Identities of the Fatty Acids derived from the Polymyxins and Colistin

Abstract

Hausmann and Craig¹ first demonstrated that the peptide antibiotic polymyxin B was not homogeneous but could be separated by counter-current distribution into two components, polymyxin B1 and polymyxin B2. On hydrolysis, in addition to the amino-acids αγ-diamino-butyric acid, leucine, phenylalanine and threonine, polymyxin B1 gave (+) 6-methyloctanoic acid, which had previously been isolated and characterized by Wilkinson². Polymyxin B2, although containing the same amino-acids gave an optically inactive acid, C₈H₁₆O₂, not identical with n-octanoic acid but which was not otherwise characterized.