Isolation of anteiso-C17, iso-C17, iso-C16, and iso-C15 Bacillomycin D from Bacillus amyloliquefaciens SD-32 and Their Antifungal Activities against Plant Pathogens

Two new cyclic lipopeptides (3 and 4) were isolated from the culture filtrate of Bacillus amyloliquefaciens strain SD-32, together with two known metabolites, iso-C-15 and iso-C-16 bacillomycin D (1 and 2). Spectroscopic and chemical analyses identified the structures of the new compounds 3 and 4 as anteiso-C-17 bacillomycin D, cyclic (L-Asn-o-Tyr-D-Asn-t-Pro-t-Glu-D-Ser-L-Thr-3-amino-14-methylhexadecanoic acid) and iso-C-17 bacillomyc-in D, cyclic (L-Asn-o-Tyr-n-Asn-L-Pro-L-Glu-o-Ser-t-Thr-3-antino-15-methylhexadecanoic acid), respectively. The absolute configuration of C-3 in the beta-amino fatty acid was determined to be R on the basis of the CD spectrum of its dinitrophenyl-p-methoxyaniline derivative. The activities of compounds 1-4 were evaluated against 13 plant pathogens: the activities of anteiso- and iso-C-17 bacillomycin D (3 and 4) were almost the same and stronger than those of iso-C-15 and iso-C-16 bacillomycin D (1 and 2); iso-C-15 bacillomycin D (1) was weakest. Compounds 2-4 inhibited the growth of all fungi tested; however, Pythium aphanidermatum was not inhibited at all by any of the compounds. Furthermore, compounds 1-4 at concentrations of 80, 40, 30, and 30 mu M, respectively, inhibited completely the Botrytis cinerea infection in cucumber leaf.