|
|Section2= |Section3= |Section5= }} Catechin 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) == Chemistry == 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 (2''R'',3''R'')-(-)-epicatechin). The different epimers can be distinguished using chiral column chromatography. Making reference to no particular isomer, the molecule can just be called catechin. Mixtures of the different enantiomers can be called (+/-)-catechin or DL-catechin and (+/-)-epicatechin or DL-epicatechin. File:(+)-Catechin.png|(+)-catechin (2''R'',3''S'') File:(-)-catechin.PNG|(-)-catechin (2''S'',3''R'') File:Epicatechin.png|(-)-Epicatechin (2''R'',3''R'') File:(+)-epicatechin.PNG|(+)-epicatechin (2''S'',3''S'') Moreover, the flexibility of the C-ring allows for two conformation isomers, putting the B ring either in a pseudoequatorial position (E conformer) or in a pseudoaxial position (A conformer). Studies confirmed that (+)-catechin adopts a mixture of A- and E-conformers in aqueous solution and their conformational equilibrium has been evaluated to be 33:67. Regarding the antioxidant activity, (+)-catechin has been found to be the most powerful scavenger between different members of the different classes of flavonoids. The ability to quench singlet oxygen seems to be in relation with the chemical structure of catechin, with the presence of the catechol moiety on ring B and the presence of a hydroxyl group activating the double bond on ring C. Catechin exists in the form of a glycoside. Antioxidant properties can also be provided using a catechin associated with a sugar. In 1975-76, a group of USSR scientists of Kaz ssr discovered first the catechin rhamnoside using the plants of ''Filipendula'' that grow in that region. Pioneer and head of the discovery was PhD N. D. Storozhenko born in 1944. Though not thoroughly studied, the rhamnoside of catechin can enter the blood cell without breaking the outer layer. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Catechin」の詳細全文を読む スポンサード リンク
|