Marine sponges are well known as rich sources of biologically natural products. Growing evidence indicates that sponges harbor a wealth of microorganisms in their bodies, which are likely to be the true producers of bioactive secondary metabolites. In order to promote the study of natural product chemistry and explore the relationship between microorganisms and their sponge hosts, in this review, we give a comprehensive overview of the structures, sources, and activities of the 774 new marine natural products from sponge-derived microorganisms described over the last two decades from 1998 to 2017.

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Main observation and conclusion The new racemic and dimeric indole alkaloids with the characteristic cyclopenta[b]indole backbone, (+)‐ and (–)‐spondomine (1a/1b), were isolated from a cultured sponge Tedania anhelans. A semi‐synthesis was employed to obtain 1a/1b and the other four stereoisomers 1c—1f. Their structures were determined by spectroscopic analysis, single‐crystal X‐ray, and quantum chemical calculations. Six stereoisomers differ in bioactivity according to their absolute configurations. Especially, (+)‐spondomine (1a) displayed cytotoxicity against the K562 cell line and exhibited stronger Wnt and HIF1 dual signaling inhibitory activity at 5 μmol/L than the positive control, which offers an exciting starting point for further investigations. All stereoisomers significantly promoted angiogenesis and showed moderate anti‐inflammation in zebrafish. A quantum chemical calculation and deuteration experiment were applied to unveil the reaction mechanism which guides the synthesis of the target compounds.