The polyphenolic composition and radical scavenging properties of Kenyan tea cultivars
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Interest in medicinal and health enhancing properties of functional components in foods continues to arouse a lot of interest. Polyphenolic fractions in tea are potent bioactive molecules. In this study, the polyphenolic composition of 25 different types of Kenyan tea cultivars was determined using the HPLC and the Folins Ciocalteus spectrophotometric methods. Total polyphenols, total catechins, individual catechins and antioxidant activity were significantly (P < 0.05) different among tea varieties, with green tea having the highest levels of total polyphenols ranging from 19.70% to 26.12%, TC (8.51% to 17.60%), individual catechins, and AA (86.65% to 94.50%). In vitro bioassay carried out using 2, 2'-diphenyl picryl hydrazyl radical showed epigallocatechin gallate was the most potent catechin and the most potent in antioxidant activity (r = 0.968***). Epigallocatechin (r = 0.659***, P < 0.001), epicatechigallate (r = 0.454*, P < 0.001), and epicatechin (EC) (r = 0.780***, P < 0.001), showed significant (P < 0.05) antioxidant activity. Black tea contained high levels of theaflavins and thearubigins (2.072% to 17.12%), respectively which accounted for its antioxidant activity (r = 0.803*** and r = 0.859***, respectively). Gallic acid also showed significant (r = 0.530*) contribution to the antioxidant activity in black tea. Data obtained from this study reveals that different Kenyan tea cultivars have different polyphenolic composition which imparts on their unique biochemical qualities. Cultivar type is therefore a critical factor in determining the antioxidant potency of tea product and that black tea processed from suitable cultivars could be potent in antioxidant activity when compared to green tea. Green and white tea products are rich in catechins, black tea products are rich in TFs and TRs while purple tea is rich in anthocyanins.