Characterization and biological effects of extracts from winery by-products

Abstract

Pomace, stem, grapevine leaves, and vine shoots arise as so called winery by-products during the wine production process. Due to their high content of secondary plant metabolites, such as polyphenols, their usage as sources of bioactive compounds offers an opportunity to obtain value-added products for the food and pharmaceutical industry. The aim of the present study was to investigate extracts from winery by-products of Vitis vinifera L. cv. Riesling from the region ‚Pfalz‘ in Rhineland-Platinate, Germany with regard to their chemical composition and biological effect in vitro. Total phenolic contents (TPC) of pomace, stem, vine leaf, and vine shoot extracts were determined by Folin-Ciocalteu method and polyphenolic profiles were characterized by HPLC-UV/Vis-ESI-MS/MS. The extracts showed TPCs ranging from 432 to 665 mg GAE/g extract. Besides flavanols, as for example catechin, epicatechin and procyanidins, phenolic acids and flavonols, such as quercetin und kaempferol derivates were tentatively identified, amongst others, by HPLC-UV/Vis-ESI-MS/MS analysis in the negative ion mode. Stilbenes represent an additional group of polyphenols present in the extracts from winery by-products, including trans-resveratrol, piceid, piceatannol and ε-viniferin being identified. In the human hepatocarcinoma cell line HepG2 effects of the extracts on cell viability, intracellular ATP, the mitochondrial membrane potential (MMP), and tert-butyl hydroperoxide (TBH)-induced intracellular reactive oxygen species (ROS) were determined in vitro. Dose-dependent cytotoxic effects were observed besides protective effects regarding TBH-induced intracellular ROS level, and partially impaired MMP. Thus, winery by-products represent interesting sources of bioactive compounds exerting positive and/or negative effects on mitochondrial function in liver cells.