Streptocarbazoles A and B, two novel indolocarbazoles from the marine-derived actinomycete strain Streptomyces sp. FMA.

Streptocarbazoles A (1) and B (2), two novel indolocarbazoles featuring unprecedented cyclic N-glycosidic linkages between 1,3-carbon atoms of the glycosyl moiety and two indole nitrogen atoms of the indolocarbazole core, were isolated from the marine-derived actinomycetes strain Streptomyces sp. FMA. Their structures were established by spectroscopic methods, CD spectra, and ECD quantum mechanical calculations. Compound 1 was cytotoxic on HL-60 and A-549 cell lines and could arrest the cell cycle of Hela cells at the G(2)/M phase.