Inhibitory Effects of Nitrogenous Metabolites from a Marine-Derived Streptomyces bacillaris on Isocitrate Lyase of Candida albicans .

Two nitrogenous metabolites, bacillimide ( 1 ) and bacillapyrrole ( 2 ), were isolated from the culture broth of the marine-derived actinomycete Streptomyces bacillaris . Based on the results of combined spectroscopic and chemical analyses, the structure of bacillimide ( 1 ) was determined to be a new cyclopenta[ c ]pyrrole-1,3-dione bearing a methylsulfide group, while the previously reported bacillapyrrole ( 2 ) was fully characterized for the first time as a pyrrole-carboxamide bearing an alkyl sulfoxide side chain. Bacillimide ( 1 ) and bacillapyrrole ( 2 ) exerted moderate (IC 50 = 44.24 μM) and weak (IC 50 = 190.45 μM) inhibitory effects on Candida albicans isocitrate lyase, respectively. Based on the growth phenotype using icl -deletion mutants and icl expression analyses, we determined that bacillimide ( 1 ) inhibits the transcriptional level of icl in C. albicans under C 2 -carbon-utilizing conditions.