Physico-Chemical Characterization, Phenolic Compound Extraction and Biological Activity of Grapevine (Vitis vinifera L.) Canes

Abstract

Annual grapevine pruning produces large amounts of unused waste as woody canes. The current study is aimed at the sustainable valorization of viticultural waste by establishing phenolic compound extraction conditions, composition, and biological potential of crude and purified cane extracts of three Vitis vinifera L. cultivars growing in temperate climate conditions. Grapevine canes proved to be rich in carbohydrates and minerals; chlorophyll and carotenoids were also quantified. The highest yield of phenolic compounds was obtained when dry canes (<0.5 mm) were subjected to liquid–solid extraction (1:20 w/v) with 70% (v/v) ethanol, for 4 h at 35 °C, after a preliminary ultrasound treatment (6 min., 42 KHz); Pinot Gris canes showing the highest concentration of flavonoids and non-flavonoids. Stilbenes (resveratrol) and flavan-3-ols (catechin and epicatechin) were the main phenolic representative, resveratrol concentrations varying significantly between red-black (419.01–425.60 μg/g d.w.) and white (282.19 ± 4.14 μg/g d.w.) grape cultivars. Purified extracts (C-18 cartridge) exhibited higher antioxidant and antiradical activities compared to the crude extracts, and a higher antimicrobial effect, especially against Gram-positive (Staphylococcus aureus) pathogenic bacteria. Furthermore, Saccharomyces cerevisiae and Oenococcus oeni showed a reduced susceptibility even at high extract concentrations (>100 mg/mL). These findings indicate that grapevine canes represent a valuable source of natural bioactive compounds, that are currently insufficiently known and not exploited to their true functional and economic potential.