Determination of Polyphenol and EGCG in Tea and Tea Products by UV-VIS and HPLC Methods

Tea and tea products have been known and used for long and became a tradional culture in many countries in the world, including Vietnam. The quality of tea depends on the concentrations of typical active substances such as polyphenol groups and their active substances (EGCG, ECG, catechin,…). Therefore, study of analytical methods to determine these active substances is necessary to evaluate the quality of tea and tea products. In this study, UV-Vis method was selected to determine total polyphenol and HPLC method was selected to determine the main active ingredient of polyphenol group EGCG. The limit of detections are 0.12 mg/g and 0.064 mg/g for total polyphenol and EGCG, respectively. These methods were applied to determine the concentrations of total phenol and EGCG in 10 samples of tea and tea products. Results show that the concentrations of total phenol and EGCG vary significantly among samples, but there is a certain relationship between the concentration of total phenol and EGCG in each sample.