Isolation,identification,and antimicrobial activity of metabolites from Aschersonia marginata(Ascomycota,Clavicipitaceae)
[Aim]Aschersonia is a genus of insect pathogenic fungi used for the control of whiteflies and scale insects.The metabo-lites of the fungi have antibacterial,insecticidal,anti-tumor,antioxidant,and other biological activities.This study aim to isolate and identify the metabolites in the fermentation of A.marginata,and test their antibacterial activity,so as to provide the basis for expanding the application of this biocontrol bacteria.[Method]Chromatographic techniques and spectroscopic methods were used to isolate and identify compounds from fermented cultures of A.marginata WYTF2017-01.The activities of identified components a-gainst fungal and bacterial pathogens were evaluated.[Result]Twelve compounds were isolated from A.marginata WYTF2017-01 cultures,which included methyl 24-methylene-3-oxolanost-8-en-26-oic ester(1),ergosta-5,7,22-trien-3-ol,4-methyl-,(3β,4α,22E)(2),dustanin(3),3β-acetoxy-15a,22-dihydroxyhopane(4),ergosterol(5),4-(hydroxymethyl)-3-furancarboxylic acid(6),eupenicisirenin B(7),4,6-dihydroxy-1(3H)-isobenzofuranone(8),β-sitosterol(9),methyl 4-tert-butylbenzoate(10),2-benzyl-4H-pyran-4-one(11),and 6-benzyl-4-oxo-4H-pyran-3-carboxamide(12),in which compounds 1,2,and 6-12 were firstly identified from entomopathogenic fungi.Compounds 1,2,3,6,7,8,11,and 12 displayed antifungal or antibacterial activities to varying degrees,with MIC(minimal inhibitory concentration)values of 3.13-50.00 μg·mL-1.Relatively higher antibacterial ac-tivities were observed for compounds 7,8,and 12,in which the activity of compound 7 against Escherichia coli was comparable with that of streptomycin,with an MIC value of 3.13 μg·mL-1.Compounds 8 and 12 displayed high antibacterial activities against Ral-stonia solanacearum,with MIC values of 6.25 and 12.50 μg·mL-1,respectively,which were better than or comparable to positive control streptomycin(MIC=12.50 μg·mL-1).[Conclusion]Some compounds isolated from A.marginata WYTF2017-01 showed antifungal and/or antibacterial activities,indicating their potential for biocontrol of plant diseases.
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