Metabolic profile and bioactivity of the peel of Zhoupigan (Citrus reticulata cv. Manau Gan), a special citrus variety in China, based on GC-MS, UPLC-ESI-MS/MS analysis, and in vitro assay

Zhoupigan (Citrus reticulata cv. Manau Gan) is a local citrus variety in China. Its peel, known as Zangju peel (ZJP). The metabolic profile and bioactivity of ZJP have not been adequately studied, resulting in underutilization of ZJP and a serious waste of resources. In this study, GC-MS identified 46 components in ZJP, which defined ZJP's distinct aroma. Furthermore, UPLC-ESI-MS/MS detected 1506 metabolites in ZJP, and the differential metabolites were primarily involved in the biosynthesis of flavonoids and phenylacetone. Additionally, 56 key differential metabolites with metabolic pathways were identified. ZJP had significant antioxidant activity and the enzyme inhibitory activity ranking as pancreatic lipase (IC50 = 3.71 mg/mL) > alpha-glucosidase (IC50 = 6.28 mg/mL) > alpha-amylase (IC50 = 8.02 mg/mL). This study aimed to evaluate the potential of ZJP as natural antioxidant and functional food source and to serve as foundation for the further development of ZJP products with specific functional attributes.