Total Polyphenol Content and Antioxidative Activity of Wild Grape (Vitis coignetiae) Extracts Depending on Ethanol Concentrations

As an oriental medicinal plant, wild grape (WG, Vitis coignetiae) has been known to contain abundant nutrients compared to grape (Vitis vinifera L.) and as a source of stilbenes, a kind of polyphenol. This study was performed to investigate the antioxidative activity of WG extracts by measuring electron donating ability (EDA), nitrite scavenging ability (NSA), super oxide dismutase (SOD)-like activity and total polyphenol content (TPC). The extracts were obtained using microwave-assisted extraction (microwave power: 90 W, extraction time: 5 min, extractant: water, 50 and 100% ethanol). EDAs, SOD-like activities and TPCs were the highest at 50% ethanol extracts while conversely lowest at 100% ethanol extracts. EDAs of 50% and 100% ethanol extracts at 1.6 g/dL concentration, 97.70±0.55 and 98.05±0.36%, were higher than those of 0.1 and 1% L-ascorbic acids, 101.44±0.98% and 99.43±0.78%, respectively. At the concentration of 1.6 g/dL, 50% ethanol extract showed lower NSA (pH 1.2) than water extract unlike EDA, TPC and SOD-like activity. Regarding TPCs of WG extracts, the activities were the highest at 50% ethanol extracts (1.6 g/dL: 38.76±0.23 mM gallic acid equiv.) followed by water and 100% ethanol extracts. The results suggest the usefulness of developing functional foods using antioxidative active compounds of WG with high polyphenol contents.