Structure-Activity Relationship of Colistins.

Abstract

Purified samples of polymyxin group antibiotics were effective antimicrobial agents against Escherichia coli. Removal of the C9-fatty acid from the colistin molecule resulted in the decrease of the activity. The side chain moiety itself showed no antimicrobial activity. The cyclic peptide moiety showed an antimicrobial activity although it was less active than the parent antibiotic. The active structure responsible for the antimicrobial activity is the cyclic peptide moiety in colistin molecule.