New Glycosylated Secondary Metabolites from Marine-Derived Bacteria

Three new glycosylated secondary metabolites, including a new indole alkaloid, pityriacitrin D (1), and two new trehalose lipids (2 and 3), together with three known compounds (4–6) were isolated from two marine-derived bacterial strains, Bacillus siamensis 168CLC-66.1 and Tsukamurella pseudospumae IV19-045. The structures of 1–3 were determined by extensive analysis and comparison of their spectroscopic data with literature values. The absolute configurations of sugar moieties were determined by chemical derivatization followed by LC-MS analysis. Cytotoxicity of 1–3 against six cancer cell lines was evaluated by SRB assay, and 1 showed moderate activity against all the tested cell lines with GI(50) values ranging from 8.0 to 10.9 µM.