Abstract
Grape pomace seeds and skins from different Mediterranean varieties (Grenache [GRE], Syrah [SYR], Carignan [CAR], Mourvèdre [MOU] and Alicante [ALI]) were extracted using water and water/ethanol 70% in order to develop edible extracts (an aqueous extract [EAQ] and a 70% hydro-alcoholic extract [EA70]) for potential use in nutraceutical or cosmetic formulations. In this study, global content (total polyphenols, total anthocyanins and total tannins), flavan-3-ols and anthocyanins were assessed using HPLC-UV-Fluo-MSn. In addition, extract potential was evaluated by four different assays: Oxygen Radical Absorbance Capacity (ORAC), Ferric Reducing Antioxidant Potential assay (FRAP), Trolox equivalent antioxidant capacity (TEAC) or ABTS assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. As expected, seed pomace extracts contained higher amounts of polyphenols then skin pomace extracts. Indeed, seeds from Syrah contained a particularly important amount of total polyphenols and tannins in both type of extract (up to 215.84 ± 1.47 mg of gallic acid equivalent [GAE]/g dry weight (DW) and 455.42 ± 1.84 mg/g DW, respectively). These extracts also expressed the highest antioxidant potential with every test. For skins, the maximum total phenolic was found in Alicante EAQ (196.71 ± 0.37 mg GAE/g DW) and in Syrah EA70 (224.92 ± 0.18 mg GAE/g DW). Results obtained in this article constitute a useful tool for the pre-selection of grape pomace seed and skin extracts for nutraceutical purposes.
Highlights
Phenolic compounds are currently receiving much attention because of their beneficial health effects related to their ability to protect against oxidative cell damage when antioxidant and pro-oxidant imbalances occur
This study demonstrated that correlations between grape pomace contents and antioxidant levels were higher with total values than with the specific compound concentrations quantified by HPLC
This study showed that grape pomace seed and skin extracts still contained appreciable amounts of flavan-3-ols and anthocyanins, despite extraction during vinification
Summary
Phenolic compounds are currently receiving much attention because of their beneficial health effects related to their ability to protect against oxidative cell damage when antioxidant and pro-oxidant imbalances occur. Antioxidant defense strategies are committed to prevent the oxidative attack in its early moments by the formation of priming radicals as well as during the initiation and chain propagation stages under stress condition or during aging processes, excessive levels of reactive species may interrupt regular processes. Polyphenolic compounds serve as reducing agents in many biological systems by donating hydrogen, quenching singlet oxygen, acting as chelators and by trapping free radicals. These antioxidant activities can help to limit oxidation of nucleic acids, proteins, lipids, which may initiate degenerative diseases such as neuro-degenerative disease, cancer, heart disease, chronic inflammation, dermal disorders and aging [6,7,8]
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