Sorbus spp. berries extraction in subcritical water: Bioactives recovery and antioxidant activity

With the aim of developing a sustainable and efficient extraction of polyphenols-rich fraction from Sorbus spp., Microwave-Assisted Subcritical Water Extraction (MASWE) was selected as the technique of choice. Although Sorbus spp. berries are rich in nutraceutical compounds, they are generally underutilised. The extracts obtained contain caffeoylquinic acids (i.e. chlorogenic acids), flavonoids, and organic acids, all of which are active components with potential applications in innovative functional foods due to their potent antioxidant activity. To optimise the extraction protocol, different temperatures and different species of the above genus were studied to improve the recovery of the polyphenolic fractions and obtain products with potential high bioactivity. The best resulting sample was studied more in detail using different colorimetric assays (total content of polyphenols, flavonoids and sugars - TPC, 406.43 mgGAE/gext; TFC, 13.5 mgQE/gext; TSC, 454.1 mgGlu/gext), purification streams, and LC-MS analyses. However, the most remarkable property observed is the outstanding antioxidant activity of the extract (4.74 mmolTrolox.eq/gext). In order to obtain a refined product rich in bioactive compounds, a purification protocol was performed leading to a final TPC selectivity of about 87 % and 10.12 mmolTrolox.eq/gext. Qualitative LC-MS analyses helped to identify chlorogenic acids as predominant in the extract, along with methyl esters of sorbic acid.