Effects of yam tuber protein, dioscorin, on attenuating oxidative status and learning dysfunction in d-galactose-induced BALB/c mice.

The yam tuber is a traditional Chinese medicine used in long-term treatment as a juvenescent substance. The purified yam tuber's major water-soluble protein, dioscorin, and its protease hydrolysates have been reported to have several biological activities. In this study, d-galactose (Gal) was subcutaneously injected into the dorsal necks of BALB/c mice daily for 10weeks (Gal group) to induce oxidative stress. By the fifth week, 20 or 80mg dioscorin/kg was orally administered daily combined with a daily Gal injection until the end of the study. The plasma malondialdehyde (MDA) level and advanced glycation end-products obtained after dioscorin oral administrations were lower compared to the Gal group. In addition, the latency and swimming distance in the mice that received dioscorin administration were significantly improved compared to the Gal group in the Morris water maze. Dioscorin administration resulted in higher GSH levels and oxygen radical antioxidant capacity (ORAC) activity and lower MDA and inducible nitric oxide synthase (iNOS) levels in the brain compared to mice in the Gal group. These elevated antioxidant activities following oral administration of yam dioscorin in vivo may reflect traditional juvenescent uses with the potential for anti-aging treatments.