Category:FLT
Proanthocyanidin, Condensed Tannin
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Upper classes : FL Flavonoid
Overview
Proanthocyanidin, or condensed (meaning not-hydrolyzable) tannin, is a polymer of flavan-3-ols. Type B is formed from (epi)catechins connected by C4-C6 bond or C4-C8 bond. Type A contains an additional ether bond between C2 and C7. Depending on the unit types, different names may be used.
- procyanidins ... polymer of (epi)catechins
- propelargonidins ... polymer of (epi)afzelechins
- prodelphinidins ... polymer of (epi)gallocatechins
About catechins
Catechins refer to a subgroup of flavan 3-ol derivatives (FL63AC). The two chiral center at C2 and C3 of the flavan 3-ols produces 4 isomers, and (+)-Catechin and its stereoisomer (-)-Epicatechin are naturally abundant. Less abundant are (-)-Catechin and (+)-Epicatechin.
- afzelechin ... catechin minus 1 hydroxyl group in ring B
- gallocatechin ... catechin plus 1 hydroxyl group in ring B
| Structure | 
|
|
|
|
|---|---|---|---|---|
| Name | (+)-Catechin or D-Catechin |
(-)-Epicatechin or L-Epicatechin |
ent-Catechin or (-)-Catechin |
ent-Epicatechin or (+)-Epicatechin |
| B-ring stereo | ↓ | ↓ | ↑ | ↑ |
| 3-Hydroxyl stereo | ↑ | ↓ | ↓ | ↑ |
| Afzelechins | (+)-Afzelechin | (-)-Epiafzelechin | ent-Epiafzelechin | |
| Gallocatechins | (+)-Gallocatechin | (-)-Epigallocatechin | ent-Gallocatechin |
Among the stereoisomers, the bioavailability in human follows the order:
| (-)-epicatechin | > | (+)-catechin | = | (+)-epicatechin | > | (-)-catechin |
The circulation level of (-)-epicatechin is 6 times higher than that of (-)-catechin. Naturally abundant species are more bioavailable than less abundant ones.
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