concept

Oligomeric proanthocyanidins (OPC)

Oligomeric proanthocyanidins (OPC) strictly refer to dimer and trimer polymerizations of catechins. OPCs are found in most plants and thus are common in the human diet. Especially the skin, seeds, and seed coats of purple or red pigmented plants contain large amounts of OPCs.[6] They are dense in grape seeds and skin, and therefore in red wine and grape seed extract, cocoa, nuts and all Prunus fruits (most concentrated in the skin), and in the bark of Cinnamomum (cinnamon)[4] and Pinus pinaster (pine bark; formerly known as Pinus maritima), along with many other pine species. OPCs also can be found in blueberries, cranberries (notably procyanidin A2),[26] aronia,[27] hawthorn, rosehip, and sea buckthorn.[28] Oligomeric proanthocyanidins can be extracted via Vaccinium pahalae from in vitro cell culture.[29] The US Department of Agriculture maintains a database of botanical and food sources of proanthocyanidins.[6] Plant defense In nature, proanthocyanidins serve among other chemical and induced defense mechanisms against plant pathogens and predators, such as occurs in strawberries.[30] Bioavailability Proanthocyanidin has low bioavailability, with 90% remaining unabsorbed from the intestines until metabolized by gut flora to the more bioavailable metabolites.[16] Non-oxidative chemical depolymerisation Condensed tannins can undergo acid-catalyzed cleavage in the presence of (or an excess of) a nucleophile[31] like phloroglucinol (reaction called phloroglucinolysis), benzyl mercaptan (reaction called thiolysis), thioglycolic acid (reaction called thioglycolysis) or cysteamine. Flavan-3-ol compounds used with methanol produce short-chain procyanidin dimers, trimers, or tetramers which are more absorbable.[32] These techniques are generally called depolymerisation and give information such as average degree of polymerisation or percentage of galloylation. These are SN1 reactions, a type of substitution reaction in organic chemistry, involving a carbocation intermediate under strongly acidic conditions in polar protic solvents like methanol. The reaction leads to the formation of free and derived monomers that can be further analyzed or used to enhance procyanidin absorption and bioavailability.[32] The free monomers correspond to the terminal units of the condensed tannins chains. In general, reactions are made in methanol, especially thiolysis, as benzyl mercaptan has a low solubility in water. They involve a moderate (50 to 90 °C) heating for a few minutes. Epimerisation may happen. Phloroglucinolysis can be used for instance for proanthocyanidins characterisation in wine[33] or in the grape seed and skin tissues.[34] Thioglycolysis can be used to study proanthocyanidins[35] or the oxidation of condensed tannins.[36] It is also used for lignin quantitation.[37] Reaction on condensed tannins from Douglas fir bark produces epicatechin and catechin thioglycolates.[38] Condensed tannins from Lithocarpus glaber leaves have been analysed through acid-catalyzed degradation in the presence of cysteamine.[39]

Ref: https://en.wikipedia.org/wiki/Proanthocyanidin#Oligomeric_proanthocyanidins

20 confidence points
0 comments
Added on Jun 26, 2022 by Barbara Van De Keer
Edited on Jun 26, 2022 by No update

Join Ninatoka!!

NinatoKa's goal is to support you as a therapist in unravelling the illness pathway from symptoms to cause, and to help you detect potential interventions.

Go to Explore to start your discovery!

Go to Learn to scroll through newly added data.

Go to Contribute to contribute to the Ninatoka database.

You can rate content up or down and add comments if you agree or disagree.