Study On The Composition And Activity Of Main Pomelo Peels In China

Citrus maxima(Burn.)Merr.is one of the basic species of the genus Citrus in Rutaceae.Pomelo,the fruit of Citrus maxima(Burn.)Merr.,has a long history of cultivation in China,its wide variety of planting area and yields have reached the top in the world.The fruit volume of pomelo is larger than other citrus fruit,the quality of pomelo peels accounts for 30%-40%of the whole fruit.Pomelo peels usually contains many biologically active compounds such as essential oils,flavonoids,pectin and polysaccharides.Traditional Chinese medicine believed that pomelo peels could use for relieving coughs and eliminating phlegm,moderm medical research showed that the extract of pomelo peels has antioxidant,anti-aging,anti-cancer,anti-microbial,hypoglycemic action and other activities.Since the pomelo is mainly eaten in fresh currently,the peels are mostly discarded.The annual output of pomelo in China is about 4million tons,which means more than 1.2 million tons of peels will be discarded each year.Pomelo peels which mostly discarded as waste not only causes environmental burden,but also causes serious waste of resources due to insufficient development of the secondary metabolites in peels.In this work,the essential oils(EOs)were isolated and identified,and its four biological activities were tested.The content and two biological activities of flavonoids were studied.In addition,the performance on the oil absorption capacity of cellulose in pomelo peels was discussed.The specific research contents as follows:1.EOs from 12 pomelo peels were obtained by steam distillation,the yield distribution of EOs was 0.34%to 1.53%.The chemical components in the EOs were analyzed by GC-MS,50 compounds were identified and consisted mainly of monoterpenes and sesquiterpenes with identification rate from 90.38%to 98.97%.The relative content of compounds was determined by area normalization method,d-limonene(4I1.43%-89.91%),?-myrcene(2.42%-30.37%)and nootkatone(0.47%-7.90%)were identified as the main composition in EOs.On the basis of compositions of the EOs,the principle component analysis(PCA)and the hierarchical clustering analysis were performed to explain the phytochemical variations for the 50 identified compounds and divided 12 pomelo peels into 3 cluster.Liangping Yu,Shatian Yu(Guangxi)and Jinlan Yu were divided into Clusterl,Yuhuan Wendan,Chumen Wendan and Guanxi Pinghe honey pomelo were divided into Clusterll.Xianyou Wendan,Hongwendan,Shatian Yu(Guangdong),Jinxiang you,Pingshan Yu and Sangma Yu were divided into Cluster?.2.Compared with BHT(SC5o=3.20mg/mL),EOs of Jinxiang Yu(SC50=4.07mg/mL)and Yuhuan Wendan(SC50=6.33mg/mL)exhibited the best radical scavenging abilities.The EOs from Liangping Yu demonstrated strong antimicrobial activities against different bacterna(MIC=250?g/mL),the EOs from Yuhuan Wendan showed much better antimicrobial activities against three Gram-negative bacteria.The EOs from Guanxi pinghe pomelo showed obvious antimicrobial activities against three Gram-positive bacteria.The EOs also had excellent a-glucosidase inhibitory activity,EOs from Pingshan Yu(IC50=0.001mg/mL),Jinxiang Yu(IC50=0.005mg/mL)and Yuhuan Wendan(IC50=0.011 mg/mL)showed better activities than acarbose(IC50=2.187mg/mL)and other samples.Xianyou Wendan(IC50=16.3?g/mL,32.3?g/mL)and Guanxi pinghe Yu(IC50=19.3?g/mL,32.9?g/mL)showed both significant cytotoxic against Huh7 cells and Hela cells,Liangping Yu(IC50=19.9?g/mL)and Yuhuan Wendan(IC50=20?g/mL)showed cytotoxicity against Huh7 cells.3.The total flavonoids content and the antioxidant and a-glucosidase inhibitory activities of the extract from 12 pomelo peels were determined for the first time.The results showed that the total flavonoids ranged from 9.193 to 13.771 mg/g.All samples were showed good antioxidant activities(DPPH,IC50=0.370-0.815 mg/mL.ABTS,3.333-6.467 mmol TE/100g.FRAP,2.533-5.467 mM Fe2+/100g)which analyzed by different methods.The extract of most pomelo peels demonstrated better a-glucosidase inhibitory activity than acarbose,Liangping Yu showed the best abilities(IC50=0.398 mg/mL).4.The adsorption properties of natural pomelo cellulose were tested.The adsorption of natural pomelo peels in oil-water system was selective adsorption,which oil adsorption firstly.The adsorption of diesel oil from 12 kinds of pomelo peels in simulated seawater satisfied the Lagergren pseudo-second-order kinetic equation.The desorption was in accordance with the Lagergren quasi-first-order kinetic equation.The adsorption/desorption equilibrium time was 10 min and 5 h,respectively.The amount of desorption was from 2.30 to 5.43 g/g,and the amount of desorption was from 0.22 g/g to 1.01 g/g.The removal rate of natural pomelo peel to diesel oil in the equilibrium time range was 14.21%-33.12%.The desorption rate of pomelo peel to diesel oil during desorption equilibrium was 9.87%-25.11%.Each sample showed good adsorption performance.The difference in adsorption and desorption performance was not obvious,and it was not directly related to the thickness of pomelo peel.This research provides preliminary scientific data for rational utilization of active compounds in pomelo peels and promotes green development for natural resource of pomelo peels.The result of research not only enriches the biomaterials sources of natural plant-derived compounds,but also reduces the waste of high-quality natural active substances,and more effectively alleviates the environmental burden caused by accumulation of pomelo peels.Finally,this study opens up a pratical way for comprehensive sustainable development of pomelo industry.