Oligomeric proanthocyanidins – Food sources and health benefits

Proanthocyanidins are condensed tannins with various pharmacological properties. The compound forms a unique class of high-molecular weight oligomeric and polymeric secondary metabolites. Proanthocyanidins are present in flowers, nuts, fruits, bark, and seeds of various plants, as a defense against biotic and abiotic stressors. Their astringency protects the plants from pathogens and predators.

Proanthocyanidin degree of polymerization can range between 3 and 11. Usually, proanthocyanidins with a lower degree of polymerization (two to four monomers) are named oligomeric proanthocyanidins, whereas those with more than five monomers are called polymeric proanthocyanidins.

Oligomeric proanthocyanidins are one of the commonest bioflavonoids with a special molecular structure, formed by oligomerization or polymerization of subunits catechin, epicatechin, and their gallic acid esters primarily known for their excellent antioxidant activity.

Cocoa beans are a well-known source of antioxidant polyphenols. Especially individual oligomeric proanthocyanidins demonstrated a significant contribution to the total antioxidant activity of cocoa compared to monomeric compounds.

Chocolate contains flavonoids not found in tea, with high concentrations of oligomeric procyanidins. Grape seed and pine bark extracts are also rich with oligomeric proanthocyanidins. Oligomeric proanthocyanidins are also abundant in blackjack oak, horse chestnut, witch hazel and hawthorn, as well as in apples, berries, barley (and beer made from it), bean hulls, chocolate, rhubarb, rose hips and sorghum.

Proanthocyanidins are shown to be highly effective inhibitors of radical chain reactions. In cocoa, they consist of oligomers or polymers of (+)- catechin and/or (-)-epicatechin units. The size of proanthocyanidins is specified by their degree of polymerization (DP).

Oligomeric proanthocyanidins are primarily known for their antioxidant activity. It is widely reported that Oligomeric proanthocyanidin could prevent oxidative damage in tissues by reducing lipid oxidation and/or inhibit production of free radicals.

Oligomeric proanthocyanidin complexes also have been reported to demonstrate, antibacterial, antiviral, anticarcinogenic, anti-inflammatory, anti-allergic, and vasodilatory actions. In addition, they have been found to inhibit lipid peroxidation, platelet aggregation, capillary permeability and fragility, and to affect enzyme systems including phospholipase A2, cyclooxygenase, and lipoxygenase.
Oligomeric proanthocyanidins – Food sources and health benefits