兒茶素主要分為四種：表兒茶酚（epicatechin EC）、表沒食子兒茶酚（epigallocatechin EGC）、表兒茶酚沒食子酸（epicatechin gallate ECg）和表沒食子兒茶酚沒食子酸（epigallocatechin gallate EGCg）。
Sources of catechins
Catechins constitute about 25% of the dry weight of fresh tea leaf, although total catechin content varies widely depending on clonal variation, growing location, seasonal/ 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.
 Health benefits of catechins
The health benefits of catechins have been studied extensively in humans and in animal models. Reduction in atherosclerotic plaques was seen in animal models. Reduction in carcinogenesis was seen in vitro.
Many studies on health benefits have been linked to the catechin content. According to Norman Hollenberg, professor of medicine at Harvard Medical School, epicatechin can reduce the risk of four of the major health problems: stroke, heart failure, cancer and diabetes. He studied the Kuna people in Panama, who drink up to 40 cups of cocoa a week, and found that the prevalence of the "big four" is less than 10%. He believes that epicatechin should be considered essential to the diet and thus classed as a vitamin.Science Daily March 12, 2007
According to one researcher epigallocatechin-3-gallate is an antioxidant that helps protect the skin from UV radiation-induced damage and tumor formation.
Green tea catechins have also been shown to possess antibiotic properties due to their role in disrupting a specific stage of the bacterial DNA replication process.
A study on green-tea catechins is reviewed here: http://www.sciencedaily.com/releases/2007/08/070810194923.htm