Natural antioxidant potential of selected underutilized wild yams (Dioscorea spp.) for health benefit

Modern research is directed towards finding naturally-occurring antioxidants of plant origin for improving nutrition and health benefit. Wild yam species are used as indigenous food and medicine by various tribal groups of Koraput, India. However, detailed analysis of health promoting bioactive compounds and antioxidant properties are lacking. The present study aims to evaluate the flavonoid, total antioxidant capacity and in vitro antioxidant activity of different wild and cultivated Dioscorea species of Koraput. The extract of these tuber was screened for its potential antioxidant activities by various tests, such as DPPH, nitric oxide, superoxide and ABTS radical cation assay. The phenol, flavonoid and total antioxidant capacity of the samples were ranged from 2.19 to 9.62 mg g^-1 dry weight, 0.62-0.85 mg g^-1 dry weight and 1.63-5.59%, respectively. The IC₅₀ values were 77.9-1164, 101.2-1031.6, 27.0-1022.6 and 47.1-690 µg ml^-1 for DPPH, ABTS, superoxide and nitric oxide scavenging activity, respectively. Taken together, some wild yam species such as D. bulbifera, D. pubera and D. pentaphylla had significantly higher flavonoids content and antioxidant capacity along with the lower IC₅₀ values than the standards in compared to the other species. The present studies confirmed that some wild yam tubers have superior potential for scavenging deleterious free radicals effectively. Results indicated that these wild yam species should be promoted as natural source of antioxidants.