Actinopolymorphols E and F, pyrazine alkaloids from a marine sediment-derived bacterium Streptomyces sp

HPLC-UV-guided fractionation of crude extract from the marine sediment-derived bacterium Streptomyces sp. CNP-944 has yielded two new pyrazine alkaloids, actinopolymorphols E and F (1 and 2), in addition to the previously reported biosynthetic product, actinopolymorphol G (3), and the known actinopolymorphol D (4). The chemical structures of 1-3 were determined based on the interpretation of the 1D, 2D NMR, and MS spectroscopic data. Compound 2 displayed weak antibacterial activities against Kocuria rhizophila, Bacillus subtilis, and Staphylococcus aureus with minimum inhibitory concentration (MIC) values of 16, 64, and 64 μg ml-1, respectively.