Analysis Of The Chemical Composition Of The Peel Of Different Cultivars Of Citrus Grandis [L.] Osbeck

Objective:（1）To analyse and identify the chemical composition contained in the peel of several varieties of pomelo;（2）To determine the content of several important compounds in the peel of pomelo;（3）To compare the differences in the compounds contained between the peels of different varieties of pomelo.Method:（1）Ultraperformance liquid chromatography-Q-exactive orbitrap tandem MS（UPLC-Qexactive orbitrap-MS）method was applied for the compositional analysis of extracts from five varieties of pomelo peel samples using supercritical CO₂fluid extraction technique and methanolic extracts of pomelo peel.（2）The compositional analysis of the essential oil of pomelo peel was carried out by gas-mass spectrometry（GC-MS）.（3）High performance liquid chromatography was used to determine the specific contents of naringin,rhoifolin,meranzin hydrate,isomeranzin,auraptene,and bergamottin in the peel of pomelo.Results:（1）In this study,we developed a reliable and comprehensive method based on supercritical fluid extraction combined with UPLC-Q-Exactive Orbitrap-MS to detect eight flavonoids,18 coumarins,four organic acids,three aldehydes and 12other compounds in pomelo peel extracts.Of the compounds identified,25 were found for the first time in pomelo peel and,in addition,there were differences in compound species between the five species,which may contribute to the different functional and medicinal values.（2）In this study,the volatile components in pomelo peel were qualitatively and quantitatively analysed using gas chromatography-mass spectrometry（GC-MS）.In addition,a total of 194 volatile compounds were detected in the selected pomelo peel samples in this study.The results indicated that pomelo peel volatile oil was rich in D-limonene,a compound with a variety of biological activities.Twenty major volatile compounds in pomelo peel were analysed in this study.The types of major volatile components in pomelo peel were similar,but the content of major volatile components in the peel of different pomelo varieties varied.In general,Citrus grandis cv.Shatianyou and Citrus grandis cv.Liangpingyou had similar composition of volatile components,while Guanximiyou,Citrus grandis cv.Yuhuanyou,Citrus grandis cv.Duweiwendanyou had a more similar composition of volatile components,all with high levels of D-limonene.（3）In this study,the non-volatile components were identified using UPLC-Q-Exactive Orbitrap-MS,and then the content of the six main active components in pomelo peel was determined using HPLC-PDA.In this study,a total of 53 major chemical components were identified in the methanolic extract of pomelo peel.At the same time,we observed that the composition of the six active ingredients in the peel of individual pomelo can be roughly divided into two groups,one group being Citrus grandis cv.Shatianyou and Citrus grandis cv.Liangpingyou,and the other group including Citrus grandis cv.Guanximiyou,Citrus grandis cv.Yuhuanyou,Citrus grandis cv.Duweiwendanyou.Conclusion:（1）A total of 45 compounds were identified in supercritical carbon dioxide fluid extracts from five different varieties of pomelo peel,25 of which were first found in grapefruit peel.Pomelo peel is rich in flavonoids and coumarins.In addition,there are differences in the types of compounds among the five varieties,which may contribute to the formation of different functions and medicinal values.（2）A total of 194 volatile compounds were detected in the volatile essential oil of pomelo peel.The varieties show obvious clustering and differences.（3）The contents of naringin,rhoifolin,meranzin hydrate,isomeranzin,auraptene,and bergamottin in the peels of different varieties of pomelo varied among the 12 batches of pomelo.This indicates that the six important compounds mentioned above differed between cultivars and origins.