Proanthocyanidins are mostly polymeric units of catechin and epicatechin. Many are oligomers of catechin and epicatechin and their gallic acid esters. They are oligomeric compounds, formed from catechin and epicatechin molecules. The molecule catechin, another natural compound present in tea, contains a catechol group. Persimmon fruits contain phytochemicals, such as catechin, gallocatechin and betulinic acid. Most data for human metabolism of flavan-3-ols are available for monomeric compounds, especially Catechin. The nanoparticles would clump together without the catechin coating. He proved the presence of catechin in cocoa beans in 1931. Grape seed extracts contain three monomers (catechin, epicatechin and epicatechin gallate) and procyanidin oligomers. It is mainly composed of cattechu-tanic acid (a tannin) and catechin (a flavan-3-ol). Reaction on condensed tannins from Douglas fir bark produces epicatechin and catechin thioglycolates. The most common catechin isomer is the (+)-catechin. Among fungi, degradation of catechin can be achieved by "Chaetomium cupreum". This was a thermal decomposition product of the flavanols in catechin. An example of such molecules is catechin.