ANTIOXIDANT PROPERTIES OF WATER EXTRACTS FROM PARCHING GREEN TEA

Cold and hot water extracts (2, 6 and 10%) were prepared from parching green tea and its antioxidant properties studied and potential antioxidant components determined. Yields of hot water extracts (17.53-28.63%) were significantly higher than those of cold water extracts (13.34-16.14%). The half maximal effective concentration (EC50) values in antioxidant activity and reducing power were 2.17-2.75 and 0.22-0.30 mg/mL, respectively. Scavenging abilities on 1,1-diphenyl-2-picrylhydrazyl radicals were comparable. EC50 values in scavenging ability on hydroxyl radicals and chelating ability on ferrous ions were 3.31-4.54 and 1.63-3.09 mg/mL, respectively. Contents of total phenols were 220.52-339.83 mg/g whereas those of total catechins in cold and hot water extracts were 130.22-146.28 mg/g and 136.40-191.33 mg/g, respectively. Based on the results obtained, hot water extracts were more effective in antioxidant activity, reducing power and scavenging ability on hydroxyl radicals but less effective in chelating ability on ferrous ions. PRACTICAL APPLICATIONS Tea is one of popular drinks in the world. The consumption of green tea is especially popular in Asia, mainly for its health benefits. Parched tea is a Chinese style green tea, which is different from the Japanese style steamed tea. Recently, the tea prepared by brewing tea leaves in cold water has become a new choice in Taiwan in addition to traditionally hot water-brewed tea. Results from this research, the cold and hot water extracts of green tea are good antioxidant. Besides, green tea is also reported to reduce serum cholesterol levels and inhibit hypertension, mutagenesis, and tumourigenesis in several experiments in vitro and in vivo. Therefore, the extract of green tea has the potential to be developed into new health foods, and the cold brewing would be a new alternative way to make a tea.