Determination of total antioxidant capacity of green teas by the ferric reducing/antioxidant power assay
The tea plant (Camellia sinesis L.) is grown in about 30 countries worldwide (Graham, 1992). It grows best in tropical and subtropical areas with adequate rainfall, good drainage, and slightly acidic soil (Graham, 1999). Tea (Camellia sinesis) is also the most widely consumed beverage worldwide for its desirable aroma, taste and putative positive physiological functions (Zhu et al., 2002; Balentine, 1992). The type and quantity of tea taken varies in different countries and races (Weisburger, 1996; Kohlmeier, 1997). Tea contains large amounts of polyphenolic compounds with antioxidant properties, and these may prevent oxidative damage of DNA (Wiseman et al., 1997; Zhang and Shen, 1997). Tea is also rich in flavonoids and other polyphenols that have been shown to possess a wide range of biological and pharmaceutical benefits, including anticarcinogenic, antioxidative, and hypolipidemic activities (Buschman, 1998; Yang, 1999). These beneficial effects are may be attributed to tea’s antioxidant activity, e.g., free radical scavenging and metal chelating abilities. Studies have shown green tea has anti-inflammatory (Tipoe et al., 2007), cholesterol lowering (Koo and Noh, 2007), antiviral and antibacterial properties (Weber et al., 2003; Friedman et al., 2006). Based on results mainly from animal studies, many companies are supplementing their skin care products with green tea extracts (Katiyar and Elmets, 2001). However few studies have been conducted to investigate the antioxidant activity of Iranian consumed green tea samples.