Tetrahydroamentoflavone (THA) from Semecarpus anacardium as a potent inhibitor of xanthine oxidase

Ethnopharmacological relevance: Seed of Semecarpus anacardium L is widely used in Indian traditional medicine; Ayurveda and Sidha, for treatment of inflammatory disorders and gout. Aim of the study: The present study was aimed at isolation of a compound for its potential to inhibit xanthine oxidase (XO), over expression of which lead to inflammation and gout. Materials and methods: Activity guided fractionation of S. anacardium seed was conducted using liquid-liquid partition and preparative HPLC. The fractions were evaluated for their XO inhibition and antioxidant activity. The ethyl acetate fraction with the highest XO activity yielded a biflavonoid compound tetrahydroamentoflavone (THA). Lineweaver-Burk (LB) plot for the XO inhibition of THA and allopurinol was constructed from the kinetic data. Results: IC50 values of THA and allopurinol for XO inhibition were 92 and 100 nM respectively and their corresponding values for K-i were 0.982 and 0.612 mu M respectively. Conclusion: THA was a potent XO inhibitor which could be considered as a drug candidate or chemopreventive agent, after establishing its pharmacological and clinical evaluation. The study results appear to support the claim of the traditional medicine with respect to the efficacy of S. anacardium seed against inflammation and gout. (C) 2010 Published by Elsevier Ireland Ltd.