Ultrasound-optimized phenolic recovery from feijoa (Acca sellowiana) peel: Cultivar variability, antioxidant capacity, and in vitro starch digestion.

Acca sellowiana (feijoa) peel is a rich phenolic source. Response surface methodology with the central composite design was employed to optimize ultrasound-assisted extraction (UAE) parameters (46 °C, 50 % ethanol, 35 min) for feijoa peel phenolics, yielding 116.30 mg GAE/g DW TPC. Comparative analysis across cultivars identified Gemini with the highest TPC (133.0 mg GAE/g DW) and DPPH activity (671.07 μmol TE/g DW), while Mammoth showed the highest ABTS (2087.78 μmol TE/g DW) and FRAP (896.16 μmol TE/g DW) values. In vitro digestion revealed potent starch-digestion inhibition by early-maturing cultivars: Gemini suppressed α-amylase (IC50 = 0.06 mg/mL), and Unique targeted α-glucosidase (IC50 = 0.74 μg/mL). Molecular docking highlighted hydrogen bonding and hydrophobic interactions between key phenolics (procyanidin B1, ellagic acid) and catalytic residues (ASP-197, ASP-300, ASP-69, ASP-215) of starch-digesting enzymes. These findings support feijoa peel's valorization as a functional ingredient for anti-glycation beverages, nutraceutical capsules targeting diabetes management, and pharmaceutical adjuvants.