Antioxidative activity of water extract of sweet potato leaves in Taiwan

This study reports the preparation of four varieties of water extract from sweet potato leaves from Taiwan, including TNG10, TNG57, TNG66 and YSP, and evaluates their antioxidative activity. The EC50 values (scavenging DPPH radicals) of TNG10, TNG57, TNG66 and YSP were 0.27 ± 0.01, 0.19 ± 0.01, 0.41 ± 0.02, and 0.31 ± 0.02 mg/ml, respectively, on a freeze-dry weight basis. The total phenolic contents of these water extracts were in the order: TNG57 > TNG10 > TNG66 > YSP. The TNG10 and TNG57 extracts exhibited better reducing power and scavenging effects of superoxide radicals than did TNG66 and YSP. At a concentration of 1 mg/ml, TNG10 and TNG57 significantly protected HaCaT cells from H2O2-induced cytotoxicity. The water extracts of YSP had more flavonoids than had those of TNG66 which may have contributed to their higher activity in many antioxidative assays. These results suggest that the water extracts of all four varieties of sweet potato leaves, and especially TNG10 and TNG57, display potent antioxidative effects.