Figure 2.15 The structures of procyanidins B3 and B6.
phenolic acids and procyanidins. The phenolic acids are either derivatives of benzoic acid, such as p-hydroxybenzoic acid, procatechuic acid, vanillic acid or gallic acid, or cinnamic acid derivatives such as p-coumaric acid, caffeic acid and ferulic acid. These acids exist in the free form and as glucosides and glucose esters. The procyanidins are polymers of catechin or epicatechin monomers, composed of 2-12 monomers. The major dimers include procyanidin B1, consisting of catechin and epicatechin, followed by B3, consisting of two catechin monomers linked by a C4-C8 bond, and lower concentrations of the
equivalent dimers C4-C6 linked, namely B6 and B7. Monomeric catechin, free taxifolin and its glucoside, and vanillin have also been found.48 The structures of two proanthocyanidins found in Pycnogenol are shown in Figure 2.15.
Metabolites of procyanidins (see Table 4.1) were identified after oral intake by humans, and maximum excretion was seen after between 8 and 15 hours, indicating slow absorption and metabolism.49
Legal classification: No restriction Recommended dose: 25-200 mg/day Formulations available: Capsule
Resveratrol (Figure 2.16) has been identified in the leaves, skins and petals of Vitis vinifera, and also in wines and grape juice, but is also in other foods, such as peanut butter. In grape products, levels are higher after infection of the vine with Botrytis cinerea, and in red wines manufactured with extended time in contact with the skins.50 In addition to resveratrol, a number of closely related stilbene analogues are also present.
Figure 2.16 The structure of resveratrol. Metabolism and pharmacokinetics
A number of degradation products have been identified (see Table 4.1). After oral administration of 25 mg resveratrol to humans, the highest plasma concentrations were detected after 30 minutes, which returned
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