Simultaneous determination of caffeine and some selected polyphenols in Wuyi Rock tea by high-performance liquid chromatography.

The primary taste and healthy benefits of tea are mainly attributed to tea polyphenols and caffeine. Due to very many kinds of flavonoid glycosides in tea and the lack of commercial standards of flavonoid glycosides, it is critical to develop a rapid and cheap method for determining flavonoid glycosides of tea. Contents of myricetin glycosides and quercetin glycosides in Wuyi Rock tea were determined by detecting contents of corresponding myricetin and quercetin. Optimizing hydrolysis conditions for hydrolyzing flavonoid glycosides to their corresponding flavonols including quercetin and myricetin in Wuyi Rock tea was a key technology for detecting contents of corresponding myricetin and quercetin. The results showed that hydrolysis at 2 mol/L HCl solution and at 90 °C for 1 h was an optimizing condition for hydrolyzing flavonoid glycosides to myricetin and quercetin in Wuyi Rock tea. Caffeine and seven kinds of polyphenols (GA, EGC, C, EGCG, EC, ECG, and CGA) in 20 samples of Wuyi Rock tea were simultaneously determined using a simple and fast reverse-phase high-performance liquid chromatography procedure coupled with photodiode array detector (RP-HPLC-PDAD). The results indicated that there were significant (P < 0.05) differences of ECG, CGA, ECG, and myricetin glycosides in 'Wuyi Rougui' and 'Wuyi Shuixian', which were credited with causing the difference in taste between these two cultivar of Wuyi Rock tea. The study may be useful for clarifying the cause of "cultivated varieties flavor" of Wuyi Rock tea.