Determination of Tea Polyphenols in Bottled Japanese Tea Drinks and Differences in Polyphenol Content in Tea Leaves from Different Variety

Many studies have shown that polyphenols in green tea have antioxidant activity, anti-inflammatory effects, and preventive effects against degenerative diseases, such as cardiovascular diseases and neurodegenerative diseases. We determined nine polyphenols (gallic acid, (−)-gallocatechin, (−)-epigallocatechin, ( + )-catechin (C), (−)-epicatechin (EC), (−)-gallocatechin gallate, (−)-epigallocatechin gallate, (−)-catechin gallate (CG), (−)-epicatechin gallate (ECG)), and caffeine in seven commercially available bottled green-tea drinks by semi-micro HPLC. One of the bottled tea drinks contained a small excess of EC, ECG, C, where C and CG represent heat-epimerized from EC and ECG. We determined the polyphenol contents in different green-tea leaves, and then found that the different contents of EC and ECG in the tea leaves can be attributed to different varieties (Zairaishu and Yabukita). Zairaishu contained notably higher EC, ECG, C, and CG.