Isolation and structural characterization of polymyxin B components

Polymyxin B is a peptide antibiotic complex present as sulphate. The components were separated preparatively on a poly(styrene-divinylbenzene) (PLRP-S), 1000 Angstrom, 8 mum, 250x12.5 mm I.D. stationary phase maintained at 60 degreesC and using 215 nm detection. Elution was carried out with acetonitrile-sodium sulphate solution (0.7%, m/v; pH adjusted to 2.5 with trifluoroacetic acid)-water (18:50:32, v/v) at a flow-rate of 4.0 ml/min. Seven polymyxin B components were isolated and characterized using H-1 and C-13 NMR. The molecular masses were confirmed by mass spectrometry. The structures of two components were determined for the first time. Polymyxins B-5 and B-6 were identified as having the same composition as polymyxin B-1 except that the fatty acid moiety was nonanoic acid and 3-hydroxy-6-methyloctanoic acid, respectively. (C) 2001 Published by Elsevier Science B.V.