Carbohydrase-assisted extraction of phenolic compounds from citrus peel: chemical composition and cellular...

Citrus peels are rich in phenolic compounds. Carbohydrases have demonstrated efficacy in extracting phenolic compounds from fruit byproducts. However, the recovery rate of phenolics from citrus peels using carbohydrase-assisted extraction is significantly lower. The potential for enhanced recovery of phenolic compounds from citrus peels by combining carbohydrase pretreatment with solvent extraction requires further investigation.

The morphology of peel residues indicated a degradation effect on the cell wall structure. Pretreatment with pectinase or viscozyme L significantly increased the total phenolic contents (21.88 and 25.55 g GAE kg^-1 DW) and total flavonoid contents (40.33 and 37.13 g RE kg^-1 DW). Both pretreatments also significantly enhanced the intracellular antioxidant activities of the peel extracts, with cellular antioxidant activity values of 3.37 and 4.58 μmol quercetin equiv. g^-1 DW, respectively. A total of 76 compounds were identified, including 42 polymethoxylated flavonoids, 19 flavonoid glycosides, 6 flavonoid aglycones, 8 coumarins and a limonoid. Notably, hesperidin was the most dominant compound, reaching its highest concentration (9.53 g kg^-1 DW) in the pectinase pretreatment group. The deglycosylation of flavonoid glycosides was induced by pectinase and viscozyme L pretreatment, and the degradation products contributed to the enhanced cellular antioxidant activity of the resulting extracts.

The combination of carbohydrase (like pectinase and viscozyme L) pretreatment and ethanol extraction can significantly enhance the recovery of phenolic compounds from citrus peels, thereby improving their cellular antioxidant activities. These methodologies have the potential to transform citrus peels into high-value products. © 2025 Society of Chemical Industry.