This study considers a laboratory examination of the antioxidant performance of methanolic extracts from the leaves and stems of 3 common wild grapes (Vitis thunbergii,V. flexuosa, andV. kelungeusis) by variousin vitromethods. It also seeks to identify the specific antioxidant constituent. Results revealed that, of these specimens, stem extracts ofV. thunbergiiexhibited good 1,1-diphenyl-2-picrylhydrazyl radical-scavenging and superoxide radical-scavenging performance and ferrous ion-chelating ability, as well as the highest total phenolic content (179.5 mg of GAE/g). The principal antioxidant, (+)-lyoniresinol-2a-O-β-d-glucopyranoside, was isolated from the stem extracts ofV. thunbergiiand identified. Removal of this compound from the extracts caused an approximate 2- to 5-fold decrease in antioxidant performance. This showed that (+)-lyoniresinol-2a-O-β-d-glucopyranoside is the primary antioxidant in wild grapes. Results also indicated that the antioxidant performance of (+)-lyoniresinol-2a-O-β-d-glucopyranoside was stronger than its lignan aglycone, (+)-lyoniresinol.
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