Isolation of novel anti-TB cyclohexapeptides from actinomycetes

• Published in: Planta Medica
• Main Authors: Cai, G, Napolitano, JG, McAlpine, J, Cho, S, Wang, Y, Jaki, BU, Suh, JW, Yang, SH, Lee, IA, Pauli, GF, Franzblau, SG
• Format: Conference Proceeding
• Language: English
• Published: 19.07.2012
• DOI: 10.1055/s-0032-1320753
• ISSN: 0032-0943

Thirty-five thousand actinomycete extracts were screened for anti-TB activity, followed by C 18 cartridge fractionation of 37 prioritized extracts. Based on MICs against replicating and non-replicating M. tuberculosis (Mtb), and IC 50 s against Vero cells to generate selectivity indices, seven fractions were selected for further separation. ECUM14046, a Streptomyces hygroscopicus strain, when cultured in GSS media and extracted with ethyl acetate, yielded a fraction with potent anti-TB activity. This fraction had a well-defined thin layer chromatography (TLC) profile and was therefore further fractionated using preparative HPLC. The molecular formulas of two purified components, designated as hytramycin-V and hytramycin-I, were determined by high-resolution mass spectrometry (ESI-IT-TOF) as C 30 H 51 N 9 O 6 and C 31 H 53 N 9 O 6 , resp. Structure elucidation by 1D/2D NMR revealed both to be cyclohexapeptides with three unusual piperazic acid moieties. The MICs against replicating and especially non-replicating Mtb fall into the range of existing anti-TB drugs, such as streptomycin and capreomycin, and were maintained against Mtb strains that represent the major global clades, as well as H 37 Rv-isogenic strains that are resistant to individual clinical anti-TB drugs.