Cairomycin B

Cairomycin B in the fermentation broths of Streptomyces sp. strain AS-C-19 accompanied cairomycin A and cairomycin C. The cairomycins are peptides with potent activity against gram-positive bacteria. On acid hydrolysis, cairomycin A yielded valine and aspartic acid, whereas cairomycin C yielded lysine, glycine, valine, leucine, and aspartic acid, as identified by paper and gas chromatography. These amino acids were found to exist in their alpha-L form. Cairomycin A was tentatively assigned a 6-isopropyl-2,5-diketopiperazine-3-acetic acid structure. The three cairomycins were distinct from each other in their ultraviolet, infrared, and mass spectra; elemental analyses; and their chromatographic behavior in different developing solvents.

Cairomycin B is a new cyclic peptide antibiotic that was isolated from Streptomyces As-C-19 obtained from the soil of Cairo. The antibiotic had the following empirical formula: C(10)H(15)N(3)O(3); on acid hydrolysis, it yielded aspartic acid and lysine. Spectral analysis and its chemical characteristics indicated that it was a cyclic peptide. The antibiotic melted at 120 to 121 degrees C and was freely soluble in chloroform, ethyl acetate, and acetone, slightly soluble in alcohols, and rather insoluble in water and petroleum ether. Cairomycin B was mainly active against gram-positive bacteria, with high toxicity to experimental animals and weak serum-binding properties.