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. 2021 Apr 28;10(5):699. doi: 10.3390/antiox10050699

Table 2.

Main extractable phenolic compounds identified in grape seed (GS) and grape skin (GK) meals expressed as mg per 100 g of DM (dry matter).

Phenolic Compounds GS Meal GK Meal
Flavanol monomers Catechin 108.0 ± 5.1 11.6 ± 0.60
Epicatechin 93.5 ± 7.0 9.68 ± 0.73
Epicatechin 3-O-gallate 5.21 ± 0.10 0.71 ± 0.01
Flavanol dimers Procyanidin B1 32.0 ± 1.11 3.81 ± 0.14
Procyanidin B2 32.9 ± 1.14 4.26 ± 0.16
Procyanidin B3 30.2 ± 1.82 1.51 ± 0.29
Procyanidin gallate 1 1 8.72 ± 0.84 3.04 ± 0.15
Procyanidin gallate 2 1 29.4 ± 3.13 4.67 ± 0.32
Flavanol trimers Procyanidin C1 19.7 ± 1.52 2.92 ± 0.23
Procyanidin trimer 2 2 6.99 ± 0.52 1.16 ± 0.09
Procyanidin trimer 3 2 16.7 ± 1.61 2.29 ± 0.23
Procyanidin trimer 4 2 8.43 ± 0.58 1.25 ± 0.09
Flavanol tetramers Procyanidin cinnamtannin A2 25.7 ± 0.69 5.20 ± 0.14
Procyanidin tetramer 3 9.78 ± 0.10 3.55 ± 0.20
Phenolic acids Gallic acid 72.2 ± 5.60 39.1 ± 3.80
Caftaric acid nd 4 25.2 ± 2.50
Fertaric acid nd 14.1 ± 0.50
Coutaric acid nd 9.78 ± 0.30
Total extractable polyphenols, g GAE 5/100 g DM 7.93 ± 0.60 2.35 ± 0.14

1 Compounds identified by prediction of chemical formula from accurate ion mass measurement. Quantified by using the calibration curve of procyanidin B2. 2 Compounds identified by prediction of chemical formula from accurate ion mass measurement. Quantified by using the calibration curve of procyanidin C1. 3 Compounds identified by prediction of chemical formula from accurate ion mass measurement. Quantified by using the calibration curve of cinnamtannin A2. 4 nd: not detected. 5 GAE: gallic acid equivalents.