PEG 200-Assisted Ultrasound Extraction and Characterization of Mulberry Anthocyanins: Optimization, Bioactivities, and Stability

Mulberry anthocyanins are promising natural pigments and bioactive compounds, but their efficient recovery is limited by processing-induced degradation. In this study, polyethylene glycol (PEG)-assisted ultrasound extraction was investigated for recovering anthocyanins from Morus nigra fruits. Four PEG grades (PEG 200, 300, 400, and 600) were initially screened, after which PEG 200 was selected for process optimization using response surface methodology with a central composite design. The effects of PEG concentration, extraction time, ultrasonic power, and temperature on total monomeric anthocyanin content were evaluated. The optimized conditions were 75% PEG 200, 18 min, 420 W, and 40 °C, yielding 515.78 ± 0.53 mg cyanidin-3-O-glucoside equivalents/100 g dry weight. C18 solid-phase extraction was subsequently used to obtain an anthocyanin-enriched fraction for spectroscopic and mass-spectrometric characterization. FT-IR analysis indicated functional groups consistent with phenolic and glycosidic constituents, while UHPLC-Q-TOF-MS/MS enabled the tentative annotation of five anthocyanin-related compounds. The optimized crude extract exhibited antioxidant, α-amylase and α-glucosidase inhibitory and antibacterial activities under the respective in-vitro assay conditions. Anthocyanin retention was higher under dark and low-temperature conditions than under fluorescent illumination and elevated temperatures. Overall, the results demonstrate the feasibility of PEG 200-assisted ultrasound extraction for recovering anthocyanin-rich mulberry extracts and provide complementary information on their chemical characteristics, in-vitro bioactivities, and stability.