Identification of novel endophenaside antibiotics produced by Kitasatospora sp. MBT66

Actinomycetes are a major source of bioactive secondary metabolites and are a focal point in the search for novel antimicrobial compounds that are needed to combat multidrug-resistant pathogens. Here, we report the discovery of several novel phenazine-type antibiotics produced by Kitasatospora sp. MBT66. These include the novel glycosylated endophenazines A-E (1-5), together with N-prenylated endophenazine F1 (6). Compounds 1 and 3 contain a 2'-O-methylation of the sugar moiety, which is rare in nature and reported for the first time in connection with phenazines. The structures of the new compounds were determined on the basis of their spectral data, including 1D and 2D NMR, HR-MS and the gene cluster responsible for the biosynthesis of phenazines was identified. All phenazine derivatives showed antimicrobial activity against the Gram-positive Bacillus subtilis, while compounds 1-3 and 5 also inhibited growth of the Gram-negative Escherichia coli.