Grape seed extract epicatechin

Fig. 2.61. Separation of grape seed extract (a) and grape seed extract spiked with mixture of eight compounds (b) using optimized conditions. Chromatographic conditions are discussed in the text. Peak identification 1 = 2-phenylethanol 2 = vanillin 3 = ferulic acid 4 = protocatechoic acid 5 = caffeic acid 6 = gallic acid 7 = catechin 8 = epicatechin. Reprinted with permission from A. Kamangerpour et al. [167].

The LC/MS does not allow separation and identification of oligomers higher than pentamers because the number of diastereoisomers is large and their separation is not possible. By having positive-ion MALDI-TOF in the reflectron mode, determination of (+)-catechin, (-)-epicatechin oligomers, and their galloylated derivatives up to a heptamer in grape seed extracts as sodium adducts [M+Na]+ is possible... 

It was reported that esterification of (—)-epicatechin and procyanidin B2 by gallic acid can occur and that these gallate esters are only found in the grape seed extract. Grape seed extract contains oligomer procyanidins made up of dimers or trimers of (+)-catechin and (—)-epicatechin.4-6 The procyanidin dimers are comprised of procyanidins Bl, B2, B3, B4, B5, B6, B7, and B8. There are six procyanidin trimers which include procyanidins Cl and C2. 

Grape seeds are rich in polyphenols, especially flavanols (catechin, epicatechin) and gallic acid (Meyer et al., 1997). When grape extracts are prepared after crushing of the seeds, increased levels of phenols are obtained compared with extracts prepared with intact grape seeds. In particular, flavan-3-ol levels increased significantly. The antioxidant activity, as measured by the ability to inhibit LDL oxidation, also increased when the seeds were crushed prior to extraction. 

Table 6.11. Concentrations of different dimeric procyanidins, truner Ci, (—)-monogaUoylated epicatechin (epigal) and catechins [(-l-)-catechin and (—)-epicatechin] in dUnte alcohol extracts from seeds and skins of ripe Merlot and Cabernet Sanvignon grapes (1994). (Results are expressed in mg/1 of eqnivalent (-l-)-catechin) (de Freitas, 1995)...

---