DETERMINATION OF TOTAL ANTIOXIDANT CAPACITY OF GREEN TEAS BY THE FERRIC REDUCING/ANTIOXIDANT POWER ASSAY

Green tea is one of the important sources of bioactive compounds which have been used in folk medicine for many centuries. This study aimed to compare in vitro antioxidant power of different types of green tea (Camellia sinensis). Antioxidant activity of methanolic (50%) extracts of five green tea samples was investigated according to Ferric reducing ability power method. Total phenolic contents were analyzed using a spectrophotometric technique, based on the Folin-ciocalteau reagent, and calculated as gallic acid equivalents per gram dry weight. Total flavonoid and antocyanidin were also investigated according to aluminum chloride and vanillin colorimetric assay respectively. Total antioxidant activity varied from 0.554±0.042 in Avicen green tea sample to 3.082±0.150 mmoL FeII/g in Chinas green tea and total phenolic content ranged from the 0.030±0.001 in Avicen green tea sample to 0.196±0.012 g gallic acid per gram dry weight in Ahmad green tea. A linear positive relationship existed between the antioxidant activity, total phenolic, flavonoid and antocyanidin content of the tested green tea samples. Green tea samples possess relatively high antioxidant activity due to contribution of phenolic compounds. The present study showed that green tea samples which are more frequently consumed in Iran are strong radical scavengers and can be considered as good sources of natural antioxidants for medicinal and commercial uses.