A type proanthocyanidins are a specific type of

proanthocyanidin Proanthocyanidins are a class of polyphenols found in many plants, such as cranberry, blueberry, and grape seeds. Chemically, they are oligomeric flavonoids. Many are oligomers of catechin and epicatechin and their gallic acid esters. More complex ...

s, which are a class of

flavonoid Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids ...

. Proanthocyanidins fall under a wide range of names in the nutritional and scientific vernacular, including

oligomer In chemistry and biochemistry, an oligomer () is a molecule that consists of a few repeating units which could be derived, actually or conceptually, from smaller molecules, monomers.Quote: ''Oligomer molecule: A molecule of intermediate relativ ...

ic proanthocyanidins, flavonoids,

polyphenol Polyphenols () are a large family of naturally occurring phenols. They are abundant in plants and structurally diverse. Polyphenols include phenolic acids, flavonoids, tannic acid, and ellagitannin, some of which have been used historically as ...

condensed tannin Condensed tannins (proanthocyanidins, polyflavonoid tannins, catechol-type tannins, pyrocatecollic type tannins, non-hydrolyzable tannins or flavolans) are polymers formed by the condensation of flavans. They do not contain sugar residues. They ...

s, and OPCs. Proanthocyanidins were first popularized by French scientist Jacques Masquelier.

Distribution in plants

A-type linkage is a less common feature in proanthocyanidins with both 4β→8 ( B-type) and 2β→O→7 interflavanoid bonds. A-type proanthocyanidin

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

s can be isolated from cocoa liquor.

Dimers

* Procyanidin A1 is an epicatechin-(2β→7,4β→8)-catechin dimer. * Procyanidin A2 is a dimeric (-)epicatechin. Other A-type proanthocyanidins can be found in cranberries,

cinnamon Cinnamon is a spice obtained from the inner bark of several tree species from the genus ''Cinnamomum''. Cinnamon is used mainly as an aromatic condiment and flavouring additive in a wide variety of cuisines, sweet and savoury dishes, biscuits, b ...

, peanut skins and ''

Geranium niveum ''Geranium niveum'' is a plant species in the genus ''Geranium''. It is a medicinal herb widely used by the Tarahumara Indians of Mexico. Geranin A Geranin A is an A type proanthocyanidin of the propelargonidin sub type. Its structure is ep ...

''.

Chemistry

B-type procyanidins (

catechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from ''catechu'', which is the tannic ...

dimers) can be converted to A-type procyanidins by radical oxidation. Fragmentation patterns for A-type proanthocyanidins include heterocyclic ring fission (HRF), retro-Diels-Alder (RDA) fission, benzofuran-forming fission (BFF) and quinone methide fission (QM).

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 Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

effect. Polymeric type-A proanthocyanidins are depolymerized into

epicatechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from '' catechu'', which is the tann ...

units in the

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

, then cleaved into smaller phenolic acids with no known biological role.

Research

''In vitro'', A-type proanthocyanidins isolated from

cranberry juice Cranberry juice is the liquid juice of the cranberry a fruit recognized for its bright red color, tart taste, and versatility for product manufacturing. Major cranberry products include cranberry juice, dried cranberry, cranberry sauce, frozen ...

cocktail A cocktail is a mixed drink, usually alcoholic beverage, alcoholic. Most commonly, a cocktail is a combination of one or more liquor, spirits mixed with other ingredients, such as juices, flavored syrups, tonic water, Shrub (drink), shrubs, and ...

demonstrated anti-adhesion activity against ''

E. coli ''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escherichia'' that is commonly foun ...

'' binding to

urinary tract The human urinary system, also known as the urinary tract or renal system, consists of the kidneys, ureters, bladder, and the urethra. The purpose of the urinary system is to eliminate waste from the body, regulate blood volume and blood pressu ...

epithelial cells Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

, 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 infection A urinary tract infection (UTI) is an infection that affects a part of the urinary tract. Lower urinary tract infections may involve the bladder (cystitis) or urethra (urethritis) while upper urinary tract infections affect the kidney (pyel ...

s (UTIs), while a 2023 review concluded that long-term consumption of cranberry products may reduce the risk of UTIs in certain groups.

References

{{DEFAULTSORT:A Type Proanthocyanidin Condensed tannins