Catechins are polyphenols most often found in green tea. They are also present in smaller amounts in black tea, grapes, wine, and chocolate. The catechins in green tea include gallocatechin (GC), epigallocatechin (EGC), epicatechin (EC), and epigallocatechin gallate (EGCG). They are potent antioxidants and are being studied for their beneficial effects on heart health and blood sugar, as well as their cancer-preventive potential.
Graham, H.N. 1992. Green tea composition, consumption and polyphenol chemistry. Prev. Med. 21: 334- 350.