A-type proanthocyanidin
A type proanthocyanidins are a specific type of proanthocyanidins, which are a class of flavonoid. Proanthocyanidins fall under a wide range of names in the nutritional and scientific vernacular, including oligomeric proanthocyanidins, flavonoids, polyphenols, condensed tannins, and OPCs. Proanthocyanidins were first popularized by French scientist Jacques Masquelier.
A-type linkage is a less common feature in proanthocyanidins with both 4β→8 and 2β→O→7 interflavanoid bonds.
A-type proanthocyanidin glycosides can be isolated from cocoa liquor.
Dimers
Other A-type proanthocyanidins can be found in cranberries, cinnamon, peanut skins and Geranium niveum.
Chemistry
B-type procyanidins can be converted to A-type procyanidins by radical oxidation. Fragmentation patterns for A-type proanthocyanidins include heterocyclic ring fission, retro-Diels-Alder fission, benzofuran-forming fission and quinone methide fission.
Metabolism
The metabolism of type-A proanthocyanidins is significant since a large number of metabolites are detected in urine and feces soon after ingestion of foods rich in polymers, indicating rapid elimination and absence of physiological effect. Polymeric type-A proanthocyanidins are depolymerized into epicatechin units in the small intestine, then cleaved into smaller phenolic acids with no known biological role.
Research
In vitro, A-type proanthocyanidins isolated from cranberry juice cocktail demonstrated anti-adhesion activity against E. coli binding to urinary tract epithelial cells, whereas B-type proanthocyanidins from grape exhibited minor activity. In humans, a 2014 review indicated there was insufficient clinical evidence that cranberry type-A proanthocyanidins are effective in lowering the risk of urinary tract infections, while a 2023 review concluded that long-term consumption of cranberry products may reduce the risk of UTIs in certain groups.