Procyanidin BI

Procyanidins in vine shoots consist of partially galloylated units [80]. Thus, two trimeric procyanidins [Ci and epicatechin-(4(3 8)-epicatechin-(4(3- 8)-catechin], six dimeric procyanidins (Bi, B2, B3, B4, B7, and 3 -C>-galloyl-B2), in addition to 3-D-galloyl-(—)-epicatechin, (+)-catechin, and (—)-epicatechin, have been identified in acetone-water and ethyl acetate extracts from vine shoots [90]. 

In a few cases, the synthesis was directed towards well-defined oligomers (dimers, trimers, etc.). The synthesis of bis(5,7,3, 4 -tetra-0-benzyl)-EC 4/1,8-dimer from 5,7,3, 4 -tetra-0-benzyl-EC and 5,7,3, 4 -tetra-0-benzyl-4-(2-hydroxyethoxy)-EC was described by Kozikowski et al. [41]. This compound exhibited the ability to inhibit the growth of several breast cancer cell fines through the induction of cell cycle arrest in the Gq/Gi phase. Analogously, procyanidin-B3, a condensed catechin dimer, has been obtained through condensation of benzylated catechin with various 4-0-alkylated flavan-3,4-diol derivatives in the presence of a Lewis acid. This reaction led to protected procyanidin-B3 and its diastereomer. In particular, octa-O-benzylated procyanidin-B3 has been produced with high levels of stereoselectivity and in excellent isolation yields [42]. 

A considerable effort has also been devoted to the synthesis of C- and, to a lesser extent, " C-labeled catechins and procyanidins. Administration of [U- " C]phenylalanine or [1- " C]acetate to willow tree shoots, led to the isolation of labeled procyanidins B-3 (93), procyanidin B-6 [catechin-(4Q —> 6)-catechin], procyanidin C-2 bis-[catechin-(4Q 8)]-catechin, and a related polymer of high radio-purity. The C-labeled anthocyanins, cyanidin- 3 - 0-/3-D-glucopyranoside, peonidin- 3-0-/3-D-glycopyranoside, and malvidin- 3- 0-/3-D-glucopyranoside, were similarly produced by incorporation of [l- C]phenylalanine into cell suspension cultures of Vitis vinifera Vercauteren and his coworkers made significant contributions by synthesizing r r-4-[ C]catechin, and enantiopure 4-[ C]catechin, 4-[ C]epicatechin, and gram quantities of 4-[ C]procyanidin B-3. ... 

In the case of dimeric procyanidins (Eig-ure 6.25) with a C4-C8 interflavan bond (Bi to B4), oxidation depends on the type of npper structural unit. The oxidizability of the C4-C6 bond (B5 to Bg) originates in the lower structural unit. The presence of (+)-catechin (B3-B4 and Bg-Bv) makes molecnles more oxidizable, as compared to (—)-epicatechin (Bi, B2, Bg, Bg). 

Bv and Bg are absent from the skins. Red and white grape seeds have similar distributions of procyanidins. On the other hand, dimer B2 is in the majority in red grape skins, but practically absent from white grapes, where it is replaced by Bi. These results show that dimeric and trimeric procyanidins, present in very low concentrations, are not the most important phenolic compounds in grapes. 

Bi and Bj) and, recently, trimers (Cj) are commercially available, but dimer Bj and trimer Cj are very expensive. Therefore, the procyanidins, which are not commercially available, were tentatively quantified compared with catechin or epicatechin. As examples, dimer procyanidins were tentatively quantified by using the calibration curve of the dimer B2 [29] or epicatechin [18], and the procyanidins with a degree of polymerization higher than 2 were tentatively quantified by using the calibration curve of catechin [29] or epicatechin [18]. Catechin, epicatechin, and the caffeine and teobromine alkaloids were quantified by using their own calibration curves. 

Contains plant acids (16-18%) composed mainly of r/-tartaric acid (up to ca. 18%), with minor amounts of /-mahc acid. Citric acid has also been reported as a major component in the old literature, though it has not been detected in Indian tamarind (youngken). Other constituents include polyphenolics (catechin, epicatechin, and procyanidin), flavonoids (taxifolin, apigenin, eriodictyol, luteolin, and naringenin), sugars (20-40%), pectin, protein (2.8%), fat, vitamins (e.g., Bi and C), minerals (Ca, K, P, etc.), and tartrate (merck ... 

Prooyanidin Bi dinner Prooyanidin B3 dimer Procyanidin B4 dimer... 

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