Tannin fraction from Ampelopsis grossedentata leaves tea (Tengcha) as an antioxidant and α-glucosidase inhibitory nutraceutical

Leaf of Ampelopsis grossedentata is a new resource of functional foods with healthful properties. Antioxidant and -glucosidase inhibitory activities of water extract (made in the style of drinking), tannin fraction (TF) and dihydromyricetin (DMY) from A.grossedentata leaves were evaluated. The main component of TF was identified as gallotannins. DPPH and ABTS radical scavenging activities and reducing power of TF were superior to those of water extract, however, inferior to those of DMY. In no PBS wash protocol of cellular antioxidant activity assay, DMY and TF exhibited similarly, while in PBS wash protocol, the value of TF was higher than that of DMY. In addition, TF possessed the highest -glucosidase inhibitory activities (IC50=1.94gmL(-1)), followed by water extract (IC50=23.10gmL(-1)) and DMY (IC50=72.21gmL(-1)). The strong -glucosidase inhibitory activity of TF may attribute to the binding capacity to enzymes, as confirmed by fluorescence analysis.