Mechanism Of Flavonoid To Penicillium Expansum On Antibacterial Ability

The infectious disease caused by Penicillium is the most serious disease during the storage of fruits and vegetables,while penicillium expansum(P.expansum)is the main pathogenic bacteria of Penicillium.The main methods of preventing Penicillium are physical control,chemical control and biological control.Biological control has become a hot spot in the field of preservation and storage of fruits and vegetables with the advantages of safety,innocuity,environmental protection and sustainability.Therefore,it is of great practical significance to develop green and efficient natural antibacterial agents for fruit storage.Ginkgo biloba is a kind of medicinal and edible plant,which has the active components such as flavonoids,polysaccharides and lactones.Ginkgo flavonoid has a good antibacterial ability,and its value has been studied by the researchers.The purpose of this paper was to study the antibacterial ability of Ginkgo flavonoid and the physiological index of P.expansum treated by Ginkgo flavonoid activity.The results were as follows:1.Penicillium was isolated from the apple which was infected by Penicillium and identified according to the micromorphology.2.Ginkgo biloba flavonoid was extracted from Ginkgo biloba by solvent extraction and purified by macroporous resin and polyamide column.The yield of crude flavonoids and pure flavonoids were 28%and 3.2%respectively.The purity.was determined by High Performance Liquid Chromatography(HPLC):the content of crude flavonoid in Ginkgo biloba leaves was 3.9μg/μL,and the content of fine flavonoid was 3.6μg/μL.3.From the Scanning Electronic Microscopy(SEM),the surface of Ginkgo flavonoids was smooth.Single peak appeared in the 200nm according to UV-visible spectroscopy and there were no any protein and nucleic acid components.Infrared spectrum detection of this substance showed that there were phenolic hydroxyl,-OCH3,benzene,-C=O and glucose.4.The effective inhibitory concentration of Ginkgo flavonoid was determined by P.expansum growth situation.The results showed that,with the over 40%ethanol concentration dissolved 70mg/mL Ginkgo flavones,the inhibitory effect was obvious.5.When the concentration of ethanol was 40%and the concentration of flavonoids was 70mg/mL,the bacteriostatic mechanism was researched.The trend of cell membrane permeability:the effect of conductivity of mycelium of P.expansum dealed with the flavonoids of Ginkgo biloba showed a rising trend,while the control group was almost not much fluctuation,which suggested that flavonoids have ability to cell lysis.The trend of lipid oxidation:the content of Malondialdehyde(MDA)in the control group increased at the initial stage and then decreased,and the MDA in the flavonoid group increased first,then decreased and then increased again.The degree of membrane lipid oxidation of P.expansum treated with flavonoids was 2.12-fold comparing with that in the control group.The change of protein content:The two groups of proteins showed a downward trend,and the reduction of protein in the treatment group was about 1.5-fold lower than that of the control group.Analysis of resistance enzyme activity:Superoxide dismutase(SOD),Catalase(CAT),Polyphenylene Oxide(PPO)and Peroxidase(POD)arriveded to the peak and then declined.Due to P.expansum interfered by outside conditions,these resistance enzymes did a resistance to adversity and protected themselves.With Ginkgo flavonoid continuous inhibiting P.expansum,the enzyme activities decreased,and the protective effect on P.expansum was lower,which reflected the inhibitory effect of flavonoid of Ginkgo biloba on P.expansum.Apple without any damage,do tests of stab for the group infected by P.expansum,the blank group,the flavonoids treat group without infections,and the flavonoids treat group infected by P.expansum.The inhibitory effect of Ginkgo flavonoids on apple was studied according to three parameters weight loss,peel fold and color depth.The weight loss was in the order of the following:the P.expansum group>the blank group>the flavonoids treat group infected by P.expansum>the flavonoids treat group without infections.From the degree of peel fold,the largest degree of wrinkle was the flavonoids treat group without infections,followed by the blank group,the flavonoids treat group infected by P.expansum,the groupinfected by P.expansum.From the deep to shallow of color:the group infected by P.expansum>the blank group>the flavonoids treat group infected by P.expansum>the flavonoids treat group without infections.The results indicated that flavonoids have the effect of maintaining fruit quality.