Chemical Diversity of Flavan-3-Ols in Grape Seeds: Modulating Factors and Quality Requirements

Abstract

Grape seeds are a rich source of flavan-3-ol monomers, oligomers, and polymers. The diverse profile of compounds includes mainly B-type procyanidins (especially C4→C8 linked molecules) and the key monomers, catechin, and epicatechin that are positively implicated in the ‘French Paradox’. Today grape seed nutraceuticals have become a multi-million-dollar industry. This has created incentives to elucidate the variations in chemistry across cultivars, to identify signs of adulteration, and to understand the intrinsic and extrinsic factors controlling the expression of metabolites in the seeds’ metabolome. This review provides a critical overview of the existing literature on grape seed chemistry. Although the biosynthetic pathways for polymeric procyanidins in seeds have not yet been explained, abiotic factors have been shown to modulate associated genes. Research of extrinsic factors has demonstrated that the control of procyanidin expression is strongly influenced, in order of importance, by genotype (species first, then variety) and environment, as claimed anecdotally. Unfortunately, research outcomes on the effects of abiotic factors have low certainty, because effects can be specific to genotype or variety, and there is limited control over physical metrics in the field. Thus, to gain a fuller understanding of the effects of abiotic factors and biosynthetic pathways, and realise potential for optimisation, a more fundamental research approach is needed. Nevertheless, the current synthesis offers insight into the selection of species or varieties according to the profile of polyphenols, as well as for optimisation of horticultural practices, with a view to produce products that contain the compounds that support health claims.

A Comparative Study of the Influence of Various Fungal-Based Pretreatments of Grape Pomace on Phenolic Compounds Recovery

“…These compounds play an important role in the quality and characteristics of wine and also have the function of a natural preservative. The flavan-3-ols of grape seeds possess various biological effects on human health and contribute to the health properties of wine [ 55 ]. Figure 7 a–d show the dimensionless content of flavan-3-ols (epicatechin gallate, galocatechin gallate) in GP extracts before biological treatment (‘0’ day) and after 1–15 days of biological treatment with eleven filamentous fungi (TV6, TV8, TV AG613, GL, GR, RO, PC, CS, PE, HG and TG).…”

“…Procyanidins are formed by oxidative condensation of (+)-catechin and/or (−)-epicatechin units. Consistently the most abundant procyanidin dimer in grape seeds is procyanidin B2 [ 55 ]. Procyanidins are characterized by antioxidant activity and the ability to specifically bind proteins and regulate cellular signaling pathways.…”

The combined influence of rootstock and vintage climate on the grape and wine flavonoids of Vitis vinifera L. cv. Cabernet Sauvignon in eastern China

“…This difference might be due to the accumulation pattern of flavan-3-ols. Studies have shown that the accumulation pattern of flavan-3-ols in grape berries exhibited a trend of increasing and then decreasing ( Padilla-González et al, 2022 ), generally reaching the highest concentration at the véraison stage, and then showing a decreasing trend, but the synthesis of anthocyanin showed a rapid accumulation process during the véraison stage. In combination with the phenological period, vintages with insufficient light often have more rainfall during the véraison stage, and rainfall slows down the accumulation of anthocyanin and flavonol, while the decomposition rate of flavan-3-ol decreases, which in turn causes the phenomenon of low anthocyanins and flavonols concentrations and high flavan-3-ols concentrations in berries at maturity in vintages with insufficient light and more rainfall ( Blancquaert et al, 2019 ).…”

Optimization of Extraction and HPLC–MS/MS Profiling of Phenolic Compounds from Red Grape Seed Extracts Using Conventional and Deep Eutectic Solvents

“…Results obtained for total flavan-3-ol content, as the phenol group most-specific to grape seeds, also differed from variety to variety. As reported before, flavan-3-ol diversity in grape seeds is primarily influenced by species, variety and environment [ 51 ]. Finally, even though higher values were observed for EtOH extracts, statistical significance was not reached ( p = 0.1892).…”