Catechins.

 

Tea catechins are responsible for the astringent taste of green tea. Catechins of green tea leaves are account for about 10 % of dry w eight, including （-）- epigallocatechin gallate（ EGCg）50 %,（-）- epigallocatechin（ EGC）30 %,（-）- epicatechin gallate （ECg）10 % and（-）- epicatechin（EC）10 %. Crystals of catechins are sampled in the photographs on the right. A variety of biological activities are attributed to anti-oxidative, radioprotective, ant-mutagenic, antitumor, anti-hyperglycemic, anti-hypercholesterolemic, fat reducing, anti-ulcer, anti-bacterial, bowel modulating, anti-viral, anti-carious, anti-hypertensive actions and the inhibitory activity of some enzymes.

■ Cancer Chemoprevention: Recently, some review articles have reported the relationship between the tea consumption and the human cancer risk. A general overview of the pertinent epidemiological studies on tea consumption and cancer prevention in different organs such as bladder and urinary tract, breast, colon and rectum, esophagus, kidney, liver, lung, pancreas, stomach, and uterus is provided. These studies indicated that the green tea reduced human cancer risk in some cases. Catechins of tea are bio-antimutagens, and reduced the high spontaneous mutations due to altered DNA-polymerase III in a mutator strain of Bacillus subtilis (see figure left). Because of their antimutagenic activities, the tea catechins show various anti-tumor actions, too. For example, catechins significantly decreased the number and the area of preneoplastic glutathione S - transferase placental positive foci -form in the liver; These results suggest that the tea catechins have a chemopreventive activity against cancer of the liver.

■ Anti-Hypercholesterolemic:Activity In order to prevent cardiovascular diseases such as heart attack or brain stroke, it is very important to keep the cholesterol level in the blood within the normal range. The administration of tea catechins to rats was proved to suppress excessive rise of cholesterol concentration in the blood. As shown in figure right, addition of 1 % catechins to diet also suppressed the rise of total cholesterol concentration and particularly LDL - cholesterol concentration. The results demonstrate that tea catechins exert a hypercholesterolemic effect in cholesterol-fed rats.

 ■ Anti-Hyperglycemic: Activity In our present affluent society, obesity and diabetes are serious problems, both of which are bases of various complicated disorders. In the both diseases, a well-programmed dietary control is crucial. Constantly higher concentrations of glucose in the blood renders the vein wall fragile and causes such various disorders as renal failure, heart attack, stroke, and high blood pressure. Tea catechins exhibit inhibitory behaviors on digestive enzymes such as α- amylase and sucrase. The administration of tea catechins to human was proved to suppress an excessive rise of plasma glucose concentration after starch or sucrose intake.

 ■ Bowel Modulating: Activity Intestinal flora of human is composed of 100 trillion viable bacteria belonged to 100 different species. The condition of the intestinal flora influences many factors pertaining to the host’s health and vise versa. These factors include infection, immune response, cancer aging, physiological function, effect of medicines, nutrition. Significant changes in fecal flora and fecal odorous parameters were noted after administering tea catechins, indicating marked improvement of fecal conditions and the reduction of fecal odors