A-type pro-anthocyanidins

Pro-anthocyanidins, also called condensed tannins, are oligomers and polymers of monomeric flavonoids. Pro-anthocyanidins are present in flowers, nuts, fruits, bark, and seeds of various plants, as a defense against biotic and abiotic stressors.

Pro-anthocyanidins can be differentiated into B-type or A-type depending on their interflavanic linkages.

A-type pro-anthocyanidins containing double interflavanyl linkages (for example, procyanidin A2: epicatechin (2b→7,4b→8)-epicatechin) compared to B-type pro-anthocyanidins that have a single interflavanyl bond, typically between C4→C8 (for example procyanidin B2: epicatechin–(4b→8)-epicatechin.

The most common A-type compounds are A1 and A2. A-type pro-anthocyanidins were found in only three fruits (cranberry, avocado and plum), one nut (peanut), and two spices (cinnamon and curry).

Study shows that cinnamon, which contains a series of unique trimeric and tetrameric procyanidins with A-type linkages, significantly decreased plasma levels of triglycerides and total and LDL cholesterol, when administered (1–6 g=day) just for 20 days.

Pro-anthocyanidins found in cranberry juice with A-type linkages prevented adhesion of uropathogenic P-fimbriated E. coli suggesting they may help to maintain a healthy urinary tract.
A-type pro-anthocyanidins

What is anthocyanidin?

When the sugar moiety of an anthocyanin is hydrolyzed, the aglycone (non-sugar hydrolysis product) is referred to as an anthocyanidin.

The color of anthocyanins and anthocyanidins results from excitation of molecule by visible light. At pH values lower than 3, the anthocyanidin appears as the red flavylium cation, and at pH values higher than 6 it is preset as the blue quinonoidal base form.

The richest sources of anthocyanidins to the diet are red wine and fruit, particularly berries. Foods can have one or a variety of anthocyanidins and the concentration is influenced by environmental conditions, ripeness, cultivar, cultivation site, processing and storage.

Only three types of anthocyanidins have been identified in plant tissues. Pelargonidin, cyanidin and delphinidin are wide spread in nature with cyanidin the most common.

Cyanidin is the anthocyanidin found in red cabbage, pelargonidin occurs in radishes and red-seeded varieties of bean and delphinidin occurs in aubergines.

Anthocyanidins are less water soluble than their corresponding glycosides (anthocyanins) and they are not found free in nature.

Freezing may be the best method of preserving anthocyanidins in foods so as the consumption can continue throughout the year even when particular foods such as berries are not in season.
What is anthocyanidin?