Studies On The Monoamine Oxidase Inhibitory Activity Of The Fungal Secondary Metabolites

Endophyte are fungal microorganisms which reside in the host plant tissuesintercellularly or intracellularly without causing any apparent infection symptoms. Inthe long-term symbiosis with the host plant, endophytic fungi secret plethorametabolites which have broad biological activity, such as antibacterial, antiviral,antioxidation, anticancer, immunesuppression, to provide a valuable resource to thedevelopment of new bioactive natural products.Monoamine oxidase (MAO) play an important role in metabolism ofneurotransmitters. When the activity of MAO is abnormally elevated, it will affectdepression and neurodegenerative diseases like Parkinson’s and Alzheimer’s. Theselective MAO inhibitors are important drug targets for the treatment of depressionand neurodegenerative diseases. Researchers have found a variety of selective MAOinhibitors from natural products. This natural products have potential to be newtherapeutic leads for depression, Parkinson’s and Alzheimer’s. However, most of thenatural MAO inhibitors reported had been resourced from plants, it is rarely reportedMAO inhibitors spaced from microorganisms. Therefore, screening natural MAOinhibitors from endophyte metabolites. has broad prospects.In this study,147endophytic fungi are isolated from17kinds of medicinalplants, belonging to14genera, of which the largest number of three genera wereAspergillus, Fusarium and Alternaria.There are ethyl acetate extract and n-butanol extract of147endophytic fungifermentation broth for screening MAO inhibitors from endophyte metabolites.Onlyfive strains showed potent MAO inhibitory activity,with the inhibitory rate of greaterthan50%, of which three strains with the IC50of nearly200μg/ml. The strain E160isolated from Hypericum ascyron L. has been as a folloe up study. Throngmorphological and molecular biology method, the strain was identified as Aspergillusfumigatus.This study scaled up the solid fermentation of strain E160,and got8.7g of theethyl acetate extract. This ethyl acetate extract showed the potent MAO inhibitory activity with the IC50of195.1μg/ml. The MAO inhibitory chemical constituents wasisolated through bioassay-guided fractionation. by silica gel column chromatographyand ODS column chromatography. The MAO inhibitory components EM10-2withthe IC50of51.1μg/ml. The compents EM10-2with the IC50for MAO A and MAO Bwere101.0μg/ml.and22.7μg/ml, showed to be slightly selective towards MAO B,and it has potential to be selective MAO inhibitors.In order to improve the activity of MAO inhibitory, the isolate Aspergillusfumigatus.E160fermentation conditions were optimized. We culture the strain E160in different nutritional environment and culture condition, and by measuring theinhibitory rate to MAO and the weight of the ethyl acetate extract to make sureoptimal condition for MAO inhibitors production. This study discussed the influenceof the carbon, nitrogen, pH value, inoculum size, bottling size, fermentationtemperature and fermentation time. In the end,we determined the best conditions forthe fermentation medium:2%glucose,2%yeast extract,0.05%magnesium sulfate,0.1%potassium dihydrogen phosphate, pH value0f6.0, containing40%medium ofthe conical flask, inoculated2%（v/v）1×107CFU/ml spore suspension,25℃cultured11d. Under this condition, the weight of the ethyl acetate extract could up to25.9mg,compared with49.7%before optimization; and the inhibitory rate to MAOcould up to72.8%,,compared with25.7%before optimization.The result of the study could provide resource strains and make the foundationfor theory and experiment for the screening of MAO inhibitors from endophytemetabolites...