Analgesic effects of cuminic alcohol (4-isopropylbenzyl alcohol), a monocyclic terpenoid, in animal models of nociceptive and neuropathic pain: Role of opioid receptors, L-arginine/NO/cGMP pathway, and inflammatory cytokines

Anti-Inflammatory, Antihyperalgesic, and Gastric Safety Profiling of Ocimene: Attenuation of Nonsteroidal Anti-Inflammatory Drug-Induced Gastric Ulcers by Modulating Toll-like Receptor 4 and Pyroptosis Pathways

Monocyclic monoterpenoid ocimene (OC) was evaluated as a potential inhibitor of TLR4/NLRP3/GSDMD-driven pyroptosis, implicated in conditions such as chronic pain, inflammation, and gastric ulcers. This study investigated OC's protective effects against indomethacin (IND)-induced gastric ulcers, aiming to identify an analgesic and anti-inflammatory agent with enhanced gastric safety. OC's analgesic efficacy was demonstrated by reducing formalin-evoked paw licking, writhing provoked by acetic acid-induced and tail immersion reaction latencies in animal models. Anti-inflammatory effects were confirmed through reduced paw edema (formalin and carrageenan), along with in vitro suppression of protein denaturation and membrane stabilization. qRT-PCR showed that OC significantly (p < 0.001) downregulated TLR4, MyD88, NFκB, NLRP3, and inflammatory mediators (IL-18, IL-1β, caspase-1, ASC, GSDMD, COX-1, COX-2) with upregulation of anti-inflammatory cytokines IL-4 and IL-10. ELISA results indicated a reduction in the oxidative stress marker MDA and inflammatory mediators PGE-2 and 5-LOX, with increased antioxidant markers GSH, CAT, and SOD. Macroscopic and histological analysis showed that OC provided gastric protection by reducing the ulcer index (UI) and improving ulcer scores, with effects comparable to omeprazole. In summary, OC shows potential as a safe antinociceptive and anti-inflammatory agent, effectively reducing gastric ulcer risk by mitigating pyroptosis and inflammation, critical for treating chronic inflammatory conditions with hyperalgesia.

Role of l -arginine/nitric oxide/cyclic GMP/K ATP channel signaling pathway and opioid receptors in the antinociceptive effect of rutin in mice

The l -arginine ( l -Arg)/nitric oxide/cyclic GMP/potassium channel (K ATP ) pathway and opioid receptors are known to play critical roles in pain perception and the antinociceptive effects of various compounds. While there is evidence suggesting that the analgesic effects of rutin may involve nitric oxide modulation, the direct link between rutin and the l -Arg/nitric oxide/cyclic GMP/K ATP pathway in the context of pain modulation requires further investigation. The antinociceptive effect of rutin was studied in male NMRI mice using the formalin test. To investigate the role of the l -Arg/nitric oxide/cyclic GMP/K ATP pathway and opioid receptors, the mice were pretreated intraperitoneally with different substances. These substances included l -Arg (a precursor of nitric oxide), S-nitroso- N -acetylpenicillamine (SNAP, a nitric oxide donor), N(gamma)-nitro- l -arginine methyl ester (L-NAME, an inhibitor of nitric oxide synthase), sildenafil (an inhibitor of phosphodiesterase enzyme), glibenclamide (a K ATP channel blocker), and naloxone (an opioid receptor antagonist). All pretreatments were administered 20 min before the administration of the most effective dose of rutin. Based on our investigation, it was found that rutin exhibited a dose-dependent antinociceptive effect. The administration of SNAP enhanced the analgesic effects of rutin during both the initial and secondary phases. Moreover, L-NAME, naloxone, and glibenclamide reduced the analgesic effects of rutin in both the primary and secondary phases. In conclusion, rutin holds significant value as a flavonoid with analgesic properties, and its analgesic effect is directly mediated through the nitric oxide/cyclic GMP/K ATP channel pathway.

Antinociceptive effect of Nephelium lappaceum L. fruit peel and the participation of nitric oxide, opioid receptors, and ATP-sensitive potassium channels

Introduction: Nephelium lappaceum L. (Sapindaceae) is a plant known as rambutan. It is used for various purposes in traditional medicine. Objective: We aimed to evaluate the antinociceptive effects of the ethanol extract of the fruit peel of N. lappaceum (EENL), the mechanisms involved in these effects, and the acute toxicity in zebrafish. Methods: We performed chromatography coupled to mass spectrometry, acute toxicity assay in zebrafish, and evaluation in mice submitted to models of nociception and locomotor activity. Results: We identified (epi)-catechin, procyanidin B, and ellagic acid and its derivatives in EENL. We did not find any toxicity in zebrafish embryos incubated with EENL. The locomotor activity of mice submitted to oral pretreatment with EENL was not changed, but it reduced the abdominal constrictions induced by acetic acid, the licking/biting time in both the first and second phase of formalin testing and capsaicin testing, and carrageenan-induced paw mechanical allodynia. Oral pretreatment with EENL increased latency time in the hot plate test. This antinociceptive effect was significantly reversed by naloxone, L-arginine, and glibenclamide respectively showing the participation of opioid receptors, nitric oxide, and KATP channels as mediators of EENL-induced antinociception. Conclusion: EENL causes antinociception with the participation of opioid receptors, nitric oxide, and KATP channels, and is not toxic to zebrafish.

Therapeutic Potential of Myrtenal and Its Derivatives-A Review

The investigation of monoterpenes as natural products has gained significant attention in the search for new pharmacological agents due to their ability to exhibit a wide range in biological activities, including antifungal, antibacterial, antioxidant, anticancer, antispasmodic, hypotensive, and vasodilating properties. In vitro and in vivo studies reveal their antidepressant, anxiolytic, and memory-enhancing effects in experimental dementia and Parkinson's disease. Chemical modification of natural substances by conjugation with various synthetic components is a modern method of obtaining new biologically active compounds. The discovery of new potential drugs among monoterpene derivatives is a progressive avenue within experimental pharmacology, offering a promising approach for the therapy of diverse pathological conditions. Biologically active substances such as monoterpenes, for example, borneol, camphor, geraniol, pinene, and thymol, are used to synthesize compounds with analgesic, anti-inflammatory, anticonvulsive, antidepressant, anti-Alzheimer's, antiparkinsonian, antiviral and antibacterial (antituberculosis) properties. Myrtenal is a perspective monoterpenoid with therapeutic potential in various fields of medicine. Its chemical modifications often lead to new or more pronounced biological effects. As an example, the conjugation of myrtenal with the established pharmacophore adamantane enables the augmentation of several of its pivotal properties. Myrtenal-adamantane derivatives exhibited a variety of beneficial characteristics, such as antimicrobial, antifungal, antiviral, anticancer, anxiolytic, and neuroprotective properties, which are worth examining in more detail and at length.

Antinociceptive Effect of a p-Cymene/β-Cyclodextrin Inclusion Complex in a Murine Cancer Pain Model: Characterization Aided through a Docking Study

Pain is one of the most prevalent and difficult to manage symptoms in cancer patients, and conventional drugs present a range of adverse reactions. The development of β-cyclodextrins (β-CD) complexes has been used to avoid physicochemical and pharmacological limitations due to the lipophilicity of compounds such as p-Cymene (PC), a monoterpene with antinociceptive effects. Our aim was to obtain, characterize, and measure the effect of the complex of p-cymene and β-cyclodextrin (PC/β-CD) in a cancer pain model. Initially, molecular docking was performed to predict the viability of complex formation. Afterward, PC/β-CD was obtained by slurry complexation, characterized by HPLC and NMR. Finally, PC/β-CD was tested in a Sarcoma 180 (S180)-induced pain model. Molecular docking indicated that the occurrence of interaction between PC and β-CD is favorable. PC/β-CD showed complexation efficiency of 82.61%, and NMR demonstrated PC complexation in the β-CD cavity. In the S180 cancer pain model, PC/β-CD significantly reduced the mechanical hyperalgesia, spontaneous nociception, and nociception induced by non-noxious palpation at the doses tested (p < 0.05) when compared to vehicle differently from free PC (p > 0.05). Therefore, the complexation of PC in β-CD was shown to improve the pharmacological effect of the drug as well as reducing the required dose.

Flavonoids and fractions from Saccharum officinarum L. juice: antinociceptive agents and molecular docking evaluations with µ-opioid receptor

Opioid receptors mediate antinociceptive effects. Methanolic fractions from sugarcane varieties (MFSCf) were evaluated in classic nociception models. Interactions between bioactive compounds and the µ-opioid receptor (µOR) through docking analysis were also studied. Five methanolic fractions of sugarcane juice were obtained and analysed by LC-ESI-MS/MS. The fractions and standards of phenolic compounds were evaluated in a nociception model using the formalin test. All MFSCfs exhibited antinociceptive activity in the first phase of the formalin test. Docking analyses corroborates with the in vivo test results, suggesting that the phenolic substances are able to activate µOR. These results, for the first time, implicate phenolic constituents from sugarcane juice and other phenolic compounds in the activation of µOR. The antinociceptive activity of fractions from sugarcane juice suggests the potential pharmacological use of this species, widely cultivated in Brazil.

3D-QSAR, ADME-Tox In Silico Prediction and Molecular Docking Studies for Modeling the Analgesic Activity against Neuropathic Pain of Novel NR2B-Selective NMDA Receptor Antagonists

A new class of selective antagonists of the N-Methyl-D-Aspartate (NMDA) receptor subunit 2B have been developed using molecular modeling techniques. The three-dimensional quantitative structure–activity relationship (3D-QSAR) study, based on comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) models, indicate that steric, electrostatic and hydrogen bond acceptor fields have a key function in the analgesic activity against neuropathic pain. The predictive accuracy of the developed CoMFA model (Q2 = 0.540, R2 = 0.980, R2 pred = 0.613) and the best CoMSIA model (Q2 = 0.665, R2 = 0.916, R2 pred = 0.701) has been successfully examined through external and internal validation. Based on ADMET in silico properties, L1, L2 and L3 ligands are non-toxic inhibitors of 1A2, 2C19 and 2C9 cytochromes, predicted to passively cross the blood–brain barrier (BBB) and have the highest probability to penetrate the central nervous system (CNS). Molecular docking results indicate that the active ligands (L1, L2 and L3) interact specifically with Phe176, Glu235, Glu236, Gln110, Asp136 and Glu178 amino acids of the transport protein encoded as 3QEL. Therefore, they could be used as analgesic drugs for the treatment of neuropathic pain.