Potential of different fractions of polyphenols in persimmon peels: Phenolic profiles, bio-activities, and mechanism of inhibition against α-glucosidase.

To improve the value of persimmon peels (a waste of persimmon product), this study explored the potential of persimmon peels polyphenols using conventional extraction (CE), ultrasound-assisted extraction (UAE), and subcritical solvent-assisted extraction (SAE), combined with electron beam irradiation (EBI) pretreatment (E-CE, E-UAE, E-SAE). Furthermore, the total phenolic content, total flavonoid content, condensed tannins, antioxidant activity, and α-glucosidase (α-GLU) inhibition of five polyphenol fractions (free, soluble esterified/glycoside, insoluble esterified/glycoside types) were analyzed. SAE and E-SAE significantly improved extraction efficiency, particularly for free phenolics (FP), which exhibited superior bio-activities. Structural analyses revealed SAE disrupted persimmon peel's microstructure and crystalline form. UHPLC-MS showed SAE and E-SAE had lower polyphenol diversity but higher bioactivity than CE. Kinetic analysis indicated these polyphenols reversibly inhibited α-GLU via a mixed competitive mechanism, forming non-fluorescent complexes and inducing enzyme conformational changes. These findings support persimmon peel upcycling and their polyphenols as natural α-GLU inhibitors for postprandial blood-glucose control.