Power ultrasound for valorization of Citrus limon (cv. Eureka) waste: Effects of maturity stage and drying method on bioactive compounds, antioxidant, and anti-diabetic activity

Abstract

This study aims to use power ultrasound-assisted extraction (UAE) and maceration (ME) to valorize lemon juice processing residues (flavedo+albedo). Also, the effects of maturity stage (mature vs. immature) and drying method (freeze-drying-FD vs. oven drying-OD) on antioxidant activity, digestive enzymes inhibition, and bioactive compounds (phenolics and flavonoids) were analyzed. Besides. effects of independent parameters were elaborated through principal component analysis (PCA). According to the results, immature lemons exhibited a higher inhibition of α-amylase, α-glucosidase, and lipase by 10, 5, and 46%. Also, replacing OD with FD enhanced the antioxidant activity. HPLC identified hesperidin and sinapic acid as the most abundant bioactive compounds in all extracts and UAE enhanced their concentration by 2.3 and 1.2 times, respectively. Besides, sonication enhanced antioxidant activity and anti-diabetic effects by 1.1–5.6 times. Therefore, replacing mature peels, OD, and ME with immature peels, FD, and UAE can boost the potential health benefits of extracts of lemon processing by-product.