The (Poly)phenolic Profile of Separate Winery By-Products Reveals Potential Antioxidant Synergies

Abstract

The by-products of grapes (Vitis vinifera L.) in the winemaking process present a diverse phytochemical profile of (poly)phenols, essentially represented by phenolic acids, flavonoids, and stilbenes, which have health benefits. In winemaking, solid (grape stems and pomace) and semisolid (wine lees) by-products are generated, negatively impacting the sustainability of the agro-food activity and the local environment. Although information on the phytochemical profile of grape stems and pomace has been reported, especially information concerning (poly)phenols, research on wine lees is necessary to take advantage of the compositional traits of this residue. So, in the present work, an updated, in-depth comparison of the (poly)phenolic profiles of these three resulting matrices in the agro-food industry has been carried out to provide new knowledge and interesting data on the action of yeast and lactic acid bacteria (LAB) metabolism in the diversification of phenolic composition; additionally, we extract complementarities for the possible joint application of the three residues. The phytochemical analysis of the extracts was carried out using HPLC-PDA-ESI-MSn. The (poly)phenolic profiles of the residues showed significant discrepancies. The results obtained showed that the greatest diversity of (poly)phenols was found in the stems of the grapes, followed closely by the lees. Through technological insights, it has been suggested that yeasts and LAB, responsible for the fermentation of must, might play a key role in the transformation of phenolic compounds. This would provide new molecules with specific bioavailability and bioactivity features, which might interact with different molecular targets and, consequently, improve the biological potential of these underexploited residues.

New anti-α-Glucosidase and Antioxidant Ingredients from Winery Byproducts: Contribution of Alkyl Gallates

“…Although the occurrence of gallic acid, methyl, and ethyl gallates have been previously reported in winery byproducts such as grape (V. vinifera L.) stems, seeds, and pomace, , the present study enabled for the first time, as far as we know, the detection and identification of propyl gallate, butyl gallate, octyl gallate, and lauryl gallate in grape stems and pomace, and wine lees. From these newly reported alkyl gallates, to the best of our knowledge, only butyl gallate has been previously described as a natural product found in Alchornea glandulosa .…”

“…In this context and according to the gallic acid and galloyl esters burden of the diverse matrices assessed, alkyl gallates may provide a valuable contribution to the overall radical scavenging activity and the different evolution of the radical scavenging capacity of the three separate matrix after the dehydration process. In this regard, the phenolic profile of wine lees, formed to some extent with the concourse of the yeasts metabolism could be more resistant to the thermal treatment applied with stabilization purposes, as recently demonstrated by Costa-Pérez et al (2023) . Specifically, (poly)­phenolic compounds featured by low polarity (e.g., unesterified quercetin or kaempferol), could effectively contribute to the higher radical scavenging power of this matrix.…”

“…Nonetheless, the extracts could also contain certain amounts of (poly)­phenols, especially regarding those features by a low polarity (e.g., nonesterified flavonols). In this concern, according to previous comprehensive characterizations of the (poly)­phenolic profile of the matrices under study developed by our own group, these compounds were only in significant concentration in wine lees where these could coadyuvate the antioxidant activity developed by alkyl gallates. Anyway, this fact should be overcome by analyzing in the frame of future investigations the actual concentration of (poly)­phenols and alkyl gallates in final extracts addressed to be included as an ingredient in the development of new added-value commodities or even in the bioaccessible fraction of functional ingredients.…”

“…In this regard, the phenolic profile of wine lees, formed to some extent with the concourse of the yeasts metabolism could be more resistant to the thermal treatment applied with stabilization purposes, as recently demonstrated by Costa-Peŕez et al (2023). 23 Specifically, (poly)phenolic compounds featured by low polarity (e.g., unesterified quercetin or kaempferol), could effectively contribute to the higher radical scavenging power of this matrix. Beyond this, the interaction of the antioxidant compounds present in the three matrices under consideration with additional components of wine lees (present in lower concentration in grape stems and pomace) during the manufacturing process could give rise to the formation of new highly antioxidant compounds (such as alkyl gallates) that would entail enhanced antioxidant potential in comparison with grape stems and pomace.…”

Winery By-Products as Sources of Bioactive Tryptophan, Serotonin, and Melatonin: Contributions to the Antioxidant Power

“…However, the presence of other hydrophilic compounds in the samples seems to influence the antioxidant capacity, as wine lees showed higher results compared to grape pomace, although its tryptophan content was significantly lower ( Table 2 ). Recent results from our group described a higher total content of (poly)phenolic compounds in grape stems compared to grape pomace and wine lees [ 46 ]. Thus, although the extraction method for tryptophan is not the optimal choice for the extraction of phenolic compounds, a part of them could be released during the specific process applied for the analytes focused on the objectives of the present work, contributing to the overall antioxidant capacity recorded ( Table 2 ).…”