Study On The Bioactive Compounds In Gannan Navel Orange Peel Fermentated By Penicillium Polonicum

Gannan navel orange is a special fruit in Ganzhou,Jiangxi Province.It is also a national geographic indication product of China.Its annual output is up to one million tons in recent years.In this thesis,the transformation of functional active components of Gannan navel orange peel fermented by Penicillium polonicum(P.polonicum)was comprehensively investigated.By comparing the chemical constituents and biological activities of orange peel before and after fermentation,together with the production of secondary metabolites by P.polonicum in rice medium,the mechanism of the transformation of functional active components from the Gannan navel orange peel was preliminarily illuminated.The specific research content and results of this study are as follows:1.Effects of the fermentation on chemical constituents and biological activities of extracts from Gannan navel orange peel by P.polonicum.The TPC and TFC of fermented orange peel ethanol extract(FEE)were more than 6 times higher than the unfermented orange peel ethanol extract(EE).The TPC and TFC of orange peel extract before and after fermentation showed that P.polonicum fermentation significantly increased the chemical composition of Gannan navel orange peel extract.In terms of antibacterial activity test,MIC of anti-MRSA and anti-Xcc in FEE were 32 and 16 times stronger than EE.The antioxidant capacity in FEE were nearly 14 times higher than the EE.Meanwhile,the antiglycation activity of FEE was nearly 3 times higher than that of EE.As for the α-glucosidase inhibition effect,FEE was nearly 2 times stronger than EE.The results showed that fermentated by P.polonicum significantly increased the antibacterial,antioxidant,antiglycation and ɑ-glycosidase inhibitation activities of orange peel extracts.2.Study on the chemical constituents and biological activities of secondary metabolites from Gannan navel orange peel by P.polonicum fermentation: In total,28 compounds were isolated from the orange peel extract fermented by P.polonicum,involving three flavonoid glycosides(FGs),narirutin(1),hesperidin(2)and didymin(3),ten polymethoxyflavone(PFMs),isosinensetin(4),3,3’,4’,5,7,8-hexamethoxyflavone(5),sinensetin(6),4’,5,7,8-tetramethoxyflavone(7),3,3’,4’,5,6,7-hexamethoxyflavone(8),nobiletin(9),4’,5,6,7-tetramethoxyflavone(10),3,3’,4’,5,6,7,8-heptamethoxyflavone(11),5-hydroxy-6,7,3’,4’-tetramethoxyflavone(12),tangeretin(13),4’-hydroxy-5,6,7-trimethoxyflavone(14).In addition,three other flavonoids,naringenin(15),hesperetin(16),isosakuranetin(17)and zanthopyranone(19),and three limonoid compounds,limonin(18),nomilin(20),methyl nomilinate(21),two sterol compounds,ergosterol(23),cholesterol(28),and four other compounds,kojic acid(24),anthopyranone(25),jasmonol E(26),1,2-dihydroxylimonene(27),were isolated and elucidated.HPLC analysis showed that compounds15-17 were unique peaks in FEE.Some compounds were subjected to the evaluation of biological activities,and the results showed that compounds 15,16 and 17 had good biological activities.3.Effects of fermentation time on chemical constituents and biological activities in FEE.The TPC and TFC of FEE increased significantly with the increase of fermentation time,so do the biological effects involving antibacterial,antioxidant,antiglycation and ɑ-glycosidase inhibitation.Based on the chemical composition differences of orange peel before and after fermentation,compounds 15,16 and 17 were speculated to be obtained by the hydrolysis of glycosidic bond of compounds 1,2 and 3.Therefore,this study also carried out the study on the extraction and preparation of glycosidic hydrolase from orange peel by P.polonicum fermention,and confirmed that β-glucosidase was produced during the fermentation of orange peel by P.polonicum.4.Chemical composition of secondary metabolites from P.polonicum: In order to study whether P.polonicum produces mycotoxins during orange peel fermentation,the secondary metabolites of P.polonicum in rice medium were isolated.Hence,there were eight compounds isolated from secondary metabolites of P.polonicum with the rice medium.They were ergosterol(Ⅰ),3-O-methylviridicatin(Ⅱ),viridicatol(Ⅲ),Cyclo(L-Trp-L-Phe)(Ⅳ),(2E,4E)-5-((2S,3S,4R,5R)-3,4-dihydroxy-2,4,5-trimethyltetrahydrofuran-2-yl)-2,4-dimethylpenta-2,4-diena l(Ⅴ),6-acetyl-4-methoxy-3,5-dimethyl-2H-pyran-2-one(Ⅵ),penicyrone B(Ⅶ),aurantiogrisidinol(Ⅷ).Compounds Ⅱ,Ⅲ,Ⅳ of PEE had good antibacterial effects.HPLC analysis showed that the secondary metabolites of P.polonicum fermented in orange peel and rice medium were not the same.In conclusion,this study showed that the glycoside hydrolase was produced during the fermented the orange peel by P.polonicum,which hydrolyzed flavonoid glycosides in orange peel to aglycones,thus resulting in the enrichment of functional flavonids and the enhancement of biological activity of the fermented orange peel extract.HPLC analysis showed that the fermented orange peel did not contain secondary metabolites produced by P.polonicum in rice medium,indicating that P.polonicum had different pathway of producing secondary metabolites in orange peel and rice substrate.The results provided some basis information for the value-added utilization of navel orange peel.