These compounds are abundant in teas derived from the tea-plant Camellia sinensis as well as in some cocoas and chocolates. Catechin and epicatechin are epimers, with (-)-epicatechin and (+)-catechin being the most common optical isomers found in nature. Catechin was first isolated from the plant extract catechu, above, from which it derives its name. Heating catechin past its point of decomposition releases pyrocatechol (also called catechol), which explains the common origin of the names of these compounds. Epigallocatechin and gallocatechin contain an additional phenolic hydroxyl group when compared to epicatechin and catechin, respectively, similar to the difference in pyrogallol compared to pyrocatechol. Catechin gallates are gallic acid esters of the catechins; such as EGCG (epigallocatechin gallate), which is commonly the most abundant catechin in tea.