New linear bromopyrrole-imidazolidine alkaloids from the Formosan sponge <i>Agelas nakamurai</i>

Chemical investigation of the natural products from Formosan sponge <i>Agelas nakamurai</i> led to the isolation of two undescribed bromopyrrole-imidazolidine alkaloids, nakamudines A and B. The structures of the compounds were determined by extensive spectroscopic analyses, including 2D NMR correlations, while their relative configurations were resolved <i>via</i> NOESY correlation analysis. The alkaloids were assigned as rare linear bromopyrrole alkaloidal epimers possessing an 2,4-imidazolidinedione (hydantoin) moiety. The cytotoxicity and antibacterial activity of these alkaloids were assessed, however, they did not exhibit significant activity in the bioassays conducted.