Xanthine oxidase inhibitory activity of the methanolic extracts of selected Jordanian medicinal plants

Background: The search for novel xanthine oxidase (XO) inhibitors with a higher therapeutic activity and fewer side effects are desired not only to treat gout but also to combat various other diseases associated with the XO activity. At present, the potential of developing successful natural products for the management of XO-related diseases is still largely unexplored. In the present study, we have screened the methanolic extracts of various Jordanian medicinal plants for their XO inhibitory activities using an optimized protocol. Materials and Methods: The methanolic extracts of 23 medicinal plants, belonging to 12 families, were tested in vitro, at 200 µg/ml concentrations, for their XO inhibitory potential. The dose-dependent inhibition profiles of the most active plants were further evaluated by estimating the IC50 values of their corresponding extracts. Results: Six plants were found most active (% inhibition more than 39%). These plants are Salvia spinosa L. (IC50 = 53.7 µg/ml), Anthemis palestina Boiss. (168.0 µg/ml), Chrysanthemum coronarium L. (199.5 µg/ml), Achillea biebersteinii Afansiev (360.0 µg/ml), Rosmarinus officinalis L. (650.0 µg/ml), and Ginkgo biloba L. (595.8 µg/ml). Moreover, four more plants, namely Lavandula angustifolia Mill. (28.7% inhibition), Helianthemum ledifolium (L.) Mill. (28.4%), Majorana syriaca (L.) Kostel. (25.1%), and Mentha spicata L. (22.5%) showed a XO inhibitory activity in the range of 22–30%. Conclusion: The study showed that many of the tested plant species are potential sources of natural XO inhibitors that can be developed, upon further investigation, into successful herbal drugs for treatment of gout and other XO-related disorders.