trilobata (Roxb.)

Adenia trilobata, locally known as akandaphal in Bangladesh, has some traditional uses. Leaves and stems extracted with pure methanol (MEATL, MEATS) and fractioned by n-hexane (NFATL, NFATS), which was subjected to qualitative phytochemical analysis. The qualitative phytochemical analysis of four extracts showed the presence of secondary metabolites such as alkaloid, carbohydrate, glycosides, flavonoids, phenols, flavonol, and saponins. All four extracts of A. trilobata, exhibited a strong antioxidant activity while a moderately (MEATS = 328 μg/mL) to weakly toxic (NFATL = 616.85 μg/mL) LC₅₀ observed in brine shrimp lethality bioassay. In thrombolytic test, MEATL (18.54 ± 2.18%; P < 0.01) and MEATS (25.58 ± 4.76%; P < 0.0001) showed significant percentage of clot lysis in human blood. The in vivo analgesic activity carried by acetic acid test and formalin test, while the antidiarrheal activity assayed by two standard methods e.g., castor oil-induced diarrhea and castor oil-induced gastrointestinal motility. Both, in vivo model, showed an extremely significant (P < 0.0001) dose-dependent manner percentage of inhibition in comparison to the control group. Present results suggested, A. trilobata could be a potential source for antioxidative, cytotoxic, thrombolytic, analgesic, antidiarrheal agents which require further study to identify the mechanism of A. trilobata.

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Detection of different plant metabolites in extracts of different plant parts.

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Strong antioxidant activity was found for all four extracts.

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Moderate to weakly toxic LC₅₀ observed in brine shrimp lethality bioassay.

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A significant percentage of clot lysis in human blood was perceived.

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Extremely significant analgesic and antidiarrheal activity was found.

Gas chromatography-mass spectrometry (GM-MS) analysis and biological activities of the aerial part of Cleome amblyocarpa Barr. and Murb

Cleome amblyocarpa Barr. and Murb is a medicinal plant widespread in North Africa and widely used in Tunisia to treat diabetes and colic. The non-volatile (polyphenols, flavonoids, tannins, and flavonols) and volatile compounds (GC-MS) of C. amblyocarpa leaves and stems have been studied. The antioxidant, antimicrobial, analgesic, and cytotoxic activities of hydroalcoholic extracts of C. amblyocarpa leaves and stems were also investigated. The major volatile components were β-caryophyllene (46.9%), eugenol (25.6%), ethyl 3-methylpentanoate (16.2%), 7-epi-silphiperfol-5-ene (11.0%), and α-copaene (7.0%). The antioxidant activity has been evaluated using various in vitro assays, such as DPPH free radical scavenging activity, iron-chelating capability, and ability to inhibit lipid peroxidation (TBARS). The antibacterial and antifungal effectiveness of leaves and stems parts of Cleome amblyocarpa were investigated by means of the disc diffusion and microdilution techniques. The in vitro cytotoxicity of the hydroalcoholic extract of C. amblyocarpa on A549 and H1299 lung adenocarcinoma cells was determined using the crystal violet assay. The acute toxicity of the extracts on Swiss albino mice at the doses of 3000, 1500, and 500 mg/kg body weight was evaluated. The analgesic effect of leaves and stems extract was also determined by means of the acetic acid induced writhing test. The results indicated that the leaves have higher phenols, and flavonoids contents and potential antioxidant, antimicrobial, and anticancer activities in comparison to stem. In addition, the aerial part of C. amblyocarpa did not cause signs of toxicity or death in animals at doses up to 3000 mg/kg and have a significant analgesic activity.

Grayanane diterpenoid glucosides as potent analgesics from Pieris japonica

A total of fifteen grayanane diterpenoid glucosides including eight undescribed ones, pierisjaponosides A-H, were isolated from the leaves of Pieris japonica (Thunb.) D. Don ex G. Don (Ericaceae). Their structures were established by extensive spectros copic techniques including HRESIMS and NMR, as well as chemical methods. The absolute configurations of pierisjaponosides A, B, and D were finally established by single-crystal X-ray diffraction with Cu Kα radiation. This is the first time to report the crystal structure of a 5,9-epoxygrayanane diterpenoid glucoside. Pierisjaponoside E represents the first example of a 9β-hydroxygrayan-1(10)-ene diterpenoid. All the isolated grayanane diterpenoid glucosides were evaluated for their analgesic activities in the acetic acid-induced writhing models in mice, and showed significant analgesic effects. Pierisjaponosides A and C-H, micranthanoside A, pieroside A, and craiobiosides A and B displayed significant analgesic effects with the writhe inhibition rates over 50% at a dose of 5.0 mg/kg. Pierisjaponoside E exhibited significant analgesic activities with the percentage inhibitions of 81.7%, 70.4%, and 52.1% at the doses of 5.0, 1.0, and 0.2 mg/kg, respectively. The preliminary structure-activity relationships of grayanane diterpenoid glucosides as potent analgesics were discussed, giving some clues to design novel analgesics.

Expression, Purification and Docking Studies on IMe-AGAP, the First Antitumor-analgesic Like Peptide from Iranian Scorpion Mesobuthus eupeus

Scorpion venom contains different toxins with multiple biological functions. IMe-AGAP is the first Analgesic-Antitumor like Peptide (AGAP) isolated from Iranian scorpion Mesobuthus eupeus. This peptide is similar to AGAP toxin with high analgesic activity, extracted from Chinese scorpion and inhibits NaV1.8 and NaV1.9 voltage-gated sodium channels involved in the pain pathway. In this study, IMe-AGAP was cloned in a prokaryotic expression vector; expression of toxin in Escherichia coli (E. coli) was assayed and then purified. In in-silico studies, peptide sequence was compared with other scorpion analgesic toxins. The structures of IMe-AGAP and sodium channels were modeled using homology modeling. Structural evaluation and stereo-chemical analysis of modeled structures were performed using RAMPAGE web server Ramachandran plots. Hex Server was used to investigate the interactions between IMe-AGAP and S3-S4 and also S5-S6 segments of NaV1.8 and NaV1.9. Binding energies calculation was used for evaluation of protein docking. Soluble expression of IMe-AGAP in bacteria was investigated by SDS-PAGE analysis. Pure recombinant protein was obtained by Ni-NTA affinity chromatography. The results of three-dimensional structure prediction showed βαββ topology for the toxin that is similar to the conserved structure of α-toxins. Comparison analysis between IMe-AGAP and AGAP toxins exhibited high similarity in homology modeling. Docking analysis demonstrated that IMe-AGAP can interact with NaV1.8 and NaV1.9 domains involved in pain. According to the results of homology studies and docking, IMe-AGAP might be a novel potential drug for pain treatment.

Analgesic, Anti-inflammatory and In-vitro Hyaluronidase Inhibitory Properties of the Leaf Extract and Solvent Fractions of Otostegia Fruticosa (Forssk.) Schweinf. ex Penzig

Otostegia fruticosa is traditionally used to treat tonsillitis, stomach ache, asthma, arthritis, and febrile illness in different parts of Ethiopia and other countries. In this experiment 70% ethanolic crude extract and fractions of the leaf of Otostegia fruticosa (Forssk.) Schweinf. ex Penzig were evaluated for their in-vivo anti-inflammatory and analgesic activities and in-vitro hyaluronidase inhibition properties at different concentrations. Tail immersion, acetic acid induced writhing and carrageenan-induced paw edema model were used to assess the in-vivo analgesic and anti-inflammatory activities, respectively. Swiss albino mice of either sex were randomly divided into five groups of six mice per group and for evaluation of the fractions randomly divided into six groups of six mice per group. The test groups were treated with hydroalcoholic extract of Otostegia fruticosa (O. fruticosa) at doses of 100, 200, and 400 mg/kg. The positive control groups received either pethidine 5 mg/kg or aspirin at 100 mg/kg or 150 mg/kg. The negative control groups were orally given sunflower oil. All the fractions were administered at the dose of 400 mg/kg. In all models, the higher dose (400 mg/kg) of the crude extract and chloroform fraction showed a significant central and peripheral analgesic and anti-inflammatory activities with comparable effects to standards used. The hyaluronidase inhibition assay result showed that the test samples displayed concentration-dependent inhibitory activities. These findings indicate that 70% ethanol extract and organic solvent fractions of O. fruticosa leaves have potential analgesic, anti-inflammatory, and enzyme inhibitory activities.

Analgesic diterpenoids with diverse carbon skeletons from the leaves of Rhododendron auriculatum

Sixteen diterpenoids including nine undescribed ones, named rhodoauriculatols A-I, were isolated from the leaves of Rhododendron auriculatum Hemsl. Sixteen diterpenoids belong to seven diverse carbon skeletons, which were classified into 1,10-seco-grayanane, 1,10:2,3-diseco-grayanane, A-homo-B-nor-ent-kaurane, ent-kaurane, 4,5-seco-ent-kaurane, leucothane, and grayanane, respectively. Their structures were determined by the detailed HRESIMS, 1D and 2D NMR, UV, and IR data analysis, and their absolute configurations were established by single crystal X-ray diffraction analysis, electronic circular dichroism (ECD) data analysis, ECD calculation, as well as chemical methods. Rhodoauriculatols A-C possess a rare 1,10-seco-grayanane diterpene skeleton. Rhodoauriculatol D is the second example of the 1,10:2,3-diseco-grayanane diterpenoids, and rhodoauriculatol E is the fourth example of the A-homo-B-nor-ent-kaurane diterpenoids. Rhodomicranone E was reported as a natural product for the first time. All the isolated sixteen diterpenoids showed analgesic activities in the acetic acid-induced writhing test. Rhodoauriculatols B, E-G, rhodomicranone E, pierisformoside F, and micranthanoside A showed significant analgesic activities with the inhibition rates over 40%, and their preliminary structures-activity relationships were studied.

Seven new veratramine-type alkaloids with potent analgesic effect from Veratrum taliense

ETHNOPHARMACOLOGICAL RELEVANCE

Veratrum taliense is traditionally used TCMs in Yunnan province of China for pain and inflammation. Previous research and clinical applications have shown that V. taliense had significant analgesic activity. Jevine-type alkaloids were shown to be one of the anti-inflammatory and analgesic agents from V. taliense. However, other types of compounds from V. taliense related to its traditional use remains unknown.

AIM OF THE STUDY

To identify veratramine-type steroidal alkaloids with analgesic effects from the roots and rhizomes of V. taliense.

MATERIALS AND METHODS

Compounds were isolated from the roots and rhizomes of V. taliense by chromatographic separation. Their structures were elucidated based on UV, IR, NMR and MS spectra data. Analgesic activity was assessed with acetic acid-induced writhing in mice model.

RESULTS

Seven new veratramine-type alkaloids were isolated from the roots and rhizomes of V. taliense. They all exhibited significant analgesic activity, of which alkaloids 1 and 4 were more potent antalgic than the well-known analgesic drug, pethidine.

CONCLUSIONS

The veratramine-type alkaloids from V. taliense may serve as new leads for the discovery of analgesic drugs.

Evaluation of α-amylase, lipase inhibition and in-vivo pharmacological activities of Eucalyptus camaladulensis Dehnh leaf extract

In this present study, phytochemical screening, anti-ulcer assay, anti-diarrhea assay, anti-inflammatory assay, analgesic assay, lipase activity assay, amylase activity assay and the anti-bacterial activity of Eucalyptus camaladulensis Dehnh leaf extracted with methanol and 50% ethanol was analyzed for biological significance. Physical characterization of the non-volatile component revealed the higher yield of 16.92% in 50% ethanol expediting the use of 50% ethanol as a better alternative. Further use of crude extract revealed 33.89% (IC₅₀ = 1.44 mg/ml) of α-amylase inhibition by methanol extract and 33.87% (IC₅₀ = 3.21 mg/ml) lipase inhibition by 50% ethanol extract. Furthermore, 44.44% protective ratio towards ulcer was observed with the methanol extract, whereas 54.58% anti-inflammatory activity was shown by the 50% ethanol extract. The effectiveness of the extract was further enhanced by the presence of 62.54% motility and best analgesic property at 180 min of the exposure of the extract orally. The antioxidant activity of crude methanol extract revealed an IC₅₀ value 601.8 μg/ml whereas, ethanol extract showed 1279.58 μg/ml in DPPH assay. Result revealed several health benefits of E. camaldulensis Dehnh leaf.

Investigation of the anti-inflammatory and the analgesic effects of the extracts from Smilax ornata Lem. (Jamaican sarsaparilla) plant

ETHNOPHARMACOLOGICAL RELEVANCE

Smilax ornata Lem. is used in folklore medicine to treat rheumatoid arthritis and rheumatic pain. This particular claim has never been scientifically validated before in this plant species and hence, it forms the reason for this investigation.

OBJECTIVE

To investigate whether the methanol and ethyl acetate extracts of Smilax ornata Lem. possess anti-inflammatory and analgesic properties in Sprague-Dawley rats.

METHODS

The anti-inflammatory and analgesic activities were investigated using carrageenan-induced paw oedema model and the tail-flick model respectively.

RESULTS

The methanol extracts (200 and 400 mg/kg) and the ethyl acetate extract (400 mg/kg) exhibited significant (P < 0.05) anti-inflammatory activity when compared with that of their control groups (saline and vegetable oil respectively), with an onset of 150 min and a duration of 2.5 h. The methanol extract (200 mg/kg) exhibited significant (P < 0.05) analgesic activity, with an onset of 60 min and a duration of 2 h. Also, the methanol and the ethyl acetate extracts (400 mg/kg) exhibited significant (P < 0.05) analgesic activity when compared with that of their control groups (saline and vegetable oil respectively), with an onset of 30 min and a duration of 2.5 h.

CONCLUSION

The present study provided scientific justification that the extracts of Smilax ornata Lem. possess significant anti-inflammatory and analgesic activities.

Cyclic enaminone as new chemotype for selective cyclooxygenase-2 inhibitory, anti-inflammatory, and analgesic activities

The cyclic enaminone moiety has been identified as a new scaffold for selective inhibition of cyclooxygenase-2 with anti-inflammatory and analgesic activities. The designed cyclic enaminones have been synthesized conveniently through the development of a new catalyst-free methodology and evaluated for cyclooxygenase (COX-1 and COX-2) inhibitory activities. Three compounds 7d, 8, and 9 predominantly inhibited COX-2 with selectivity index of 74.09, 19.45 and 108.68, respectively, and were assessed for in vivo anti-inflammatory activity in carrageenan induced rat paw edema assay. The anti-inflammatory activity of 7d was comparable to that of celecoxib at a dose of 12.5 mg/kg. However, the compounds 8 and 9 were more/equally effective as anti-inflammatory agent compared to celecoxib at the doses of 12.5 mg/kg and 25 mg/kg and also exhibited anti-inflammatory activity comparable to that of diclofenac. The therapeutic potential of the most active compound 9 was further assessed by performing in vivo thermal and mechanical hyperalgesia tests using various models that revealed its analgesic activity. The in vivo non-ulcerogenicity of 9 revealed the gastrointestinal safety as compared to the non-selective COX inhibitor indomethacin. The in vitro antioxidant activity and in vivo experiments on heart rate and blood pressure provided the cardiovascular safety profile of 9. The molecular docking studies rationalize the COX-2 selectivity of the newly found anti-inflammatory compounds 7d, 8, and 9.

Synthesis and anti-nociceptive potential of isoxazole carboxamide derivatives

Background

Isoxazole is an important pharmacophore in medicinal chemistry with a wide range of pharmacological activities. The present study deals with the synthesis and evaluation of antinociceptive potential of nine novel 3-substituted-isoxazole-4-carboxamide derivatives.

Synthesis

In the first step, respective oxime was prepared and further treated with ethylacetoacetate and anhydrous zinc chloride followed by hydrolysis of ester to furnish 3-substituted isoxazole-4-carboxylic acid. The respective carboxylic acids were converted to acid chlorides and condensed with aromatic amines to get the target carboxamide derivatives (A1–A5 and B1–B5). These compounds were characterized by FTIR, ¹HNMR, ¹³CNMR and elemental analysis data and screened for their analgesic activity using acetic acid-induced writhing assay and hot plat test in mice and compared with the standard centrally acting analgesic, tramadol.

Results

All the synthesized carboxamide derivatives showed low to moderate analgesic activity. Among the synthesized derivatives B2 having methoxy (OCH₃) showed high analgesic activity as compared to tramadol both in acetic acid-induced writhing assay and hot plate assay at dose of 6 mg/kg. To examine the involvement of opioidergic mechanism in the mediation of analgesic effects of isoxazole derivatives animals were further treated with non-selective opioid analgesic, naloxone (0.5 mg/kg). The results showed that compounds A3 and B2 follow a non-opioid receptor pathway in the mediation of analgesic effects. Synthesized compounds A3 and B2 were docked against non-opioid receptors COX-1 (3N8X), COX-2 (1PXX) and human capsaicin receptor (HCR, 3J9J) to analyze their binding interactions. They showed binding energies in the range of − 7.5 to − 9.7 kcal/mol.

Conclusions

The results indicated that isoxazole carboxamide derivatives possess moderate analgesic potential especially compounds A3 and B2 can be considered as lead molecules and explored further for pain management with fewer side effects.

Synthesis and pharmacological evaluation of novel arylpiperazine oxicams derivatives as potent analgesics without ulcerogenicity

Gastrotoxicity continues to be a major issue in therapy with nonsteroidal anti-inflammatory drugs (NSAIDs). Medicine is yet to develop absolutely safe analgesics. Numerous strategies are employed to discover new, safer NSAIDs, for example selective inhibition of cyclooxygenase-2, new molecular targets (e.g. microsomal prostaglandin E₂ synthase-1), incorporation of cytoprotective compounds in the drug molecule or modification of the classic NSAIDs currently available on the market. The research presented in this paper is indicative of a current worldwide trend in this area of science, and is an example of the fourth strategy noted above. Two series of new arylpiperazine derivatives of the classic NSAID - piroxicam, were developed by conventional synthesis. The full range of compounds obtained proved to be between two and five times analgesically more potent than the reference drug and, most importantly, they did not show any ulcerogenic activity.

Discovery of NR2B-selective antagonists via scaffold hopping and pharmacokinetic profile optimization

Selective N-methyl-d-aspartate receptor subunit 2B (NR2B) antagonists show potential as analgesic drugs, and do not cause side effects associated with non-selective N-methyl-d-aspartate (NMDA) antagonists. Using a scaffold-hopping approach, we previously identified isoxazole derivative 4 as a potent selective NR2B antagonist. In this study, further scaffold hopping of isoxazole derivative 4 and optimization of its pharmacokinetic profile led to the discovery of the orally bioavailable compound 6v. In a rat study of analgesia, 6v demonstrated analgesic effects against neuropathic pain.

Rhodomicranosides A-I, analgesic diterpene glucosides with diverse carbon skeletons from Rhododendron micranthum

Nine previously undescribed diterpene glucosides, rhodomicranosides A-I, comprising leucothane, 4,5-seco-ent-kaurane, and grayanane types, respectively, were isolated from the leaves of Rhododendron micranthum, along with seven known diterpenoids. Their structures were elucidated based on extensive spectroscopic analyses such as HRESIMS, 1D and 2D NMR, UV, and IR, and their absolute configurations were determined by various methods including X-ray diffraction analysis, electronic circular dichroism spectroscopy (ECD), calculated ECD, and Mo₂(OAc)₄-induced ECD, as well as chemical methods. This is the first time to report the crystal structures of leucothane diterpene glycosides. Rhodomicranosides A-C represent the first examples of 15α-hydroxy-leucothane diterpenoids, leucothane diterpene diglucosides, and 9β-hydroxy-leucothane diterpenoids, respectively. Rhodomicranosides D and E are the second and third examples of 4,5-seco-ent-kaurane diterpenoids, and this is the first time to report 4,5-seco-ent-kaurane-type diterpenoids from the genus of Rhododendron. Rhodomicranosides F and G are the first examples of 5α-H-grayan-1(10),9(11)-diene-6-one diterpenoids. Some isolated diterpenoids were evaluated for their analgesic activity in an acetic acid-induced writhing test, and rhodomicranosides A-E and H, pierisformoside F, iso-grayanotoxin II, and grayanotoxins I, III, and IV showed significant analgesic effects with the percentage inhibitions over 50% at the dose of 1.0 mg/kg. In particular, grayanotoxins I and III exhibited more potent analgesic activity than morphine at a dose of 0.2 mg/kg, and they showed significant analgesic activity even at a lower dose of 0.04 mg/kg with the inhibition rates of 71.5% and 69.3%, respectively. Their preliminary structure-activity relationships were discussed.