| The culture broth of marine actinomycete sp. Y12-26 has a strong inhibitory effect on a variety of plant pathogenic fungus, such as Botrytis cinerea, Pyricularia oryzae and Rhizoctonia solani. Since the active substance content is very low, requirements on preliminary exploration and optimization the shaking fermentation conditions to increase the accumulation of the active substance in the fermentation broth that enough to further steps of purification and refinement and elucidate the structure.In this experiment, by tracking the biological activity for the rice blast fungus as a analysis tools, through pre-fermentation, extraction, silica gel column chromatography, preparative thin layer chromatography, HPLC and other purification techniques, we get three antifungal active ingredient A1, B1 and C2. By high resolution mass spectrometry analysis, the formula of compound A1 was confirmed as C27H30O12 with a molecular weight of 546.1825; The formula of compound B1 was confirmed as C48H74O14N12 with a molecular weight of 1042.5524; The formula of compound C was confirmed as C7H7O2N with a molecular weight of 137.0549. Scan the three pure compound A1, B1 and C by 1H-NMR, 13C-NMR, DEPT 135,2D-NMR (1H-1H COSY, HSQC, HMBC, NOESY) and elucidate its structure. On the basis of spectral data, their structure were identified as Daidzein-4’,7-di-a-L-rhamnoside(Al),Iturin A-2(B1),Salicylamide(C2).The three pure substances were carried on antifungal activity spectrum to plant pathogenic fungus such as Botriytis cinerea, Rice Blast Pathogens, Gibberella, Rhizoctonia solani, Helminthosporium maydis in vitro. Through the bioassay, we found that compounds A1 had a good inhibitory effect on Botriytis cinerea and its MIC against B. cinerea were 125μg/mL. Compound B1 had a broad-spectrum antifungal activity, its MIC against B. cinerea and R. solani. were 12.5μg/mL. The MIC of compound C2 against B. cinerea was 125μg/mL. |
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