Studies on antioxidant and xanthine oxidase inhibitory activities of Coccinia grandis (L.) Voigt, Datura metel (Linn.) and Tagetes patula (L.) from Rupandehi district of Nepal

In this study, we chose three traditionally used medicinal plants (T. patula, D. metel and C. grandis) to examine their bioactive constituents and xanthine oxidase inhibition potential. Phytochemical screening of studied plant leaf extracts showed these plants as rich resources of secondary metabolites such as alkaloids, flavonoids, phenols, etc. Calculations of TPC and TFC value of plant extracts showed that T. patula content highest value of TPC (630.839±2.633mgGAE/g) and TFC (79.605±1.808mgQE/g) respectively. DPPH and FRAP assay showed D. metel leaf extract as a potent antioxidant among the selected three plant extracts with IC₅₀ values of 0.039 mg/mL and 357.0365±0.682317mm Fe (II)/L respectively. In the antibacterial assay, T. patula leaf only showed the activity of 10mm ZOI value at a concentration of 50 mg/mL as compared to standard drug neomycin against S. aureus while other plant extracts did not show any activity. In the xanthine oxidase inhibition assay, the methanol leaf extract of C. grandis with an IC₅₀ value of 0.491 mg/mL showed the highest xanthine oxidase inhibition activity among selected plants followed by T. patula with an IC₅₀ value of 0.708mg/mL. The results, obtained here provide scientific support for the use of T. patula L. D. metel L. and C. grandis L, Nepal origin in traditional medicine for the treatment of gout. This is the first report on the T. patula leaves extract for xanthine oxidase inhibition activity.