Studies On The Secondary Metabolites Of Strain Nigrospora SP.NY03 And Its Antifungal Activity

Endophytic fungi have been recognized as a potential source of bioactive secondary metabolites.A large number of secondary metabolites from endophytic fungi have been successfully separated which have various biological activities.It provides a new idea for the research of new drugs.Therefore,the endophyte and its metabolites have a great value on application prospect.In this paper,a total of 229 endophytic fungi were isolated and purified from plants.25 endophytic fungi were selected and the antifungal activity of their ethyl acetate crude extract of fermentation broth against Rhizoctonia solani,Sclerotinia sclerotiorum and Fusarium graminearum was performed.Strain NY03 diaplayed good activity against all kinds of the selected plant pathogens.Besides,The PDA culturation was determined as the best method by testing the yield and the antifungal activity of crude extract under different culture conditions.Strain NY03 was identified as Nigrospora sphaerica by morphology and molecular biology.Among the different organic crude extracts from the PDA culturation of Nigrospora sphaerica(strain NY03),the antifungal activity indicated that the crude extract of dichloromethane and ethyl acetate had a better activity.Seven known compounds were obtained from these two organic crude extracts,which were griseofulvin(1)?dechlorogriseofulvin(2)?austrocortinin(3)?emodin(4)?methyl3-chloro-6-hydroxy-2-(4-hydroxy-2-methoxy-6-methylphenoxy)-4-me-thoxy-benzoate(5)?epigriseofulvin(6)and griseoxanthone C(7)respectively.Compound 1 and 6 can significantly inhibit the growth of plant pathogenic fungi,the activity against R.cerealis is the best which is better than the positive control carbendazim.The protective efficacy of compound 1 and 6(50 mg/mL)on Rhizoctonia cerealis infection prevention were better than the positive control validamycin(100 mg/mL).Besides,the protective efficacy of compound 1 and 6(500 mg/mL)on Sclerotinia sclerotiorum infection prevention were all comparable to the positive control carbendazim(250 mg/mL).In summary,the secondary metabolites of Nigrospora sphaerica have great application prospects in the prevention and control of plant diseases.In addition,the effect of halogen ions on griseofulvin analogues biosynthesis was preliminary studied in this paper.The results showed that the griseofulvin could not be synthesized with the absence of chloride.When cultured medium contained bromide and iodide,griseofulvin halogenated analogues could be detected.