98(P44) 粘液細菌Cystobacter fuscusから得られた新規抗菌性物質cystothiazole類の構造と生物活性(ポスター発表の部)

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In recent years a number of novel secondary metabolites have been discovered from myxobacteria, which have now recognized as a rich source of novel bioactive compounds. During the course of our search for myxobacterial metabolites which exhibited inhibitory activity against the phytopathogenic fungus Phytophthora capsici, we isolated seven active compounds named cystothiazoles A-G (1-7) from the myxobacterium Cystobacter fuscus. The structural elucidation was accomplished by spectroscopic analyses and chemical derivatization. Molecular formulas of 1-7 were determined from high resolution FABMS. ^1H, ^<13>C-NMR and HETCOR spectra of 1 suggested partial structures including a bithiazole unit, and the HMBC correlations disclosed the connectivities of these partial structures to give the gross structure of 1. The E geometry of the double bond at C-2 was evidenced by NOE data (H-2/3-OMe). Ozonolysis of 1 followed by methylation gave known 9, revealing the absolute stereochemistry of 1. The gross structures of the other derivatives were elucidated by comparing the spectral data with those for 1. The absolute stereochemistry of 3 was confirmed by methylation of 3 under basic conditons to give 1. The stereochemistry of the other derivatives were estimated by the comparison of ^1H-NMR data and specific rotation with those of 1 or 3, but that of 5 is still unclear. The antifungal activity of 1-7 against P. capsici was evaluated by a paper disc method. The activity decreased in the order 1≈7>6>2>3≈4≈5 (Table 2), indicating that the β-methoxy-α,β-unsaturated ester and 5-methoxyl group seemed to be important for the activity. The antimicrobial spectrum of 1 was summarized in Table 3 in comparison with myxothiazol (8). 1 was active against all molds and yeasts tested, but had no effect on bacteria. Although such a tendency of activity was same as that of 8, the potency of 1 was higher. Furthermore, 1 exhibited one tenth cytotoxicity of 8. The mode of action of 1 is proved to be blocking of respiration, because 1 inhibited NADH oxidation of submitochondrial membrane fraction as in the case of 8 as shown in Figure 3.
天然有機化合物討論会の論文
1999-09-01

98(P44) 粘液細菌Cystobacter fuscusから得られた新規抗菌性物質cystothiazole類の構造と生物活性(ポスター発表の部)

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