Discovery of pyridomycin derivatives as InhA inhibitors from actinomycetes through molecular networking and an In-House tandem mass library

A screen of ~ 4000 actinomycetes strains identified Streptomyces sp. W3009 as a producer of the antituberculosis agent pyridomycin. Using a mass spectrometry-based metabolomics approach coupled with molecular networking, we identified seven pyridomycin derivatives, six of which were novel. Three of these novel compounds were linear, featuring a unique 3-hydroxypicolinic acid-L-threonine-3-(3-pyridyl)-L-alanine (3HP-T-3PA) scaffold. Their structures were elucidated via detailed NMR studies. While two cyclic derivatives (4 and 5) showed modest antitubercular activity, the three linear derivatives, despite possessing the key 3HP-T-3PA moiety, exhibited no inhibitory activity. This intensive MS-based approach demonstrates the important role of such techniques in the discovery of novel biologically active core structures and their natural derivatives.