Fusaricidins B, C and D, new depsipeptide antibiotics produced by Bacillus polymyxa KT-8: isolation, structure elucidation and biological activity

Fusaricidins B, C and D, new depsipeptide antibiotics, have been isolated as minor components from the culture broth of Bacillus polymyxa KT-8 which was obtained from the rhizosphere of garlic suffering from the basal rot caused by Fusarium oxysporum. The structure of fusaricidin B has been elucidated mainly by various NMR experiments coupled with amino acid analysis in relation to fusaricidin A, the main component of the complex, whose structure was reported previously. The fraction consisting of fusaricidins C and D was unsuccessfully separated, giving roughly a 4:1 mixture of the two, respectively. The structures of fusaricidins C and D have been determined within the mixture by detailed analyses of the 2D NMR spectra. Fusaricidins B, C and D are active against fungi and Gram-positive bacteria almost as well as fusaricidin A.