Determination of polyphenol antioxidants in the samples of green tea. The characteristic chromatographic profiles

The conditions for the selective separation of polyphenols and caffeine with reverse-phase high-performance liquid chromatography with diodarray ( RP HPLC-DAD ) and mass-spectrometric detections ( RP HPLC/MS ) were found. Using the developed technique, chromatographic profiles of 29 samples of green tea (including 11 selection ones provided by the All-Russian Research Institute of Floriculture and Subtropical Crops, Sochi) were obtained. Using HPLC/MS, two unknown analytes (catechin gallate and gallocatechin gallate) of the tea samples were identified. Chemometric processing of the characteristic profiles of polyphenols by the principal component analysis ( PCA ) was accomplished. On the scores plot for the first and second principal components, there is a separation of data into two clusters (selection and Greenfield teas) relative to the first principal component ( PC-1 ). Analysis of the PC-1 loadings plot revealed the dominant analytes (gallic acid, gallocatechin, caffeine, epigallocatechin gallate and epicatechin gallate), which determine the differences between green teas samples. PCA-model separately for the profiles only selections teas was built. Analysis of the plot of scores relative to the first two principal components made it possible to detect the dependence of the concentration of polyphenols and caffeine in selections tea leafs on harvest season. A possible correlation has been established between PC-2 and harvest time, but this requires further research.