Thearubigin

About: Thearubigin is a research topic. Over the lifetime, 178 publications have been published within this topic receiving 7034 citations.

Tea catechins and polyphenols: health effects, metabolism, and antioxidant functions.

Abstract: Increasing interest in the health benefits of tea has led to the inclusion of tea extracts in dietary supplements and functional foods. However, epidemiologic evidence regarding the effects of tea consumption on cancer and cardiovascular disease risk is conflicting. While tea contains a number of bioactive chemicals, it is particularly rich in catechins, of which epigallocatechin gallate (EGCG) is the most abundant. Catechins and their derivatives are thought to contribute to the beneficial effects ascribed to tea. Tea catechins and polyphenols are effective scavengers of reactive oxygen species in vitro and may also function indirectly as antioxidants through their effects on transcription factors and enzyme activities. The fact that catechins are rapidly and extensively metabolized emphasizes the importance of demonstrating their antioxidant activity in vivo. In humans, modest transient increases in plasma antioxidant capacity have been demonstrated following the consumption of tea and green tea catechins. The effects of tea and green tea catechins on biomarkers of oxidative stress, especially oxidative DNA damage, appear very promising in animal models, but data on biomarkers of in vivo oxidative stress in humans are limited. Larger human studies examining the effects of tea and tea catechin intake on biomarkers of oxidative damage to lipids, proteins, and DNA are needed.

Flavanol composition and caffeine content of green leaf as quality potential indicators of Kenyan black teas

Abstract: The flavanol composition and caffeine content of green tea leaf, black tea quality parameters of theaflavins, thearubigins, liquor brightness and total colour varied more among clones than with time of the year In green leaf, either (-)epicatechin gallate or (-)epigallocatechin gallate was the dominant flavanol present Regression analysis of tasters' preferences for black teas against green leaf chemical components showed positive and significant correlations for (-)epicatechin gallate (r = 0·498, P ⩽ 0·05 for taster A; r = 0·665, P ⩽ 0·01 for taster B, and r = 0·678, P ⩽ 0·01 for both tasters' overall ranking), (-)epigallocatechin gallate (r = 0·513, P ⩽ 0·05 for taster B; r = 0·532, P ⩽ 0·05 for both tasters' overall ranking and caffeine (r = 0·523, P ⩽ 0·05 for taster A; r = 0·657, P ⩽ 0·01 for taster B; and r = 0·686, P ⩽ 0·01 for both tasters' overall ranking) Similar regressions against black tea theaflavins, thearubigin content, liquor brightness and total colour were not significant The results suggest that the green leaf chemical components, (-)epicatechin gallate, (-)epigallocatechin gallate and caffeine could be used as quality potential indicators during clonal selection and propagation © 1997 SCI

Role of polyphenol oxidase and peroxidase in the generation of black tea theaflavins.

Abstract: It has been reported earlier that when macerated tea leaf is fermented at lower pH, the resultant black tea contains increased levels of theaflavin, an important quality marker in black tea. In an attempt to investigate the biochemistry and chemistry underlying this observation, in vitro oxidation experiments using polyphenol oxidase (PPO) from fresh tea leaves, horseradish peroxidase (POD), and tea catechins, precursors for theaflavins, were carried out. In vitro oxidation experiments using crude tea PPO resulted in higher content of theaflavins at pH 4.5 in comparison with pH 5.5, the normal pH of the macerated tea leaf. When purified PPO was used in the in vitro system, surprisingly a reversal of this trend was observed, with more theaflavins being formed at the higher pH. A combination of pure tea PPO and POD led to an observation similar to that with the crude enzyme preparation, suggesting a possible role for POD in the formation or degradation of theaflavin. POD was observed to oxidize theaflavins in the presence of H(2)O(2), leading to the formation of thearubigin, another black tea pigment. This paper demonstrates that tea PPO, while oxidizing catechins, generates H(2)O(2). The amount of H(2)O(2) produced is greater at pH 5.5, the optimum pH for PPO activity, than at pH 4.5. Hence, an observed increase of theaflavins in black teas fermented at pH 4.5 appears to be due to lower turnover of formed theaflavins into thearubigins.