One new indolocarbazole alkaloid from the <i>Streptomyces</i> sp. A22

<p>One new indolocarbazole alkaloid, 12-N-methyl-k252c, together with eight known indolocarbazoles were isolated from the rice solid fermentation of the marine-derived <i>Streptomyces</i> sp<i>.</i> A22. Their structures were elucidated on the basis of spectroscopic methods (UV, IR, HRESITOF MS, 1D NMR and 2D NMR). All of these compounds were evaluated for bromodomain-containing protein 4 (BRD4) inhibitory activities and cytotoxic activity assay, respectively. Compounds <b>4</b> and <b>5</b> showed moderate cytotoxic activity with an IC<sub>50</sub> value of 3.52 and 3.93 μM, respectively. Additionally, compound <b>1</b> also was tested for enzyme inhibition activities of protein kinases and showed moderate activity with IC<sub>50</sub> values of 0.91–1.84 μM.</p>