Screening grape seeds recovered from winemaking by-products as sources of reducing agents and mammalian α-glucosidase and α-amylase inhibitors

Grape seeds collected from vinification of various grape varieties were extracted by supercritical CO2 for oil recovery. The defatted residues thus obtained were considered as a re-utilisable co-product and assessed for phenolic content, reducing capacity and inhibitory activities against mammalian -amylase and -glucosidase enzymes. Supercritical CO2 treatment led to higher recovery of anthocyanins. Reducing capacity of phenolic extracts reached up to similar to 2200 mmolFe(II)kg(-1), much higher than that of various natural phenolic sources. The anthocyanin-rich extracts showed the highest inhibitory effectiveness towards -glucosidase (I-50 value equal to similar to 40g gallic acid equivalents (GAE)/mL similar to half than acarbose). Inhibitory effectiveness towards -amylase activity was similar among grape varieties, with I-50 values comparable to that of acarbose and correlated with proanthocyanidin contents. These results could pave the way for an efficient processing of grapes, including cascade processes, namely: winemaking, oil extraction from recovered grape seeds and phenolic extraction from defatted grape seeds as potential cost-effective nutraceuticals.