Stability of tea theaflavins and catechins

Green tea catechins (GTC) and theaflavins (TF) possess a variety of biological activities. The present study focused on stability of GTC and TF in various solutions and drinks. It was observed that both GTC and TF were vulnerable to degradation caused by elevation of temperature and pH of incubation media. In general, GTC was more stable than TF. When boiled in water, four GTCs showed similar rates of degradation, but in sodium phosphate buffer (pH7.4) at room temperature, four GTCs demonstrated varying stability, with epigallocatechin gallate (EGCG) and epigallocatechin (EGC) being completely degraded in 6 h of incubation, while epicatechin (EC) and epicatechin gallate (ECG) were only degraded by less than 35%. Four TFs also demonstrated varying stability, with theaflavin-3,3'-digallate (TF3) and theaflavin-3'-gallate- B (TF2B) in general being more stable than theaflavin-1 (TF1) and theaflavin-3-gallate-A (TF2A) in either boiling water or alkaline sodium phosphate buffer. When incubated in various solutions and soft drinks, both GTC and TF had poor long-term stability and decayed by at least 50% during the first month of storage at room temperature. (C) 2003 Elsevier Ltd. All rights reserved.