Chromones from the endophytic fungus Bipolaris eleusines

Eight previously undescribed chromones eleusineketones A-H (1-8), as well as eight known compounds (9-16), were isolated from the endophytic fungus Bipolaris eleusines. These planar structures were created using an in-depth analysis of their spectral data, which included 1D, 2D, and HRESIMS data. Furthermore, the absolute configurations of compounds 1, 2, and 6 were determined by spectroscopic analysis and quantum chemical computational approaches, and compound 5 was determined by single-crystal X-ray diffraction analysis. The cytotoxic activity assay revealed that compounds 1 and 5 both inhibited MDA-MB-231 cells with IC50 values of 14.48 μM and 17.99 μM, respectively.

Synthesis, molecular docking studies and biological evaluation of N-(4-oxo-2-(trifluoromethyl)-4H-chromen-7-yl) benzamides as potential antioxidant, and anticancer agents

A series of novel chromone derivatives of (N-(4-oxo-2-(trifluoromethyl)-4H-chromen-6-yl) benzamides) were synthesized by treating 7-amino-2-(trifluoromethyl)-4H-chromen-4-one with K2CO3 and/or NaH, suitable alkyl halides and acetonitrile and/or 1,4-dioxane. The obtained products are in high yields (87 to 96%) with various substituents in short reaction times with no more by-products and confirmed by FT-IR, 1H, and 13C-NMR Spectral data. The in vitro cytotoxic activity was examined against two human cancer cell lines, namely the human lung adenocarcinoma (A-549) and the human breast (MCF-7) cancer cell line. Compound 4h showed promising cytotoxicity against both cell lines with IC50 values of 22.09 and 6.40 ± 0.26 µg/mL respectively, compared to that of the standard drug. We also performed the in vitro antioxidant activity by DPPH radical, hydrogen peroxide, NO scavenging, and total antioxidant capacity (TAC) assay methods, and they showed significant activities. The possible binding interactions of all the synthesized chromone derivatives are also investigated against selective pharmacological targets of human beings, such as HERA protein for cytotoxic activity and Peroxiredoxins (3MNG) for antioxidant activity which showed closer binding free energies than the standard drugs and evidencing the above two types of activities.

Open tubular capillary electrochromatography with dual-responsive polymer as coating for separation of chromones

Fabricating polymeric coatings that are responsive to multiple/dual stimuli is crucial and remains a major challenge in the development of highly efficient open tubular capillary electrochromatography (OT-CEC). In this study, a pH and temperature-responsive block copolymer, poly(styrene-maleic anhydride 2-dimethylamino ethyl methacrylate), P(St-MAn-DMAEMA), was designed and synthesized. Using P(St-MAn-DMAEMA) as the coating, an OT-CEC protocol was constructed for the analysis of chromones. The morphology and hydrophobicity-hydrophilicity of the polymeric coating could change via varying the environmental conditions, affecting the separation efficiency of OT-CEC. Interestingly, the best performance of OT-CEC was achieved at pH 9.7 and 45 °C via tuning the interactions between the coating and the analytes. Additionally, the proposed OT-CEC method exhibited a good linear range for the detection of the three test chromones from 10.0 to 100.0 μM, with all correlation coefficients (R2) >0.997. The coatings also had good stability and reusability. This work provides an approach for the preparation of new multiple-stimuli-responsive polymeric coatings for the establishment of OT-CEC systems.

Discovery of potent chromone-based autotaxin inhibitors inspired by cannabinoids

Autotaxin (ATX) is an enzyme primarily known for the production of lysophosphatidic acid. Being involved in the development of major human diseases, such as cancer and neurodegenerative diseases, the enzyme has been featured in multiple studies as a pharmacological target. We previously found that the cannabinoid tetrahydrocannabinol (THC) could bind and act as an excellent inhibitor of ATX. This study aims to use the cannabinoid scaffold as a starting point to find cannabinoid-unrelated ATX inhibitors, following a funnel down approach in which large chemical libraries sharing chemical similarities with THC were screened to identify lead scaffold types for optimization. This approach allowed us to identify compounds bearing chromone and indole scaffolds as promising ATX inhibitors. Further optimization led to MEY-003, which is characterized by the direct linkage of an N-pentyl indole to the 5,7-dihydroxychromone moiety. This molecule has potent inhibitory activity towards ATX-β and ATX-ɣ as evidenced by enzymatic studies and its mode of action was rationalized by structural biology studies using macromolecular X-ray crystallography.

Antimicrobial and antibiofilm activities of chromone derivatives against uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is a urinary tract pathogen responsible for most nosocomial urinary tract infections and can cause severe conditions like acute cystitis of the bladder or pyelonephritis. UPEC harbors a host of virulence factors like curli, hemolysin, siderophore, and motility factors and can form biofilm-like communities and quiescent reservoirs that aid its survival. This study was performed to investigate the antibiofilm, antimicrobial, and antivirulence potentials of three chromone derivatives, namely, 6-bromo 3-formylchromone, 6-chloro 3-formylchromone, and 3-formyl 6-isopropylchromone. These chromones had MICs against UPEC of 20, 20, and 50 µg/ml, respectively, inhibited biofilm formation by 72-96% at 20 µg/ml, and inhibited UPEC-associated virulence factors, that is, hemolysis, motility, curli, siderophore production, indole production, quiescent colony formation, and cell surface hydrophobicity. Gene expression analysis indicated these three derivatives downregulated virulence genes associated with toxins, biofilm production, and stress regulation and suggested they might target two-component UvrY response regulator. 3D-QSAR analysis showed that substitutions at the third and sixth positions of the chromone scaffold favor antimicrobial activity against UPEC. Furthermore, ADME profiles and C. elegans cytotoxicity assays indicated that these chromone derivatives are potent, safe drug candidates.

The solute polarization and structural effects on the nonlinear optical response of based chromone molecules

The solute polarization due to solvent is a an electrostatic quantum effect that impacts diverse molecular properties, including the nonlinear optical response of a material. An iterative procedure that allows updating the solute charge distribution in the presence of the solvent is combined with a sequential Monte Carlo / Quantum Mechanics methodology and Density Functional Theory methods to evaluate the nonlinear optical (NLO) response using the hyper Rayleigh scattering (HRS) of a series of chromones recently identified in Chamaecrista diphylla, an herbaceous plant abundant throughout the Americas and used in folk medicine. From this study, it is determined that from gas to solvent environment, the systems acquire low refractive index (n) and an improvement of the first hyperpolarizability (βHRS), signaling potential NLO uses. It is shown that the octupolar contributions (β J =3) superate the dipolar ones (β J =1) and dominate the second-order optical response in both gas and liquid phases, which indicate nontrivial optical materials. Moreover, the solvent environment and structural changes in the periphery can tune significantly the dipolar/octupolar balance, showing a key to control the decoupling between these contributions.

Inhibitors of ABCG2-mediated multidrug resistance: Lead generation through computer-aided drug design

Human breast cancer resistance protein (BCRP), known also as ABCG2, plays a major role in multiple drug resistance (MDR) in tumor cells. Through this ABC transporter, cancer cells acquire the ability of resistance to structurally and functionally unrelated anticancer drugs. Nowadays, the design of ABCG2 inhibitors as potential agents to enhance the chemotherapy efficacy is an interesting strategy. In this context, we have used computer-aided drug design (CADD) based on available data of a large series of potent inhibitors from our groups as an approach in guiding the design of effective ABCG2 inhibitors. We report therein the results on the use of the FLAPpharm method to elucidate the pharmacophoric features of one of the ABCG2 binding sites involved in the regulation of the basal ATPase activity of the transporter. The predictivity of the model was evaluated by testing three predicted compounds which were found to induce high inhibitory activity of BCRP, in the nanomolar range for the best of them.

Copper(II) and oxidovanadium(IV) complexes of chromone Schiff bases as potential anticancer agents

We report the synthesis, characterization and biological screening of new chromone Schiff bases derived from the condensation of three 6-substituted-3-formyl-chromones with pyridoxal (HL^1-3) and its Cu(II) complexes [Cu(L^1-3)Cl], 1-3. For the 6-methyl derivative, HL², the V^IVO-complex [VO(L²)Cl] (5), as well as ternary Cu and V^IVO complexes with 1,10-phenanthroline (phen), [Cu(L²)(phen)Cl] (4) and [VO(L²)(phen)Cl] (6), were also prepared and evaluated. Their stability in aqueous medium and radical scavenging activity toward DPPH are screened, with [Cu(L²)(phen)Cl] (4) showing hydrolytic stability and [VO(L²)(phen)Cl] (6) high radical scavenging activity. Spectroscopic studies establish bovine serum albumin (BSA), a model for HSA, as a potential reversible carrier of [Cu(L²)(phen)Cl] in blood with K_BC ≈ 10⁵ M^-1. The cytotoxic activity of a group of compounds is evaluated against a panel of human cancer cell lines of different origin (ovary, cervix, brain and breast) and compared to normal cells. Our results indicate that Cu complexes are more cytotoxic than the ligands but not selective towards cancer cells. The most potent complexes (4 and 6) are further evaluated for their apoptotic potential, induction of reactive oxygen species (ROS) and genotoxicity. Both complexes efficiently triggered cell death through apoptosis as evaluated by DNA morphology and TUNEL assay, increased ROS formation as determined by DCFDA (2',7'-dichlorodihydrofluorescein diacetate) analysis, and induced genotoxic damage as visualized via COMET assay in all cancer cells under study. Therefore, 4 and 6 may be potential precursor anticancer molecules, yet they need to be targeted toward cancer cells.

Chromone a Privileged Scaffold in Drug Discovery: Developments on the Synthesis and Bioactivity

Chromones are the class of secondary metabolites broadly occurred in the plant kingdom in a noticeable quantity. This rigid bicyclic system has been categorized "as privileged scaffolds in compounds" in medicinal chemistry. The wide biological responses made them an important moiety in a drug discovery program. This review provides updates on the various methods of synthesis of chromones and biological applications in medicinal chemistry. Various synthetic strategies for the construction of chromones include readily available phenols, salicylic acid and its derivatives, ynones, chalcones, enaminones, chalcones and 2-hydroxyarylalkylketones as starting materials. Synthesis of chromones by using metal, metal free, nanomaterials and different catalysts are included. Details of diverse biological activities such as anti-cancer agents, antimicrobial agents, anti-viral property, anti-inflammatory agents, antioxidants, Monoamine Oxidase-B (MAO-B) Inhibitors, anti-Alzheimer's agents, anti-diabetic agent, antihistaminic potential, antiplatelet agents of chromone derivatives are diecussed.

Spororrminone A and 2-epi-spororrminone A, two new chromones from an endolichenic fungus Sporormiella irregularis

Two new chromones, spororrminone A (1, (S)-5-hydroxy-2-methyl-4-oxo-2-((S)-5-oxotetrahydrofuran-2-yl)chroman-7-carboxylic acid) and 2-epi-spororrminone A (2, (R)-5-hydroxy-2-methyl-4-oxo-2-((S)-5-oxotetrahydrofuran-2-yl)chroman-7-carboxylic acid), were isolated from an EtOAc extract of an endolichenic fungal strain Sporormiella irregularis (No. 71-11-4-1). The structures of these compounds were identified by spectroscopic analyses. The absolute configuration of 1 was established by single-crystal X-ray diffraction. Spororrminone A (1) and 2-epi-spororrminone A (2) represent the first examples of 2-(5-oxotetrahydrofuran-2-yl) chromones with 7-carboxylic group.

Antinociceptive effects of intrathecal cimifugin treatment: a preliminary rat study based on formalin test

Background

Cimifugin is one of the components of the root of Saposhnikovia divaricata. The extract derived from S. divaricata is traditionally used as an analgesic. This study was conducted to evaluate the analgesic effect of intrathecal cimifugin in the formalin test.

Methods

Male Sprague–Dawley rats (n = 20) were randomized into four groups for intrathecal administration of 70% dimethylsulfoxide and various doses of cimifugin (100 μg, 300 μg, and 1,000 μg). The typical flinch response after the injection of 5% formalin into the hind paw was assessed in two distinct phases: phase 1 until 10 min, and phase 2 from 10 min to 60 min. ED₅₀ values were calculated via linear regression.

Results

Intrathecal cimifugin significantly reduced the flinch response in both phases of the formalin test. Significant antinociceptive effects of cimifugin were found with the dose of 300 μg in phase 1 and the dose of 100 μg in phase 2. The ED₅₀ value (95% confidence intervals) of intrathecal cimifugin was 696.1 (360.8–1,342.8) μg during phase 1 and 1,242.8 (42.0–48,292.5) μg during phase 2.

Conclusions

Intrathecal cimifugin has an antinociceptive effect against formalin-induced pain. Cimifugin has an anti-inflammatory effect at low concentrations, and non-inflammatory analgesic effect at higher concentrations.

Chromones and coumarins from Saposhnikovia divaricata (Turcz.) Schischk. Growing in Buryatia and Mongolia and their cytotoxicity

ETHNOPHARMACOLOGICAL RELEVANCE

Saposhnikovia divaricata (family Apiaceae) a traditional medicinal plant distributed in many provinces of China, is well known for the pharmaceutical value and has been used for rheumatic arthritis, and anxiety in children. Antiviral, antioxidant and antiproliferative activities were also mentioned. The application of this plant are recorded in the Chinese Medicine (CM) classical text the Shen Nong's Materia Medica (Shen Nong Ben Cao Jing). In this monograph S. divaricata (syn Radix Ledebouriella divaricata) is graded as a premium-grade herb, with their broad-spectrum of therapeutic applications for the treatment of cough, common cold, arthralgia, as well as in rheumatic disorders.

AIM OF THE STUDY

To isolate and identify chemical constituents (chromones and coumarins) from S. divaricata, collected in Buryatia and Mongolia and to study their in vitro anticancer activity against MEL-8, U-937, DU-145, MDA-MB-231 and ВТ-474 cell lines.

MATERIALS AND METHODS

An 40% aqueous ethanol extract of the roots of S. divaricata was prepared and further successively fractionated by extraction with petroleum ether, diethyl ether, tert-butyl methyl ether and ethyl acetate. The obtained extracts were subjected to a series of chromatographic separations on silica gel for isolation of individual compounds. Isolated compounds were tested for their cytotoxicity with respect to model cancer cell lines using the conventional MTT assays.

RESULTS

Total of 15 individual compounds: coumarins scopoletin 2, bergapten 3, isoimperatorin 4, marmesin 5, (+)-decursinol 9, (-)-praeruptorin B 10, oxypeucedanin hydrate 11, chromones: hamaudol 6, cimifugin 7, 5-О-methylvisamminol 8, chromone glycosides: prim-O-glucosylcimifugin 12, sec-O-glucosylhamaudol 13, 4'-O-β-D-glucopyranosyl-5-О-methylvisamminol 14, 4'-O-β-D-glucopyranosylvisamminol (15) and also polyyne compound panaxinol 1 were isolated and characterized. The structure of dihydropyranocoumarin 10 was confirmed by X-ray diffraction analyses. HPLC-UV method was used for determination of the content of most abundant chromones 7, 12 and 14 in the roots of S. divaricata, collected in Mongolia. Compounds 3-11 and 13, 14 were evaluated for their cytotoxicity with respect to model cancer cell lines. All the compounds were non-toxic in the hemolysis test.

CONCLUSION

This report about the phytochemical profiles of S. divaricata growing in Mongolia and Buryatia led to the identification of 14 compounds including coumarins and chromones. The available coumarins and chromones may serve as new leads for the discovery of anticancer drugs.

Chromones bearing amino acid residues: Easily accessible and potent inhibitors of the breast cancer resistance protein ABCG2

The Breast Cancer Resistance Protein (BCRP/ABCG2) belongs to the G class of ABC (ATP-Binding Cassette) proteins, which is known as one of the main transporters involved in the multidrug resistance (MDR) phenotype that confer resistance to anticancer drugs. The aim of this study was to design, synthesize and develop new potent and selective inhibitors of BCRP that can be used to abolish MDR and potentialize clinically used anticancer agents. In previous reports, we showed the importance of chromone scaffold and hydrophobicity for the inhibition of ABC transporters. In the present study we report the design and development of chromones linked to one or two amino acids residues that are either hydrophobic or found in the structure of FTC, one of most potent (but highly toxic) inhibitors of BCRP. Herewith, we report the synthesis and evaluation of 13 compounds. The studied molecules were found to be not toxic and showed strong inhibition activity as well as high selectivity toward BCRP. The highest activity was obtained with the chromone bearing a valine residue (9c) which showed an inhibition activity against BCRP of 50 nM. The rationalization of the inhibition potential of the most active derivatives was performed through docking studies. Taken together, the ease of synthesis and the biological profile of these compounds render them as promising candidates for further development in the field of anticancer therapy.

Evolution of chromone-like compounds as potential antileishmanial agents, through the 21st century

INTRODUCTION

Leishmaniasis is one of the most neglected diseases of modern times that mainly affects people from developing countries, with approximately 350 million people considered at risk of developing leishmaniasis. Therefore, the development of novel antileishmanial treatments is becoming the focus of numerous research groups, with the support of the World Health Organization, which hopes to eradicate this disease in the near future.

AREAS COVERED

This review focuses on the interest of chromones for the development of future treatments against leishmaniasis. In addition to plant-based chromone derivatives, structure-activity relationship studies that aim to identify the optimal structural features of the chromones' antileishmanial activity are also described and discussed.

EXPERT OPINION

The numerous examples of chromones depicted in this paper, allied with the SAR studies presented herein, suggest that the chromone scaffold is a privileged core for the design and development of novel antileishmanial agents. However, some concerns have been raised concerning the considerable variability observed in the results throughout the scientific bibliography. These inconsistencies may explain the absence of pharmacodynamic and pharmacokinetic studies as well as clinical trials.

Natural chromones as potential anti-inflammatory agents: Pharmacological properties and related mechanisms

Chromones are a group of natural substances with a diversity of biological activities. Herein we assessed the pharmacological potential of three chromones (1, 2 and 3) isolated from Dictyoloma vandellianum as anti-inflammatory agents using in vitro and in vivo approaches. During in vitro screening, the production of NO and cytokines by macrophages stimulated with LPS and IFN-γ was inhibited by all chromones at concentrations (5-20 μM) that did not induce cytotoxicity. Analysis of pharmacokinetic parameters (in vitro half-life and intrinsic clearance) using human liver microsomes revealed that 3 has a superior pharmacokinetic profile, compared to 1 and 2. Treatment with 3 (100 mg/kg, ip) did not affect the mice motor performance, while 1 and 2 induced motor deficit. Taking into account the pharmacokinetic profile and absence of motor impairment, 3 was selected for further pharmacological characterization. Corroborating the data from in vitro screening, treatment of cell cultures with 3 (5-20 μM) reduced TNF-α, IL-6 and IL-1β production by stimulated macrophages. In the complete Freund's adjuvant-induced paw inflammation model in mice, 3 (25 and 50 mg/kg, ip) inhibited mechanical hyperalgesia, edema and cytokine production/release (IL-1β, IL-6 and TNF-α). 3 (5-20 μM) also reduced the transcriptional activity of NF-κB in stimulated macrophages. Furthermore, treatment with RU486, a glucocorticoid receptor (GR) antagonist, partially prevented the inhibitory effect of 3 on macrophages, indicating that this chromone exerts its anti-inflammatory effects in part through the activation of GR. The results presented herein demonstrate the pharmacological potential of natural chromones, highlighting 3 as a possible candidate for the drug discovery process targeting new anti-inflammatory drugs.

Therapeutic potency of substituted chromones as Alzheimer's drug: Elucidation of acetylcholinesterase inhibitory activity through spectroscopic and molecular modelling investigation

Introduction: Documentation on the potency of chromones as acetylcholinesterase (AChE) antagonists has paved the way for the design and usage of new chromone analogues as inhibitors of AChE modelled on the hypothesis based on cholinergic pathway of Alzheimer's disease (AD). Here, 2 minimally substituted chromones, namely 3-cyanochromone (CyC) and 7-amino-3- methylchromone (AMC), were checked for their AChE inhibition efficacies and plasma protein modulation. Methods: Colorimetric enzymatic assay as well as fluorescence measurements were performed for obtaining the experimental results, which were further corroborated by molecular docking and simulation studies. Results: The investigated systems exhibited strong inhibition activities against AChE, with CyC (IC50= 85.12 ± 6.70 nM) acting as better inhibitor than AMC (IC50 = 103.09 ± 11.90 nM) and both having IC50 values in the range of FDA approved cholinergic drug Donepezil (IC50 = 74.13 ± 8.30 nM). Non-competitive inhibition was observed in both the cases with the inhibitors binding near the peripheral anionic site (PAS) of the enzyme. Having one planar nitrile group in CyC as compared to sp3 hybridised substituents in AMC facilitated stacking interactions in the former, accounting for its higher inhibitory efficacy. A significant decrease in the inhibition potency of CyC (~32%) was noted in comparison with AMC (~5%) when the experiments were performed in presence of human serum albumin (HSA) instead of pure aqueous buffer. Conclusion: This comparative study affirms the importance of meticulous substitution in the chromone scaffold to promote maximum inhibition potency, while considering their usage as AD drugs.

Searching for new cytotoxic agents based on chromen-4-one and chromane-2,4-dione scaffolds

Cancer is a major cause of death worldwide and novel anticancer agents for its better management are much needed. Benzopyrone-based compounds, such as chromones, possess several distinctive chemical and biological properties, of which the cytotoxicity against cancer cells seems to be prominent. In this study, two series of compounds based on chromen-4-one (3-10) and chromane-2,4-dione (11-18) scaffolds were synthesized in moderate/high yields and evaluated for cytotoxicity against HL-60, MOLT-4, and MCF-7 cancer cells using MTT assay. In general, the compounds exhibited moderate cytotoxic effects against the cancer cell lines, among which, a superior potency could be observed against MOLT-4 cells. Chroman-2,4-dione (11-18) derivatives had overall higher potencies compared to their chromen-4-one (3-10) counterparts. Compound 13 displayed the lowest IC₅₀ values against HL-60 (IC₅₀, 42.0 ± 2.7 μM) and MOLT-4 cell lines (IC₅₀, 24.4 ± 2.6 μM), while derivative 11 showed the highest activity against MCF-7 cells (IC₅₀, 68.4 ± 3.9 μM). In conclusion, this study provides important information on the cytotoxic effects of chromone derivatives. Benzochroman-2,4-dione has been identified as a promising scaffold, which its potency can be modulated by tailored synthesis with the aim of finding novel and dissimilar anticancer compounds.

Extracellular chromone derivatives in cell cultures of Pimpinella anisum. Influence of elicitation with methyl jasmonate and 2β-methyl cyclodextrins

OBJECTIVES

To explore the potentiality of undifferentiated Pimpinella anisum L. cell cultures for the production of secondary metabolites by means of elicitation.

RESULTS

Two chromone compounds were secreted to the medium of undifferentiated cultures of P. anisum: 4-methoxyfuro[3,2-g]chromen-7-one, known as bergapten, which is constitutive to anise, and 5-hydroxy-7-methoxy-2-methylchromen-4-one, the rare chromone eugenin, not yet described in P. anisum. Caffeoyl quinic acid species were also identified in the biomass. Elicitation with methyl jasmonate enhanced chromone accumulation in the medium and stimulated phenolic acid metabolism in the biomass (11 mg caffeoyl quinic acids g^-1 DW cells). The application of 2,6-dimethyl-β-cyclodextrins to cultures led to an intense accumulation of chromones, with nearly 10 mg l^-1 bergapten and 150 mg l^-1 eugenin being accumulated extracellularly after optimal elicitation conditions.

CONCLUSIONS

The significant amounts of eugenin obtained in the anise cultures and the stability of production over long periods of time can be of interest for its biotechnological production and for future studies on biosynthesis regulation.

Pyranochromones from Dictyoloma vandellianum A. Juss and Their Cytotoxic Evaluation

One new chromone 3,3-dimethylallylspatheliachromene methyl ether (1), as well as five known chromones, 6-(3-methylbut-2-enyl) allopteroxylin methyl ether (2), 6-(3-methylbut-2-enyl) allopteroxylin (3), 3,3-dimethylallylspatheliachromene (4), 5-O-methylcneorumchromone K (5) and spatheliabischromene (6), two alkaloids, 8-methoxy-N-methylflindersine (7) and 8-methoxyflindersine (8), and two limonoids, limonin diosphenol (9) and rutaevin (10), were isolated from Dictyoloma vandellianum A. Juss (Rutaceae). Cytotoxic activities towards tumor cell lines B16-F10, HepG2, K562 and HL60 and non-tumor cells PBMC were evaluated for compounds 1 - 6. Compound 1 was the most active showing IC₅₀ values ranging from 6.26 to 14.82 μg/ml in B16-F10 and K562 cell lines, respectively, and presented IC₅₀ value of 11.65 μg/ml in PBMC cell line.

Phytochemical constituents and in vitro radical scavenging activity of different Aloe species

The phytochemical profile of Aloe barbadensis Mill. and Aloe arborescens Mill. was investigated using colorimetric assays, triple quadrupole and time-of-flight mass spectrometry, focusing on phenolic secondary metabolites in the different leaf portions. Hydroxycinnamic acids, several characteristic anthrones and chromones, the phenolic dimer feralolide and flavonoids such as flavones and isoflavones were identified. The stable radical DPPH test and the ORAC assay were then used to determine the in vitro radical scavenging. The outer green rind was the most active, while the inner parenchyma was much less effective. The 5-methylchromones aloesin, aloeresin A and aloesone were the most active among the pure secondary metabolites tested. The results suggest that several compounds are likely to contribute to the overall radical scavenging activity, and indicate that leaf portion must be taken into account when the plant is used for its antioxidant properties.

Towards the development of chromone-based MEK1/2 modulators

Inhibition or allosteric modulation of mitogen-activated protein kinase kinases MEK1 and MEK2 (MEK1/2) represent a promising strategy for the discovery of new specific anticancer agents. In this paper, structure-based design, beginning from the lead compound PD98059, was used to study potential structural modifications on the chromone structure in order to obtain highly potent derivatives that target the allosteric pocket in MEK1. Subsequently, a small series of PD98059 analogs were synthesized to provide a first generation of chromone-based derivatives that inhibit the activation of MEK1 with IC50 values as low as 30 nM in vitro. Complementary cellular studies also showed that two of the compounds in the series inhibit the activity of MEK1/2 with IC50 values in the nanomolar range (73-97 nM). In addition, compounds in this series were found to inhibit the proliferation of a small panel of human cancer cell lines.

Blood glucose lowering activity of aloe based composition, UP780, in alloxan induced insulin dependent mouse diabetes model

BACKGROUND

There are a few nutritional approaches to address the increased needs of managing diabetic conditions. Previously it has been reported that UP780, a standardized composition of aloe chromone formulated with an aloe polysaccharide, has a significant impact in reducing HbA1C, fasting blood glucose, fructosamine and plasma insulin level in humans and improved impaired glucose and insulin resistance in high-fat diet-induced and db/db non-insulin dependent diabetic mouse models. Here we describe activity of UP780 and its constituents to improve insulin sensitivity in alloxan induced insulin dependent diabetic mouse model.

MATERIALS AND METHOD

Insulin dependent diabetes was induced by administering a single intraperitoneal injection of alloxan monohydrate at a dose of 150 mg/kg to CD-1 mice. Aloesin (UP394) was formulated with an Aloe vera inner leaf gel powder polysaccharide (Qmatrix) to yield a composition designated UP780. Efficacy of oral administration of UP780 at 2000 mg/kg and its constituents (aloesin at 80 mg/kg and Qmatrix at 1920 mg/kg) were evaluated in this model. Glyburide, a sulfonylurea drug used in the treatment of type 2 diabetes, was used at 5 mg/kg as a positive control. Effect of UP780 on non-diabetic normal mice was also addressed.

RESULTS

Mice administered intraperitoneal alloxan monohydrate developed progressive type-1 diabetes like symptom. After 4 weeks of daily oral administration, reductions of 35.9%, 17.2% and 11.6% in fasting blood glucose levels were observed for UP780, the UP780 Aloe vera inner leaf gel polysaccharide preparation without chromone (Qmatrix), and Aloesin (UP394), treated animals respectively, compared to vehicle treated animals. UP780 has no impact on blood glucose level of non-diabetic healthy mice. UP780 showed statistically significant improvement for blood glucose clearance in oral glucose tolerance tests. Similarly, enhanced improvement in plasma insulin level and statistically significant reduction in triglyceride level was also observed for animals treated with the composition.

CONCLUSION

These findings suggest that UP780, a chromone standardized Aloe based composition, could possibly be used as a natural supplement alternative to facilitate maintenance of healthy blood glucose levels.

Identification and quantification of 5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones in Chinese eaglewood by HPLC with diode array detection and MS

A sensitive and reliable HPLC coupled with diode array detection and MS method was developed and validated for the first time to simultaneously identify and quantify eight characteristic 5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones (THPECs) in Chinese eaglewood. Chromatographic separation was performed on a Zorbax SB C18 column with a gradient of acetonitrile/0.1% formic acid/water as the mobile phase. The MS fragmentation behavior of THPECs was characterized as the successive neutral loss of two molecules of H2 O ([M+H-18-18](+) ) and then two molecules of CO ([M+H-18-18-28-28](+) ), which could be used to differentiate Chinese eaglewood from counterfeits. Validation of the developed analytical method showed good linearity, satisfactory precision, and good recovery. The established method was successfully applied to the simultaneous determination of eight THPECs in ten batches of Chinese eaglewood, which could be used as a tool for the quality control of Chinese eaglewood.

The suppressive effects of Saposhnikovia divaricata (Fangfeng) chromone extract on rheumatoid arthritis via inhibition of nuclear factor-κB and mitogen activated proteinkinases activation on collagen-induced arthritis model

ETHNOPHARMACOLOGICAL RELEVANCE

Saposhnikovia divaricata (SD), called "Fangfeng" in China, is commonly used in clinical compound prescription for treatment of rheumatoid arthritis (RA), but its actions on RA have not been clarified. The present study aims to determine the anti-inflammatory activity of SD chromone extract (SCE), the major bioactive component of SD, on collagen-induced arthritis (CIA) rats, and elucidate its underlying mechanisms with regards to its molecular basis of action on human fibroblast-like synoviocytes derived from RA patients (HFLS-RA).

MATERIALS AND METHODS

CIA model on rats was constructed by injection of bovine type II collagen. Rats were pre-treated with different dosages of SCE from 3 days before till 35 days after model building. The progression of CIA was evaluated by macroscopic scoring, X-ray observation and hematoxylin and eosin (HE) staining of paws. HFLS-RA were pre-treated with different concentrations of SCE prior to stimulation with 10 ng/ml of tumor necrosis factor (TNF) α. By radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA), levels of interleukin (IL)-1β, IL-6, TNFα and prostaglandin E2 (PGE2) were quantified respectively. Nuclear factor (NF-κB) p65 expression and DNA-binding activity were tested by immunohistochemisty and electrophoretic mobility shift assay (EMSA) respectively. Phosphorylation of extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38 MAPKs were examined by immunohistochemisty staining and western blot analysis.

RESULTS

Histological examination and radiological observation demonstrated that SCE significantly reduced the inflammatory responses in the joints of CIA rats. SCE inhibited the production of TNFα, IL-1β, and IL-6 in the joint tissues and sera. The level of PGE2 in sera was also decreased by SCE. Moreover, SCE treatment in vivo was able to reduce protein level of NF-κB, the transcriptional factor closely related to the inflammatory process, in articular synovium and cartilage of CIA rats. In addition, SCE inhibited p-ERK, p-JNK and p-p38 expression, which were considered to be involved in the phosphorylation of transcription factor NF-κB and the transcription of pro-inflammatory factors. Further, SCE inhibited NF-κB DNA binding activity and attenuated the phosphorylation of ERK, JNK and p38 MAPKs, in a concentration-dependent manner in cultured HFLS-RA.

CONCLUSION

These results highlight the anti-arthritic potential of SCE, and provide further evidence of the involvement of the NF-κB and MARKs inhibition in the effects of SCE.

Synthesis, docking study and relaxant effect of 2-alkyl and 2-naphthylchromones on rat aorta and guinea-pig trachea through phosphodiesterase inhibition

Chromone (4), which form the base structure of various flavonoids isolated as natural products, is capable of relaxing smooth muscle. This is relevant to the treatment of high blood pressure, asthma and chronic obstructive pulmonary disease. The former disorder involves the contraction of vascular smooth muscle (VSM), and the latter two bronchoconstriction of airway smooth muscle (ASM). One of the principal mechanisms by which flavonoids relax muscle tissue is the inhibition of phosphodiesterases (PDEs), present in both VSM and ASM. Therefore, a study was designed to analyze the structure-activity relationship of chromone derivatives in vaso- and bronchorelaxation through the inhibition of PDE. Docking studies showed that these chromones bind at the catalytic site of PDEs. Consequently, we synthesized analogs of chromones substituted at position C-2 with alkyl and naphthyl groups. These compounds were synthesized from 2-hydroxyacetophenone and acyl chlorides in the presence of DBU and pyridine, modifying the methodology reported for the synthesis of 3-acylchromones by changing the reaction temperature from 80 to 30°C and using methylene chloride as solvent, yielding the corresponding phenolic esters 10a-10h. These compounds were cyclized with an equivalent of DBU, pyridine as solvent, and heated at reflux temperature, yielding the chromones 11a-11h. Evaluation of the vasorelaxant effect of 4, 11a-11h on rat aorta demonstrated that potency decreases with branched alkyl groups. Whereas the EC50 of compound 11d (substituted by an n-hexyl group) was 8.64±0.39 μM, that of 11f (substituted by an isobutyl group) was 14.58±0.64 μM. Contrarily, the effectiveness of the compound is directly proportional to the length of the alkyl chain, as evidenced by the increase in maximal effect of compound 11c versus 11d (66% versus 100%) and 11e versus 11f (60% versus 96%). With an aromatic group like naphthyl as the C-2 substituent, the effectiveness was only 43%. All compounds tested on guinea pig trachea showed less than 55% effectiveness. Compounds 4, 11a-11h were evaluated as PDE inhibitors in vitro, with 11d showing the greatest effect (73%), corroborating the importance of a long alkyl chain, which inhibits the decomposition of cGMP. Docking studies showed that the compound 11d was selective for the inhibition of PDE-5.