Grape juice by-products extracted by ultrasound and microwave-assisted with different solvents: a rich chemical composition

By-products of the grape juice industry contain valuable compounds. The current work produced bioactive-enriched extracts from by-products of the grape juice, through three different extraction methods. Yields and chemical compositions varied, according to the extraction method (ultrasound, microwave, liquid–liquid). High-efficiency liquid chromatography with UV–Vis and high-resolution mass spectrometry characterised were used for chemical characterization, with glycosylated flavonoids evident. The crude extract was fractionated by open column, which has possibility carried-out fraction rich in resveratrol. The inhibition of DPPH radicals ranged from 14.2 to 74.2%, and the total phenolic content ranged from 0.1 to 107.0 mg gallic acid equivalents/100 g. Microwave-assisted extraction of grape juice by-products using polar solvents, such as ethanol and water, provided the best yield and chemical composition, obtaining extracts rich in flavonoids. In this way, this work has demonstrated the industrial grape by-products importances, which are a rich source of antioxidants if properly extracted.