Efficient Separation Of Psidium Guajava Leaf Essential Oil,Polysaccharides And Inhibitory Activity Of Essential Oil-polysaccharides Complexes Against Fusarium Spp

Psidium guajava L.belongs to the Myrtaceae family,which is rich in resources with grow ing all over southern China.The leaves of P.guajava L.contain essential oils,flavonoids,poly saccharides and other biologically active secondary metabolites with a variety of biological acti vities.It is used to treat various diseases all over the world.In order to make full use of the leaf resources,this paper uses them as experimental materials to establish a green and efficient mic rowave-assisted one-pot hydrodistillation extraction method(MAHE)to extract and separate it s essential oils and polysaccharides were extracted by single factor and response surface optimi zation method to optimize the extraction process,and the extracted essential oils were used for medicinal herbs Astragalus pathogenic Fusarium(F.avenaceum,F.sambucinum,F.trichotheci oides and F.culmorum),using crude polysaccharides from leaves of P.guajava L.and sodium caseinate as wall materials and P.guajava L.leaves essential oil as core materials,the P.guaja va L.leaves essential oil-polysaccharides complex was prepared by the complex coacervation method,and the optimal conditions for encapsulation of the complex were obtained by single f actor experiment and Doehlert design,and its physicochemical characterization was performed.Addition,Inhibitory effect on the above-mentioned Fusarium before and after about P.guajav a L.essential oil.Its important contents are as follows:1.The essential oil and polysaccharides were extracted by microwave-assisted one-pot hy drodistillation extraction.The solvent used in the experiment was 30% PEG600 obtained by sin gle-factor experiments.By using the first-order kinetic model and BBD and RSM operating par ameters to optimize,the optimal process conditions were: The liquid-solid ratio was 7.4 m L/g,the microwave irradiation power was 630 W,and the microwave irradiation time was 42 min.Under the optimized conditions,the yields of essential oil and polysaccharides of MAHE were31.50±1.35 m L/kg and 302.0±13.3 g/kg,respectively.The developed MAHE method can not o nly extract polysaccharides and essential oil at the same time,but also had a high yield and a sh ort time.In addition,the GC-MS results showed that there was no significant change in the co mposition of the essential oil,and the main chemical components of the essential oil were cary ophyllene,calamenene A,nerolidyl acetate and humulene epoxide.From the perspective of en vironmental impact and economic benefits,MAHE was found to emit less carbon dioxide into t he atmosphere and consume less energy.2.To explore the inhibitory activity of P.guajava L.essential oil on Fusarium,using the a gar diffusion method and the cross method to analyze the antibacterial effect,on the medium c ontaining P.guajava L.leaves essential oil,the four kinds of Fusarium colonies showed slow g rowth and the number of colony spores decrease,the colonies tend to become smaller.In additi on,the minimum inhibitory concentration(MIC),minimum killing concentration(MBC)of P.guajava L.leaves essential oil against four Fusarium species,time lethality curve analysis,min imum inhibitory concentration(MIC)of four Fusarium species(F.avenaceum,F.sambucinum,F.trichothecioides and F.culmorum)were 1.00 mg/m L,1.75 mg/m L,1.0 mg/m L and 2 mg/m L,respectively,of which the F.avenaceum and F.sambucinum were more sensitive than the oth er two.The results showed that P.guajava L.leaves essential oil had a bacteriostatic effect on Fusarium and can inhibit the growth and development of mycelium.3.The P.guajava L.leaves essential oil-polysaccharides complexes were prepared by usin g the complex coacervation method,using P.guajava L.leaves crude polysaccharides and sodi um caseinate as the wall material and P.guajava L.leaves essential oil as the core material.Th e optimal preparation process of the polysaccharides complexes,physical and chemical charact erization and antibacterial experiments of the complexes were carried out,and the final prepara tion conditions of the complexes were as follows: the ratio of wall to material was 1:2,the ratio of core to wall was 1:2.25,and the ionic strength was 1.1mol/ L,the reaction time was 15 min,the tannic acid content was 20%,the obtained encapsulation efficiency was 97.18%,The enca psulation rate of the complexes was 75.79%,the oil content was 36.28%,and the polysaccharid es content in the wall material was 35.71% and the average particle size was 425 ±1.55 nm.Th e morphology and structure of P.guajava L.leaves essential oil-polysaccharides complexes we re analyzed by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR)and thermogravimetry(TG).FTIR showed that crude P.guajava L.leaves essential oilpolysaccharides and sodium caseinate were electrostatically bound formed by physical action.The TG and DTG curves show that,compared with the P.guajava L.leaves essential oil-polys accharides complexes and essential oil which before and after encapsulation,the peak value of thermal weight loss lagged behind,indicated that the thermal volatilization of the essential oil s lowed down and played a slow-release role.The SEM observation results showed that P.guaja va L.leaves essential oil-polysaccharides complexes had a regular surface structure and a unifo rm wall material,which were spherical in shape.In addition,the difference in antibacterial acti vity of P.guajava L.leaves essential oil-polysaccharides complexes and essential oil which bef ore and after encapsulation was evaluated by comparing the diameter of the inhibition zone.Th e results showed that the antibacterial effect of P.guajava L.leaves essential oil-polysaccharide s complex essential oil on F.avenaceum,F.sambucinum,F.trichothecioides and F.culmorum was significantly better than that before embedding,which also showed that the prepared micro bes had better antibacterial effect,and it was slow-release.The experimental research results of the paper provide a direction for the further develop ment and utilization of P.guajava L.leaves,which not only provides a green and efficient extra ction method,but also provide new ideas for the further development of slow-release bacteriost atic agents based on plant essential oils and application of crude polysaccharides as novel mate rials in composites.Converting essential oils from liquid to solid powder reduces the limitation s of volatility,easy oxidation and photodegradability of essential oil in specific applications,an d has a positive social impact on the development and utilization of essential oils.