Indole-based alkaloids from deep-sea bacterium Shewanella piezotolerans with antitumor activities

Chromatographic separation of a crude extract obtained from a fermentation broth of a chemically unknown bacterium Shewanella piezotolerans WP3 collected in deep-sea yielded three new indole alkaloids namely shewanellines A (1a), B (1b) and C (2), together with 12 known indole alkaloids. The structures were unambiguously elucidated on the basis of 1D and 2D NMR (H-1, C-13, COSY, HMBC, HSQC and NOESY) in association with MS and CD data. Compounds 1-4, 7, 9 and 11-14 were selected for the evaluation of their cytotoxic activities against human tumor cell lines HL-60 and BEL-7402, whereas compounds 2, 4 and 9 exhibited significant inhibition toward HL-60.