Thermal valorization of purple sweet potato peel waste into peonidin-rich extracts with antiallergic potential

Purple sweet potato peel is an agricultural waste by-product that contains high concentrations of anthocyanins. Seven peonidin-based anthocyanins with mono- and di-acylation were identified in fresh peel and thermal processes (drying and steaming). Major anthocyanins included Peo-3-(phb-soph)-5-glc, Peo-3-(feruloyl-soph)-5-glc, and Peo-3-(caffeoyl-phb-soph)-5-glc. Increasing extraction time to 30 min enhanced the extraction of anthocyanins in all samples, but glucose and fructose contents decreased after 20 min of incubation. High suppression of β-hexosaminidase release in RBL-2H3 cells was found in the steaming and drying processes, with IC 50 values of 2.85 mg/mL and 3.24 mg/mL, respectively. Differences in the content and types of peonidin-based anthocyanins led to increased antiallergic activity. Anthocyanins from purple sweet potato peel extract inhibited mast cell degranulation, as shown by synchrotron-based infrared microspectroscopy. The protein pattern (Amide I ) in the blank and treated cells with peel extract exhibited the α-helix structure (1649 and 1652 cm −1 ), while the control manifested the β-sheet structure (1637 cm −1 ). Results indicated the ability of anthocyanin to prevent IgE-mediated allergic reactions. The valorization of purple sweet potato peel through thermal processing, extraction, and monitoring cell activity creates a sustainable circular economy model by minimizing agricultural waste and developing high-value functional ingredients.