Catechin /ˈkætɪtʃɪn/ is a flavan-3-ol, a type of natural phenol and antioxidant. It is a plant secondary metabolite. It belongs to the group of flavan-3-ols (or simply flavanols), part of the chemical family of flavonoids.(+)-catechin (2R,3S)(-)-catechin (2S,3R)(-)-epicatechin (2R,3R)(+)-epicatechin (2S,3S)(500 MHz, CD3OD): Referenced : doublet, dd : doublet of doublets,m : multiplet, s : singlet2.49 (1H, dd, J = 16.0, 8.6 Hz, H-4a),2.82 (1H, dd, J = 16.0, 1.6 Hz, H-4b), 3.97 (1H, m, H-3), 4.56 (1H, d, J = 7.8 Hz, H-2),5.86 (1H, d, J = 2.1 Hz, H-6), 5.92 (1H, d, J = 2.1 Hz, H-8), 6.70 (1H, dd, J = 8.1, 1.8 Hz, H-6'), 6.75 (1H, d, J = 8.1 Hz, H-5'), 6.83 (1H, d, J = 1.8 Hz, H-2')273 water loss139 Retro Diels Alder123165147 Catechin /ˈkætɪtʃɪn/ is a flavan-3-ol, a type of natural phenol and antioxidant. It is a plant secondary metabolite. It belongs to the group of flavan-3-ols (or simply flavanols), part of the chemical family of flavonoids. The name of the catechin chemical family derives from catechu, which is the tannic juice or boiled extract of Mimosa catechu (Acacia catechu L.f). Catechin possesses two benzene rings (called the A- and B-rings) and a dihydropyran heterocycle (the C-ring) with a hydroxyl group on carbon 3. The A ring is similar to a resorcinol moiety while the B ring is similar to a catechol moiety. There are two chiral centers on the molecule on carbons 2 and 3. Therefore, it has four diastereoisomers. Two of the isomers are in trans configuration and are called catechin and the other two are in cis configuration and are called epicatechin. The most common catechin isomer is the (+)-catechin. The other stereoisomer is (-)-catechin or ent-catechin. The most common epicatechin isomer is (-)-epicatechin (also known under the names L-epicatechin, epicatechol, (-)-epicatechol, l-acacatechin, l-epicatechol, epi-catechin, 2,3-cis-epicatechin or (2R,3R)-(-)-epicatechin). The different epimers can be distinguished using chiral column chromatography.