Identification of the anthocyanins from the purple leaf coloured tea cultivar Zijuan (Camellia sinensis var. assamica) and characterization of their antioxidant activities

Zijuan (Camellia sinensis var. assamica) is the most well-known representative of purple leaf coloured anthocyanin-rich tea cultivars in China. Herein, its anthocyanin composition has been investigated for the first time. Eight anthocyanins, pelargonidin-3,5-diglucoside, cyanidin-3-O-galactoside, cyanidin-3-O-glucoside, delphinidin, cyanidin, pelargonidin, peonidin, and malvidin were identified using HPLC and LC-MS and by comparison of their retention times, elution order and MS spectra to authentic standards. Cyanidin-3-O-galactoside was found to be the most abundant. Anthocyanins are generally enriched in tender Zijuan tea leaves, and the green tea processing, especially roasted green tea, can effectively retain the vast majority of the anthocyanins originally present in the fresh leaves compared with those for Oolong tea and black tea. The antioxidant activities of tea infusions made from different kinds of Zijuan tea products were determined by measuring their DPPH radical scavenging capacity, ABTS radical scavenging capacity, ferric reducing antioxidant power (FRAP), and cellular antioxidant activity (CAA). Generally Zijuan green tea has stronger antioxidant activity than Zijuan Oolong tea and Zijuan black tea. Moreover, a significant positive correlation was observed between the total anthocyanins and antioxidant activity as measured by DPPH. (r = 0.896), ABTS.+ (r = 0.933), FRAP (r = 0.907) and CAA (r = 0.967) assays, suggesting that anthocyanins contribute greatly to the antioxidant activity of Zijuan tea products. This study provides a foundation for further basic research of anthocyanins and the exploitation of the health benefits of natural anthocyanins in Zijuan tea cultivar.