Comparative Study On Chemical Constituents Of Chenpi And Citrus Peels From Different Sources

Citri Reticulatae Pericarpium(Chenpi),the dry mature peel of Citrus reticulate Blanco or its cultivated varieties,has been extensively used as well-known traditional Chinese medicine in China.The chemical composition and biological activities of Chenpi differ significantly due to its different cultivars and growing environments.As the typical source of Chenpi,citrus(Citrus spp.)have been cultivated in the south of China.Many studies on the quality of citrus peels have been reported,but the quality of citrus peels has not been systematically evaluated from the perspectives of micromolecules and macromolecules.At first,a reliable HPLC-PDA analytical method was established for the determination of five compounds in fourteen batches of Chenpi.According to five compounds contents,the content of narirutin in Chenpi from Guangdong and Sichuan provinces is lower,while the contents of nobiletin and tangeritin are higher.The Chenpi from Fujian,Anhui,Zhejiang,Shandong and Hunan provinces have a higher content of narirutin,while the contents of nobiletin and tangeritin are lower.The antioxidant and α-glucosidase inhibitory activities of all Chenpi were studied.The correlation analysis results showed that nobiletin and tangeretin are the main contributors to the antioxidant capacity of Chenpi,and narirutin is the main active component to inhibit the activity of α-glucosidase.Meanwhile,an UHPLC-Q-Orbitrap method was established and successfully applied for the determination of different cultivars citrus peel samples.The untargeted metabolomics analysis reveals distinct differences between Lukan peel and Gongchuan peel.A total of 59 metabolites,which cover 49 flavonoids,4 limonoids,3alkaloids,and 3 organic acids,were unambiguously identified in samples.Furthermore,the results of multivariate statistical analysis showed that Lukan peel and Gongchuan peel had remarkable discrimination,and 10 compounds were selected as potential chemical markers for samples classification,including 9 flavonoids and 1limonoids.Finally,Pectins obtained from citrus peel of different cultivars and growth regions were compared based on physicochemical properties and antioxidant activity in vitro.Results showed that the different cultivars and growing areas have significant effects on the properties of citrus peel pectins.Citrus peel pectins extracted by acetic acid were highly heterogeneous polysaccharides with broad molecular weight distributions and had high proportions of the rhamnogalacturonan I domain.Among the 10 citrus peel pectins,Shatangju peel pectin and Xuecheng peel pectin own superior antioxidant biological activity,Dahongpao peel pectin and Buzhihuo peel pectin had excellent functional properties.According to the correlation analysis,molecular weight,galacturonic acid content and degree of esterification were beneficial to increase the thermal stability and viscosity of citrus peel pectins,while the rhamnose content,rhamnogalacturonan I region and lower molecular weight can improve citrus peel pectins antioxidant activity.