HPLC-DAD-ESI-MS/MS analysis of polyphenols and purine alkaloids in leaves of 22 tea cultivars in China

Using the HPLC-DAD-ESI-MS/MS method, polyphenols and purine alkaloids were analyzed in young leaves of 22 tea cultivars mainly for making oolong tea in China. Ultrasonic extraction in acetonitrile–water (1:1, v/v) was chosen for the preparation of samples for HPLC analysis. Separations were performed on an ODS column with linear gradient elution by the mobile phase consisting of acetonitrile and 1% formic acid aqueous solution. Compared with the standards and data in the literature, 11 catechins, two purine alkaloids, and three non-catechin type of polyphenols were identified, including (−)-epigallocatechin-3-(3″-O-methyl) gallate, (−)-epigallocatechin-3,5-digallate, (−)-epicatechin-3-(3″-O-methyl) gallate, and (−)-epicatechin-3,5-digallate, which are not common catechins in all tea leaves. The contents of the major components, nine catechins and two purine alkaloids were quantified by the HPLC method which were fully validated. The composition of catechins in the leaves of Fujian and Taiwan cultivars group was similar, while the contents of gallated catechins were higher in Guangdong cultivars group than in Fujian and Taiwan cultivars group.