1999 Volume 46 Issue 3 Pages 138-147
Catechins are very important components contained in green tea because of their taste showing astringency and bitterness. In order to make clear the existence of 10 naturally-occurring catechins and four heat-converted catechins (epimeric forms of the catechins) in various kinds of green teas, the qualitative and quantitative studies were conducted by high performance liquid chromatography (HPLC). Preparation method of catechins from green tea leaves for HPLC were as follows : acetone extraction from tea leaves→methyl isobutyl ketone dissolution→methanol dissolution→ODS treatment. In Japanese green teas such as Matcha (powdered green tea or ceremony tea), high quality Sencha (Sencha : a ordinary Japanese green tea), medium Sencha, Bancha (coarse type green tea) and Hojicha (roasted green tea), the sum of four major catechins, i.e. (-)-epigallocatechin-3-gallate, (-)-epicatechin-3-gallate, (-)-epigallocatechin and (-)-epicatechin were dominant in the total catechin contents. In addition, those teas contained the heat-converted catechins, i.e. (-)-gallocatechin-3-gallate, (-)-catechin-3-gallate, (-)-gallocatechin and (-)-catechin in a small amount. A somewhat large amounts of the heat-converted catechins were observed to appear in Hojicha. Chinese green teas such as Lung Ching tea, Yunnan tea and gun powder, Vietnamese green tea and Indian green teas such as Darjeeling green tea and Darjeeling silver tip contained much more total catechin contents and in those (-)-epigallocatechin-3-gallate showed a especially higher content in comparison with the Japanese ones. (-)-Epigallocatechin-3-(3"-O-methyl) gallate, (-)-epicatechin-3-(3"-O-methyl) gallate, (-)-epigallocatechin-3, 5-digallate and (-)-epicatechin-3, 5-digallate were found in Chinese, Vietnamese and Indian green teas. The two catechin-(O-methyl) gallates and the two catechin-digallates were presumably characteristic constituents of China variety (Camellia sinensis var. sinensis) and Assam variety (Camellia sinensis var. assamica), respectively.