Studies On Antimicrobial Activity Of Endophytes From Several Plants

We report here the isolation, purification, and identification of microorganism strains,as well as the evaluation of antimicrobial activity and identification of active ingredients ofthe metabolites of preferred strains. The main results are as follows:Taking different separating culture medium and isolating methods,64strains ofendophytic fungus and61strains of actinomycetes were separated from the leaf, stem, rootof several plant.The metabolite of the above mentioned microorganisms was subjected to evaluate theirantibacterial activity by diffusion method and their antifungal activity by the method ofmycelial growth.A strain of F52was isolated from the Vigna unguiculata （Linn.） Walp. It wasidentified as Aspergillus flavus F52according to morphological characteristics and ITSregion of rDNA. A compound, named XN-01, was obtained from the fermentation broth ofAspergillus flavus F52by extraction with ethyl acetate and recrystallization with alcohol.The structure of XN-01was elucidated as kojic acid by the means of NMR, HR-ESI/MSand IR. Considering the high and mono-component, the fermentation conditions ofAspergillus flavus F52were optimized. The content of kojic acid will be24.44g/L at12days when addtion of glucose （20g/L）and sucrose（40g/L）.In a program of screening antibiotics from natural products, an antifungal ingredient wasobtained from the fermentation broth of Colletotrichum orbiculare by the procedure ofmacroporous resin extraction and silica column chromatography. Its chemical structure waselucidated by the techniques of HR-ESI MS, NMR and IR, and its antifungal activities againstB. cinerea, F. oxysporum, A. alternata，C. gloesporioides and C. lunata were evaluated bythe methods of inhibition of spore germination and mycelium growth, respectively. Theresults indicated that the active ingredient was radiciol, a member of resorcylic acid lactonefamily. Rediciol could not inhibit the spore germination of all tested fungi, whereas it showedstrong inhibitory activity against mycelial growth of B. cinerea.