ANTI-OXIDATIVE EFFECT

Most of the living things on earth, including human beings, need oxygen to stay alive. Sometimes oxygen with extra reaction and related materials are produced in the procedure. They are active oxygen and free-radicals, which cause abnormal oxidation of components such as lipid, protein, and DNA, to depress their functions or kill their cells. Active oxygen kills bacteria and viruses inside body and plays an important role in protecting the body, but it can cause or aggravate diseases like cancer because it attacks all bacteria and body components without specifying certain objects when over-produced or overstocked in body. Our bodies carry anti-oxidative materials that control the production and extinction of active oxygen and free-radicals to prevent irregular functions of cells by excessive oxidation. This is called anti-oxidative action. Vitamin C, E, B-caronene are significant antioxidant vitamins for blood and organs. Plants have polyphenol called flavonoids in them but we humans need to intake antioxidant vitamins with various foods. Flavonoids in tea are one of catechines, and account for 10-15% of dried tea leaves. A catechin, epigallocatechin gallate,(EGCg), is the most among them and is not contained in most of the vegetables but tea(Fig.1). Antioxidative effect of EGCg is one of the strongest among plant polyphenol. Other than catechins, green tea has vitamins, amino acids, and trace metal elements. Fig.2 is the comparison of antioxidant vitamins in green tea and other foods. More VC, VE, and B-carotene are contained in green tea than in spinach, carrots, and cabbage. However, Maccha should be taken, not Sencha, to intake lipid soluble matters such as VE and B-carotene. Green tea has much of antioxidant vitamins, while oolong tea and black tea have less because of more fermentation. Therefore, green tea is the reservoir of antioxidant matters.

(Mitsuaki Sano)