Genomic analyses lead to novel secondary metabolites

Genomic analyses of Amycolatopsis orientalis ATCC 43491 strain, deposited as a vancomycin producer, revealed the presence of genetic loci for the production of at least 10 secondary metabolites other than vancomycin. One of these gene clusters, which contained a type I polyketide synthase, was predicted to direct the synthesis of novel class of compound, a glycosidic polyketide ECO-0501 (1). Screening of culture extracts for a compound with the predicted physicochemical properties of the product from this locus, led to the isolation of the 13-O-glucuronide of 13-hydroxy-2,12,14,16,22-pentamethyl-28(N-methyl-guanidino)-octacosa-2,4,6,8,10,14,20,24-octaenoic acid (2-hydroxy-5-oxo-cyclopent-1-enyl)-amide (ECO-0501, 1). The structure, confirmed by spectral analyses including MS, and ID and 2D NMR experiments, were in accord with that predicted by genomic analyses. ECO-0501 possessed strong antibacterial activity against a series of Gram-positive pathogens including several strains of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE). ECO-0501 was chemically modified by esterification (1a similar to 1c), N-acetylation (1d) and hydrogenation (le) in order to explore structure activity relationships (SAR).