New alkaloids from Taiwanese zoanthid Zoanthus kuroshio

Fractionation of an ethanolic extract from Zoanthus kuroshio has resulted in the isolation of four new alkaloids, kuroshines C-F (1-4), together with three known compounds, kuroshines A and B (5 and 6) and zoanthenamide (7). Kuroshine C (1) may be categorized as a new oxidative derivative of kuroshine A (5) with a ketone group at C-11. All of these marine alkaloids possess a densely functionalized octacyclic ring system on the basis of the zoanthamine framework. The structures of these compounds were elucidated through the interpretation of spectroscopic methods, especially 2D NMR technologies (COSY, HMQC, HMBC, and NOESY). The cytotoxic activities of the isolates against A-549, Hep-G2, and MDA-MB-231 cancer cell lines were evaluated.