No abstract

In the course of optimizing pargamicin A production in Amycolatopsis sp. ML1-hF4, we discovered novel cyclic depsipeptide compounds in the broth and designated them valgamicins A, C, T and V. The structures of these molecules were determined by spectroscopic studies, advanced Marfey's method and X-ray crystal structural analysis. Valgamicin C contains the extremely rare amino acid cleonine. To our knowledge, this is the first report of a cleonine-containing metabolite from a naturally isolated microorganism without any breeding or mutation treatment. None of the valgamicins showed potent antibacterial activity against either Gram-positive or -negative bacteria. Valgamicins A, C and T exhibited moderate cytotoxicity against human tumor cell lines.The Journal of Antibiotics advance online publication, 15 November 2017; doi:10.1038/ja.2017.135.