68(P-53) ラン藻Nodularia PCC7804株が生産するノジュラリン類似体、ノジュラリン-Harの単離および構造決定(ポスター発表の部)

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Cyanobacterial hepatotoxin, microcystins and nodularins, are potent, and make troubles in eutrophic lake and marine water body. The toxic activities are same as "okadaic acid class cancer promoter". Over 60 homologues of microcystins are reported up to date, and some homologous nodularins are also reported. Toxicity of those homologues are greatly different in their chemical type. Since the homologues are considered increasing in future, it is consequently essential that the toxins are analyzed by isolation followed by toxicity assay (i.e. mouse bioassay) yet. In this study, the structure of nodularin-like substance, nodularin-Har (1) derived from Nodularia PCC7804 was determined by mainly 2D NMR spectroscopy and FAB mass spectrometry 1 was isolated by liquid chromatography, and showed severe hepatotoxicity to mouse (LD_<50>=70μg/kg, i.p.). UV spectrum of 1 was completely concordant with that of nodularin, and therefore it was thought that 1 has conjugated double bond in Adda and Mdhb. The molecular weight determined by FAB-MS was, however, larger for 14 Da than nodularin. Thus, 1 can be considered that methyl or methylen is added to nodularin. However, ^1H-NMR spectrum did not show any methyl peak supplementary to nodularin, therefore that methylen is added to nodularin was concluded. 2D NMR analyses including H,H-COSY, H,H-TOCSY, HMBC, and HSQC showed changing from arginine residue in nodularin to homoarginine (Fig. 2). This decision was supported by FAB-MS spectrum which showed a 84m/z iminonium fragment ion peak originated from homoarginine, and a 135m/z peak from Adda (Fig. 3). All ^1H and ^<13>C could be assigned by 2D NMR analyses (Table). Nodularin was not detected from PCC7804 while nodularin-Har was produced relatively large deal. Arginine is not contained in this toxin, but homoarginine, is a matter of considerable interest.
天然有機化合物討論会の論文
2000-10-01

68(P-53) ラン藻Nodularia PCC7804株が生産するノジュラリン類似体、ノジュラリン-Harの単離および構造決定(ポスター発表の部)

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