Phytochemical analysis, antioxidant and xanthine oxidase inhibitory activity of Tephrosia purpurea Linn. root extract

An attempt has been made to search for xanthine oxidase (XO) inhibitors from the root extracts of Tephrosia purpurea Linn. which is traditionally used in folk medicine in India. Root extracts were screened for in vitro antioxidant and xanthine oxidase inhibitory activity. Antioxidant activity was measured using ABTS, DPPH, FRAP and ORAC methods. The enzyme inhibitory activity was tested on purified milk xanthine oxidase. The root extracts and phytochemicals, obtained in distilled water, inhibited bovine milk XO in a concentration-dependent manner, with an additional superoxide scavenging capacity, the average antioxidant activity of T. purpurea root extract in the concentration range of 100-200 μg/mL. The reacting system revealed significant antioxidant activity, viz. 42.2 (ABTS), 28.7 (DPPH), 36.5 (FRAP) and 25.6 per cent by ORAC assay. Screening of xanthine oxidase inhibitory activity by extract in terms of kinetic parameters revealed noncompetitive mode of inhibition, where the Km and Vmax values in presence of (25 to 100 μg/mL) T. purpurea root extract is 0.18 μg and 0.040,0.037,0.034 and 0.030 (μg/min) while for control Km and Vmax is 0.21 μg and 0.043 (μg/min), respectively. The phytochemical analysis revealed presence of significant amount of polyphenols and flavonoids (90% and 80%, respectively). These findings suggest that T. purpurea root extract possess prominent medicinal properties and can be exploited as natural drug to treat the diseases associated with free radical formation, oxidative stress and xanthine oxidase activity.