In Vitro Xanthine Oxidase Inhibition by Selected Jordanian Medicinal Plants

In the present study, 18 Jordanian medicinal plants were evaluated for their Xanthine Oxidase (XO) inhibitory potential. Their aqueous extracts, prepared from used parts, were tested in vitro, at 200 µg/mL concentration, for their inhibition potencies expressed as % inhibition of XO activity. Five of the tested plants were found most active (% inhibition more than 35%) and their inhibition profiles (dose-dependent) were further evaluated by estimating the IC50 values of their corresponding extracts. These plants were Hyoscyamus reticulatus L. (IC50 = 12.8 µg/mL), Achillea fragrantissima (Forssk.) Sch. Bip. (197.6 µg/mL), Pimpinella anisum L., (300.4 µg/mL), Origanum syriacum L. (317.0 µg/mL), and Origanum vulgare L. (403.9 µg/mL). Moreover, five more plants showed XO inhibitory activity in the range of 14-30%. Namely: Daphne linearifolia L. (29.5% inhibition), Hibiscus sabdariffa L. (19.4%), Aristolochia maurorum L. (15.6%), Citrullus colocynthis (L.) Schr. (14.4%), and Laurus nobilis L. (13.97%). Considering the results of the present screening study, many of the investigated plant species can be used as potential sources of natural XO inhibitors that can be elaborated as successful herbal remedies for gout, arthritis and other XO-related disorders.