Nonocarbolines A–E, β-Carboline Antibiotics Produced by the Rare Actinobacterium Nonomuraea sp. from Indonesia

Abstract

During the course of our ongoing screening for novel biologically active secondary metabolites, the rare Actinobacterium, <i>Nonomuraea</i> sp. 1808210CR was found to produce five unprecedented <i>β</i>-carboline derivatives, nonocarbolines A-E (<b>1-5</b>). Their structures were elucidated from high-resolution mass spectrometry, 1D and 2D nuclear magnetic resonance spectroscopy, and the absolute configuration of <b>4</b> was determined by using the modified Mosher method. Nonocarboline B (<b>2</b>) displayed moderate antifungal activity against <i>Mucor hiemalis</i>, while nonocarboline D (<b>4</b>) exhibited significant cytotoxic activity against the human lung carcinoma cell line A-549 with the IC₅₀ value of 1.7 µM.