Four new minor brominated indole related alkaloids with antibacterial activities from Laurencia similis.

Four new minor brominated indole related alkaloids (one indoles, 1 , one 1,3-dihydro-indole-2-one, 2 , one carbazole, 3 , and one 2-carbonylamino-benzoate, 4 ) were isolated and identified from Laurencia similis by extensive chromatographic and spectrometric methods. Among them, 1 and 2 were the first example of naturally occurring indole with 3-benzyl group and 1,3-dihydro-indole-2-one with 2-isopropylidene group, respectively, whereas 3 and 4 were the first carbazole alkaloids and 2-carbonylamino-benzoate, respectively, isolated from the genus Laurencia. Moreover, 1 showed the most potent antibacterial activity against seven bacterial strains with MIC values ranging from 2 to 8 μg/mL. [ABSTRACT FROM AUTHOR]