The synergistic antibacterial activity of 1-acetyl-beta-carboline and beta-lactams against methicillin-resistant Staphylococcus aureus (MRSA).

1-Acetyl-beta-carboline was isolated as an anti-MRSA agent from the fermentation broth of a marine actinomycete isolated from marine sediment. The producing strain was identified to be Streptomyces sp. by phylogenetic analysis of the 16S rRNA gene sequence. The anti-MRSA agent was isolated by bioactivity-guided fractionation of the culture extract by solvent partitioning, ODS open flash chromatography, and purification with a reversed-phase HPLC. Its structure was elucidated by extensive 2D NMR and mass spectral analyses. Combination of 1-acetyl-beta- carboline with ampicillin exhibited synergistic antibacterial activity against MRSA.