Bulbimidazoles A-C, Antimicrobial and Cytotoxic Alkanoyl Imidazoles from a Marine Gammaproteobacterium Species.

Three new alkanoyl imidazoles, designated bulbimidazoles A-C (-), were found from the culture extract of the gammaproteobacterium sp. DC3-6 isolated from a stony coral of the genus . The absolute configuration of the -methyl substitution in was established to be a mixture of ()- and ()-configurations in a ratio of 9:91 by applying the Ohrui-Akasaka method. Compounds - displayed unique broad-spectrum antimicrobial activity against Gram-positive and -negative bacteria and fungi with MICs ranging from 0.78 to 12.5 μg/mL. They also exhibited cytotoxicity toward P388 murine leukemia cells with IC in the micromolar range.