Raju Gautam

Recent developments in anti-inflammatory natural products

Many of the inflammatory diseases are becoming common in aging society throughout the world. The clinically used anti‐inflammatory drugs suffer from the disadvantage of side effects and high cost of treatment (in case of biologics). Alternative to these drugs are traditional medicines and natural products, which offer a great hope in the identification of bioactive lead compounds and their development into drugs for treating inflammatory diseases. Since ancient times traditional medicines and phytopharmaceuticals are being used for the treatment of inflammatory and other disorders. The present review article describes anti‐inflammatory natural products derived from plants and marine sources reported during last decade. The compounds described belong to different chemical classes such as alkaloids, steroids, terpenoids, polyphenolics, phenylpropanoids, fatty acids and lipids, and various miscellaneous compounds. The attempt is also being made to enumerate the possible leads, e.g. curcumin, resveratrol, baicalein, boswellic acid, betulinic acid, ursolic acid, and oleanolic acid, for further development with the help of structure–activity relationship (SAR) studies and their current status. In addition SAR studies carried out on the anti‐inflammatory activity of flavonoid compounds and clinical studies performed on anti‐inflammatory natural products are also discussed.

Anti-inflammatory effect of Ajuga bracteosa Wall Ex Benth. mediated through cyclooxygenase (COX) inhibition.

ETHNOPHARMACOLOGICAL RELEVANCE Ajuga bracteosa Wall Ex Benth. (Labiateae) is described in Ayurveda for the treatment of rheumatism, gout, palsy and amenorrhea. AIM OF THE STUDY The aim of present investigation is to study anti-inflammatory activity of Ajuga bracteosa, to understand possible mechanism of action and to identify the constituents responsible for its activity. MATERIALS AND METHODS The anti-inflammatory activity of 70% ethanolic extract was evaluated in TPA-induced mouse ear edema assay and in vitro cyclooxygenase (COX)-1 and COX-2 inhibitory activity was determined using EIA kits employing appropriate reference standards. Aajugarin I, lupulin A, withaferin A, reptoside and 6-deoxyharpagide were isolated from the 70% ethanolic extract by silica gel column chromatography. RESULTS The 70% ethanol extract of whole plants of Ajuga bracteosa showed a significant (p<0.05) and dose-dependent anti-inflammatory activity in an acute inflammation model at the dose of 0.5 and 1.0 mg/ear. The extract also exhibited a strong in vitro COX-1 and COX-2 inhibitory activity at 25 and 50 μg/mL concentration. Among the isolated compounds 6-deoxyharpagide exhibited highest COX-2 inhibition while rest of the compounds exhibited weak to moderate COX-1 and COX-2 inhibition at 30 μM concentration. CONCLUSIONS The results suggest that the 70% ethanol extract of Ajuga bracteosa possesses promising anti-inflammatory activity, which is possibly mediated through inhibition of COX-1 and COX-2 enzymes. The isolated constituents could be responsible in part for its anti-inflammatory and COX inhibitory activity. The study supports traditional use of Ajuga bracteosa for inflammatory diseases.

Synthesis, biological evaluation and molecular docking studies of stellatin derivatives as cyclooxygenase (COX-1, COX-2) inhibitors and anti-inflammatory agents

Stellatin (4), isolated from Dysophylla stellata is a cyclooxygenase (COX) inhibitor. The present study reports the synthesis and biological evaluation of new stellatin derivatives for COX-1, COX-2 inhibitory and anti-inflammatory activities. Eight derivatives showed more pronounced COX-2 inhibition than stellatin and, 17 and 21 exhibited the highest COX-2 inhibition. They also exhibited the significant anti-inflammatory activity in TPA-induced mouse ear edema assay and their anti-inflammatory effects were more than that of stellatin and indomethacin at 0.5mg/ear. The derivatives were further evaluated for antioxidant activity wherein 16 and 17 showed potent free radical scavenging activity against DPPH and ABTS radicals. Molecular docking study revealed the binding orientations of stellatin and its derivatives into the active sites of COX-1 and COX-2 and thereby helps to design the potent inhibitors.

Anti-inflammatory, cyclooxygenase inhibitory and antioxidant activities of standardized extracts of Tridax procumbens L.

The standardized EtOAc, MeOH and 70% EtOH extracts of Tridax procumbens aerial parts showed significant inhibition of rat paw edema at a medium dose of 200mg/kg and the EtOAC extract was the most active. These extracts were standardized by HPLC with the help of chemical markers. Further, the extracts were evaluated for COX-1 and COX-2 inhibitory activity and EtOAc extract exhibited the highest inhibition of COX-1 and COX-2 at 50 μg/mL. Cent aurein, centaureidin and bergenin were isolated as COX-1 and COX-2 inhibitory principles from the EtOAc extract. The extracts also exhibited antioxidant activity against DPPH and ABTS free radicals. The anti-inflammatory activity of T. procumbens aerial parts could be at least in part due to COX-1, COX-2 enzyme inhibition and free radical-scavenging activities which may be attributed to the presence of flavonoids and other polyphenols in the extracts.

Anti-inflammatory, cyclooxygenase (COX)-2, COX-1 inhibitory, and free radical scavenging effects of Rumex nepalensis.

Evaluation of the topical anti-inflammatory activity of chloroform and ethyl acetate extracts of RUMEX NEPALENSIS roots in a TPA-induced acute inflammation mouse model demonstrated a significant reduction in ear edema. The extracts were further tested on purified enzymes for COX-1 and COX-2 inhibition to elucidate their mechanism of action, and a strong inhibition was observed. Six anthraquinones and two naphthalene derivatives were isolated from the ethyl acetate extract. Among the isolated compounds, emodin was found to be a potent inhibitor with slight selectivity towards COX-2, and nepodin exhibited selectivity towards COX-1. Emodin, endocrocin, and nepodin also exhibited significant topical anti-inflammatory activity in mice. Interestingly, nepodin showed better radical scavenging activity than trolox and ascorbic acid against DPPH and ABTS radicals. The strong radical scavenging activity of chloroform and ethyl acetate extracts could be explained by the presence of nepodin as well as by the high phenolic content of the ethyl acetate extract. Thus, the anti-inflammatory effect of R. NEPALENSIS roots was assumed to be mediated through COX inhibition by anthraquinones and naphthalene derivatives and through the radical scavenging activities of naphthalene derivatives.

Anti-inflammatory, cyclooxygenase (COX)-2, COX-1 inhibitory and antioxidant effects of Dysophylla stellata Benth.

The n-hexane and ethyl acetate extracts of whole plants of Dysophylla stellata significantly inhibited edema when applied topically at doses of 0.5 and 1mg/ear in TPA-induced ear edema assay in mice. Further, both the extracts were evaluated for COX-1 and COX-2 inhibitory activities and showed 85.42 and 57.38%; and 71.79 and 89.27% inhibition at 50 microg/ml, respectively. Chromones (1 and 2) present in these extracts could be responsible for their COX-1 and COX-2 inhibitory and anti-inflammatory activities. The ethyl acetate extract showed antioxidant activity in DPPH and ABTS radical scavenging assay where as n-hexane extract found to be inactive.

Simultaneous determination of naphthalene and anthraquinone derivatives in Rumex nepalensis Spreng. Roots by HPLC: comparison of different extraction methods and validation

INTRODUCTION Rumex nepalensis contains mainly anthraquinone and naphthalene derivatives. Although HPLC methods have been reported for the analysis of anthraquinones, neither a phytochemical analysis of Rumex species nor the simultaneous determination of anthraquinone and naphthalene derivatives in other samples has been reported so far. OBJECTIVE To develop and validate a HPLC method for the simultaneous determination of anthraquinone and naphthalene derivatives in R. nepalensis roots. METHODOLOGY Anthraquinones and naphthalenes were extracted from R. nepalensis roots by three methods (reflux, ultrasonication and pressurized liquid extraction) using methanol. Separation was achieved on an RP C₁₈ column with a gradient mobile phase consisting of 0.05% orthophosphoric acid in water (solvent A) and methanol (solvent B) using a UV detector (254 nm). RESULTS Small differences were observed in the contents of anthraquinone and naphthalene derivatives extracted by the three methods. Chrysophanol-8-O-β-D-glucopyranoside and nepodin were detected as major constituents. The method showed a good linearity (r² > 0.9992), high precision (RSD < 5%) and a good recovery (97-105%) of the compounds. The lowest detection limit was found to be 0.97 ng and the method was found to be robust. CONCLUSION Reflux and ultrasonication were found to be the best suited methods for the extraction of glycosides and aglycones, respectively. The developed and validated HPLC method is simple, precise and accurate; and can hence be recommended as the method of choice for the analysis of anthraquinones and naphthalenes in R. nepalensis and other Rumex species for both quality control as well as routine analytical purposes.

Synthesis and biological evaluation of arylidene analogues of Meldrum’s acid as a new class of antimalarial and antioxidant agents

A series of arylidene analogues of Meldrums acid were synthesized and evaluated for in vitro antimalarial and antioxidant activities for the first time. The influence of various physico-chemical parameters such as dielectric constant (epsilon), donor number (DN), acceptor number (AN), hydrogen bond donor (HBD), hydrogen bond acceptor (HBA), and solubilizing power of the solvents on Meldrums acid anion generation and thus on promoting the Knoevenagel condensation of Meldrums acid with aryl aldehydes has been discussed. Five compounds 9l, 9m, 9n, 9r, and 9s were found to be most active against Plasmodiumfalciparum with IC(50) values in the range of 9.68-16.11 microM. Compound 9l exhibited the most potent antimalarial activity (IC(50) 9.68 microM). The compounds were also found to possess antioxidant activity when tested against DPPH and ABTS free radicals.