Lonomycins B and C, two new components of polyether antibiotics. Fermentation, isolation and characterization

Lonomycin B (II), C44H75O14Na, m.p. 181-182 degrees C, and lonomycin C (III), C43H73O14Na, m.p 186-187 degrees C, were isolated as their sodium salts from the fermentation broth of Streptomyces ribosidificus TM-481. Their physicochemical properties demonstrated that II and III are closely related congeners of lonomycin A (I). The identical mass spectra of methyl esters of I and II indicated that II is a stereoisomer of I. On the other hand, the mass spectrum of a methyl ester of III showed a peak at m/e 810 due to M+-H2O which is smaller by 14 mass units than the maximum peak at m/e 824 due to M+-H2O of the methyl esters of I and II. This result together with the elemental analysis strongly suggested that III is a demethyl derivative of I or II. II and III are slightly less active than I in their antimicrobial activities.