77. イネフィトアレキシンモミラクトンBのいもち病菌による代謝産物の同定(口頭発表,植物化学調節学会第46回大会)

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Phytoalexins (PAs) are low-molecular-weight antimicrobial compounds accumulated in plants after exposure to pathogen. On the other hand, pathogenic microbes can prevent plant disease resistance mechanism including PAs. In the previous report, we identified the main metabolite of momilactone A by rice blast fungus was 3,6-dioxo-19-nor-9β-pimara-7,15-diene. In this study, we investigated the metabolism of momilactone B, which has higher antifungal activity than momilactone A, by blast fungus. The concentration of momilactone B decreased during incubation in suspension culture of blast fungus containing momilactone B at an initial concentration of 100 ppm. Accompanying momilactone B decrease, the accumulation of a substance (designated as M302) which showed a possible molecular-related ion ([M+H]^+) at m/z 303 was detected in LC/MS analysis. Momilactone B metabolites were extracted with 70% methanol from 160 ml of fungal culture medium incubated 4 h after the addition of momilactone B (10 mg). The aqueous solution was partitioned against ethyl acetate, and the combined ethyl acetate layer was evaporated to dryness. Finally, M302 (1.34 mg) was separated by a reversed-phase HPLC. HRMS indicated a molecular formula of C_<19>H_<26>O_3. However, 1D NMR spectra revealed that the M302 included a minor analog of M302. Now we are trying to isolate M302 and to elucidate its structure.
2011-10-03