Phenolic content in tea green tea. Catechins constitute about 25% of the dry mass of a fresh tea leaf, although total catechin content varies widely depending on species, clonal variation, growing location, season, light variation, and altitude. They are present in nearly all teas made from "Camellia sinensis", including white tea, green tea, black tea and oolong tea. Of all the catechins in tea, EGCG is the main subject of scientific study with regard to its potential health effects. 4-Hydroxybenzoic acid, 3,4-dihydroxybenzoic acid (protocatechuic acid), 3-methoxy-4-hydroxy-hippuric acid and 3-methoxy-4-hydroxybenzoic acid (vanillic acid) are the main catechins metabolites found in humans after consumption of green
Tea var. "sinensis") may have originated in southern China possibly with hybridization of unknown wild tea relatives. However, since there are no known wild populations of this tea, the precise location of its origin is speculative. Given their genetic differences forming distinct clades, Chinese Assam type tea ("C. sinensis" var. "assamica") may have two different parentages – one being found in southern Yunnan (Xishuangbanna, Pu'er City) and the other in western Yunnan (Lincang, Baoshan). Many types of Southern Yunnan assam tea have been hybridized with the closely related species "Camellia taliensis." Unlike Southern Yunnan Assam tea, Western Yunnan Assam tea shares