Grape leaves and canes as sources of high-value bioactive compounds: chemical characterization, antioxidant, and tyrosinase-inhibitory properties

Abstract

Grapes are one of the worldʼs most important crops. Tons of liquid and solid waste are produced from winemaking and viticultural activities. Management of by-products is essential not only for achieving sustainability, but also for developing new ingredients for the food, pharmaceutical, and cosmetic industries. In the current study, we investigated the potential of grape cane (GCE) and leaf (GLE) ethanolic extracts as multifunctional cosmetic ingredients, obtained from 5 different varieties, both Greek and international, namely “Assyrtiko”, “Rhoditis”, “Muscat dʼHamburg”, “Syrah” and “Merlot”, cultivated in Thessaly, central Greece. Their chemical characterization was performed with LC-MS, whereas the quantification of the major ingredients with HPLC-DAD. A total of 18 and 15 compounds were identified and 8 and 5 of them were quantified in GCE and GLE, respectively. Stilbenoids were the most abundant phenolics in GCE, with trans-resveratrol and (E)-viniferin dominating, whereas hydroxycinnamic acids represented by caftaric acid, and flavonols, especially quercetin glycosides, were the most abundant in GLE. Antioxidant activity was assessed with the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging and the Ferric Reducing Antioxidant Power assays. All extracts showed rich antioxidant potential, yet the highest was exerted by Syrah GLE. The skin whitening capability of GCE and GLE was investigated using a mushroom tyrosinase inhibition assay and the results showed strong inhibitory activity. Overall, our findings demonstrate that grape canes and leaves could be valorized by generating bioactive extracts used as antioxidants and skin whitening raw materials in the cosmetic industry, satisfying the increasing interest for natural active ingredients among consumers.