Composition and biological potential of grape and wine phenolic compounds

Abstract

Polyphenols are common in human diets, primarily in plant-derived food and beverages. They influence multiple sensory properties such as aroma, flavour, colour, and taste, such as astringency and bitterness [1]. The major phenolic compounds in grapes and wines are anthocyanins and tannins (proanthocyanidins or condensed tannins). Tannins are water-soluble phenolic compounds with a molecular weight of 500–3000 Da that can precipitate alkaloids, gelatine, and other proteins. Proanthocyanidins form a considerable portion of the tannins found in wine and in particular contribute heavily to the colour and flavour of red wines. Proanthocyanidins are high-molecular-weight polymers formed from flavan-3-ol monomeric units. Several oligomers, dimers, trimers, tetramers, and pentamers, exist. Tetramers or greater of these flavonols are known as polymeric proanthocyanidins and the astringency of the molecule increases with size. Oligomeric proanthocyanidins are less astringent, bind less strongly to proteins, and are more soluble [2]. A new subfamily of condensed tannin with an unusual skeleton, named crown procyanidins, have been reported [3]. Furthermore, the sensation of astringency caused by tannins is a direct function of their mDP and galloylation percentage [4]. Anthocyanins are glucoside of anthocyanidins. Anthocyanins are differentiated by the degree of hydroxylation and methylation, and also by the nature of the Oses bound to the molecule. Anthocyanidin is the chromophore moiety of the pigment. Acetylglucoside and cinnamoylglucoside anthocyanins have lower perception thresholds than the glucoside fraction at concentrations found in wines [5]. Descriptors associated with these fractions were bitterness and astringency. Anthocyanins also make a sensory contribution to the perception of wine, correlated with the acetylation of molecules. The presence of C-glucosidic ellagitannins in wines and spirits is due to their presence in wood species such as Quercus petraea, Q. robur and Q. alba. The main C-glucosidic ellagitannins extracted by wines during ageing in oak barrels are continuously transformed through condensation, hydrolysis, and oxidation reactions. Phenolic compounds are known to have health benefits, such as a chemopreventive role toward cardiovascular, cancer, and degenerative diseases, as well as pathologies with inflammation. Therefore, wine and grape pomace constitute an abundant source of a wide range of polyphenols, and are sources of antioxidants for nutrition and health.

References

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[4] Ma W., Pierre Waffo-Teguo P., Jourdes M., Li H.,Teissedre P.L.  PLoS One, 2016 Aug 12;11(8):e0161095. doi: 10.1371/journal.pone.0161095. eCollection 2016.

[5] Paissoni M.A.; Waffo-Teguo P.; Ma W.; Jourdes M.; Rolle L.; Teissedre P.L.; (2018) Scientific Reports DOI: 10.1038/s41598-018-35355-x, Vol.8(1) 7098