Optimization of Ultrasonic-Assisted Extraction of Phenolic Compounds from Eggplant Peel and Its Hypoglycemic Effect

Objective: In order to improve the added value of eggplant peel, the best method of phenolic compounds from eggplant peel (EPP), as well as its hypoglycemic impact in vitro and in vivo were studied. Methods: EPP was extracted by ultrasonic-assisted method. The extraction parameters of EPP were optimized by single factor experiments and orthogonal experiment with yield as evaluation index. The inhibitory rate of EPP on α-glucosidase and its effects on body weight, fasting glucose, and glucose tolerance in mice were analyzed to evaluate its hypoglycemic efficacy in vitro and in vivo. Results: The optimal extraction conditions were as follows: Ultrasonic power 540 W, solid-liquid ratio 1:50 g/mL, extraction temperature 50 ℃ and extraction time 50 min. The extraction yield of EPP was 43.21%. The inhibitory rate on α-glucosidase increased with the increase of EPP concentration, and the inhibition rate of α-glucosidase was 45.46% with 1 mg/mL EPP. The body weight, fasting blood glucose and glucose tolerance of diabetic mice could be improved by EPP, and it had a significant hypoglycemic effect on diabetic mice. Conclusion: This study confirmed that EPP had hypoglycemic effect, which laid a theoretical foundation for comprehensive development and utilization of eggplant peel.