Antioxidant Activity and α-glucosidase Inhibitory Activity of Sweet Potato(Ipomoea batatas L.)Leaf Extracts from Different Varieties

This study aims to investigate the antioxidant and hypoglycemic potentials of sweet potato(Ipomoea batatas L.)leaves by comparing antioxidant activity and α-glucosidase inhibitory activity of sweet potato leaf extracts from 7 varieties. The content of total polyphenols and flavonoids in sweet potato leaves was measured. The antioxidant activity(DPPH· scavenging ability,ABTS⁺· scavenging ability,·OH scavenging and reducing ability)and α-glucosidase inhibitory activity were evaluated by in vitro experiments. The results showed that there were significant differences in the content of total polyphenols and flavonoids,antioxidant activity and α-glucosidase inhibitory activity among sweet potato leaf extracts from 7 varieties. The content of total polyphenols in sweet potato leaves ranged from 15.02 to 33.33 mg GAE/g DW,and the content of total flavonoids from 1.06 to 3.11 mg RE/g DW. The content of total polyphenols and flavonoids was the highest in sweet potato leaves of Xushu 18,Jishu 18 and Longshu 9,without statistical differences(P>0.05). Free radical scavenging ability(DPPH·,ABTS⁺·,·OH)was the highest in Longshu 9. The reducing ability was the highest in Jishu 18. Shangshu 19 presented the highest α-glucosidase inhibitory activity. The content of total polyphenols and flavonoids showed an extremely positive correlation with antioxidant activity(P<0.01),but no obvious correlation with α-glucosidase inhibitory activity(P>0.05). This study demonstrates that sweet potato leaves are a good source of potential antioxidants and α-glucosidasee inhibitors,providing a theoretical basis for sweet potato cultivation and the selection of sweet potato varieties.