Identifying Major Drivers of Antioxidant Activities in Complex Polyphenol Mixtures from Grape Canes

Abstract

Grape canes represent a valuable source of numerous polyphenols with antioxidant properties, whose compositions vary depending on the genotype and environmental factors. Antioxidant activities of pure molecules are often reported without considering possible interactions that may occur in complex polyphenol mixture. Using UPLC-MS-based metabolomics and unsupervised classification, we explored the polyphenol variations in grape cane extracts from a collection of European varieties. Antioxidant activities were assessed using ORAC, ABTS, DPPH, FRAP, CUPRAC and chelation assays. Pairwise correlations between polyphenols and antioxidant capacities were performed to identify molecules that contributed more to the antioxidant capacities within a complex mixture of polyphenols.

Background and Perspectives on the Utilization of Canes’ and Bunch Stems’ Residues from Wine Industry as Sources of Bioactive Phenolic Compounds

“…Due to its high selectivity, HPLC-MS/MS allows the sensitive and simultaneous detection and identification of a large number of compounds (even coeluting), but with different mass spectra in a single run and is therefore the method of choice. Many papers employed triple quadrupole mass detection, ,,,,,, although for identification purposes high-resolution mass detectors, both Q-TOF ,, and Orbitrap , have been particularly useful. NMR, on the other hand, is a high-performance nondestructive method that allows the identification and quantification of metabolites.…”

“…Antioxidant activity is a common characteristic shared by the different classes of PCs related to the chemical properties that derives from their chemical structure, the presence of conjugated double bonds and/or functional groups bonded to the phenolic ring. The antioxidant properties of tissues of many plant species are mainly correlated with the content of these metabolites . The term antioxidant describes a set of chemical mechanisms that are responsible for the protection of cells against the action of free radicals .…”

“…Several in vitro studies have shown the remarkable antioxidant activity of bunch stem and cane extracts. ,,,,,,,,,,,,− Instead, this property is less well documented in in vivo trials, given the limited knowledge about its absorption in humans. The comparison of the antioxidant values reported in the literature is a complex task given the lack of standardized methods as well as in the expression of results.…”

“…The comparison of the antioxidant values reported in the literature is a complex task given the lack of standardized methods as well as in the expression of results. The TAC concept comprehend individual antioxidant actions of different compounds and their additive, synergistic, antagonistic interactions or “entourage” effect in raw extracts, food samples and biological fluids. , The most commonly used in vitro assays to measure TAC include 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC), ferric ion reducing antioxidant power (FRAP) and the Cu 2+ reducing power (CUPRAC). These tests are classified according to the reaction mechanism into two groups: ABTS, DPPH, FRAP and CUPRAC are based on electron transfer (ET) and involve the reduction of a colored oxidant, while ORAC is based on atom transfer of hydrogen (HAT), in which antioxidant and substrate compete for thermally generated peroxyl radicals. , It is necessary to consider that these assays measure the TAC of a sample under defined conditions prescribed by the method and strictly based on the in vitro chemical reaction, so the bioactivity of a sample cannot be only explained by these assays or their interactions .…”

“…The antioxidant properties of tissues of many plant species are mainly correlated with the content of these metabolites. 133 The term antioxidant describes a set of chemical mechanisms that are responsible for the protection of cells against the action of free radicals. 70 Free radicals, known as reactive oxygen species (ROS) and/or reactive nitrogen species (RNS), are naturally generated in cells through various endogenous reactions.…”