Procyanidin C2 is a

B type proanthocyanidin B type proanthocyanidins are a specific type of proanthocyanidin, which are a class of flavanoids. They are oligomers of flavan-3-ols. Dimeric B type proanthocyanidins These molecules have the molecular formula C30H26O12 (molar mass : 578.52 g/m ...

trimer, a type of

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 ...

Natural occurrences

Procyanidin C2 is found in grape seeds (''Vitis vinifera'') and

wine Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are m ...

, in

barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...

(''Hordeum vulgare''),

malt Malt is germinated cereal grain that has been dried in a process known as " malting". The grain is made to germinate by soaking in water and is then halted from germinating further by drying with hot air. Malted grain is used to make beer, wh ...

and

beer Beer is one of the oldest and the most widely consumed type of alcoholic drink in the world, and the third most popular drink overall after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from ce ...

, in ''

Betula A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 3 ...

spp.'', in ''

Pinus radiata ''Pinus radiata'' ( syn. ''Pinus insignis''), the Monterey pine, insignis pine or radiata pine, is a species of pine native to the Central Coast of California and Mexico (Guadalupe Island and Cedros island). It is an evergreen conifer in the fa ...

'', in '' Potentilla viscosa'', in ''

Salix caprea ''Salix caprea'', known as goat willow, pussy willow or great sallow, is a common species of willow native to Europe and western and central Asia.Meikle, R. D. (1984). ''Willows and Poplars of Great Britain and Ireland''. BSBI Handbook 4. . Des ...

'' or in ''

Cryptomeria japonica ''Cryptomeria'' (literally "hidden parts") is a monotypic genus of conifer in the cypress family Cupressaceae, formerly belonging to the family Taxodiaceae. It includes only one species, ''Cryptomeria japonica'' ( syn. ''Cupressus japonica'' L ...

''. The contents in barley grain of trimeric proanthocyanidins, including procyanidin C2, range from 53 to 151 μg catechin equivalents/g.

Possible health uses

Proanthocyanidin oligomers, extracted from

grape A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus ''Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began perhaps 8,000 years ago, ...

seeds, have been used for the experimental treatment of androgenic alopecia. When applied topically, they promote hair growth ''in vitro'', and induce anagen ''in vivo''. Procyanidin C2 is the subtype of extract most effective. Experiments showed that both procyanidin C2 and Pycnogenol (French maritime pine bark extract) increase

TNF-α Tumor necrosis factor (TNF, cachexin, or cachectin; formerly known as tumor necrosis factor alpha or TNF-α) is an adipokine and a cytokine. TNF is a member of the TNF superfamily, which consists of various transmembrane proteins with a homolog ...

secretion in a concentration- and time-dependent manner. These results demonstrate that procyanidins act as modulators of the immune response in macrophages.

Chemistry

In the presence of procyanidin C2, the red color of the anthocyanin

oenin Oenin is an anthocyanin. It is the 3-glucoside of malvidin. It is one of the red pigments found in the skin of purple grapes and in wine. Color stabilization of malvidin 3-glucoside at a higher pH can be explained by self-aggregation of the flav ...

appears more stable. However, the HPLC chromatogram shows a decrease in the amplitude of the peaks of oenin and procyanidin C2. Concomitantly, a new peak appears with a maximal absorption in the red region. This newly formed pigment probably comes from the condensation of oenin and procyanidin C2.

Chemical synthesis

A stereoselective synthesis of benzylated catechin trimer under intermolecular condensation is achieved using equimolar amount of dimeric catechin nucleophile and monomeric catechin electrophile catalyzed by AgOTf or AgBF₄. The coupled product can be transformed into procyanidin C2 by a known procedure. The stereoselective synthesis of seven benzylated proanthocyanidin trimers (epicatechin-(4β-8)-epicatechin-(4β-8)-epicatechin trimer (

procyanidin C1 Procyanidin C1 (PCC1) is a B type proanthocyanidin. It is an epicatechin trimer found in grape (''Vitis vinifera''), unripe apples, and cinnamon. Natural occurrence and function Procyanidin C1 can be isolated from grape seed extract. Chemical ...

), catechin-(4α-8)-catechin-(4α-8)-catechin trimer (procyanidin C2), epicatechin-(4β-8)-epicatechin-(4β-8)-catechin trimer and epicatechin-(4β-8)-catechin-(4α-8)-epicatechin trimer derivatives) can be achieved with

TMSOTf Trimethylsilyl trifluoromethanesulfonate is a trifluoromethanesulfonate derivate with a trimethylsilyl R-group. It has similar reactivity to trimethylsilyl chloride, and is also used often in organic synthesis. Illustrative reactions A common ap ...

-catalyzed condensation reaction, in excellent yields. The structure of benzylated procyanidin C2 was confirmed by comparing the 1H NMR spectra of protected procyanidin C2 that was synthesized by two different condensation approaches. Finally, deprotection of (+)-catechin and (−)-epicatechin trimers derivatives gives four natural procyanidin trimers in good yields. Molar equivalents of synthetic (2R,3S,4R or S)-

leucocyanidin Leucocyanidin is a colorless chemical compound that is a member of the class of natural products known as leucoanthocyanidins. Chemistry (+)-Leucocyanidin can be synthesized from (+)-dihydroquercetin by reduction with sodium borohydride. Mola ...

and (+)-

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 ...

condense with exceptional rapidity at pH 5 under ambient conditions to give the all-trans- ,8 and ,6bi- +)-catechins( procyanidins B3, B6) the all-trans- ,8:4,8 and ,8:4,6tri- +)-catechins(procyanidin C2 and isomer).

Iterative oligomer chemical synthesis

A coupling utilising a C8-

boronic acid A boronic acid is an organic compound related to boric acid () in which one of the three hydroxyl groups () is replaced by an alkyl or aryl group (represented by R in the general formula ). As a compound containing a carbon–boron bond, membe ...

as a directing group was developed in the synthesis of natural

procyanidin B3 Procyanidin B3 is a B type proanthocyanidin. Procyanidin B3 is a catechin dimer (catechin-(4α→8)-catechin). Natural occurrences It can be found in red wine, in barley, in beer, in peach or in '' Jatropha macrantha'', the Huanarpo Macho. H ...

(i.e., 3,4-trans-(+)-catechin-4α→8-(+)-catechin dimer). The key interflavan bond is forged using a

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

-promoted coupling of C4-ether with C8-boronic acid to provide the α-linked dimer with high diastereoselectivity. Through the use of a boron

protecting group A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In many ...

, the coupling procedure can be extended to the synthesis of a protected procyanidin trimer analogous to natural procyanidin C2.

References

External links

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knapsack
{{procyanidin Procyanidins Natural phenol trimers