ABSTRACT
Analysis of an antimicrobial culture broth extract of the sponge-derived actinomycete Streptomyces sp. (strain G246) led to the isolation of two new lavandulylated flavonoids, 6-lavandulyl-7-methoxy-5,2',4'-trihydroxylflavanone (1) and 5'-lavandulyl-4'-methoxy-2,4,2',6'-tetrahydroxylchalcone (2), along with eight known compounds 3-10. Their structures were established by spectral data analysis, including MS, 1D, 2D-NMR and CD. The absolute configurations of 1 and 2 were suggested by comparison of their experimental and calculated electronic circular dichroism spectra. All the isolated compounds were evaluated for their antimicrobial activity against a panel of clinically significant microorganisms. Compounds 1 and 2 had a broad-spectrum of antimicrobial activity. Additionally, except the strain Escherichia coli, compound 2 exhibited remarkable inhibitory activity against Pseudomonas aeruginosa, Salmonella enterica, Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, and Candida albicans strains.
Subject(s)
Anti-Infective Agents/isolation & purification , Flavonoids/isolation & purification , Porifera/microbiology , Streptomyces/chemistry , Actinomycetales/chemistry , Animals , Anti-Infective Agents/chemistry , Anti-Infective Agents/pharmacology , Bacillus cereus/drug effects , Candida albicans/drug effects , Enterococcus faecalis/drug effects , Escherichia coli/drug effects , Flavonoids/chemistry , Flavonoids/pharmacology , Microbial Sensitivity Tests , Pseudomonas aeruginosa/drug effects , Staphylococcus aureus/drug effectsABSTRACT
Analysis of an antimicrobial extract prepared from culture broth of the marine-derived actinomycete Streptomyces sp. G278 led to the isolation of ten compounds, 1-10. Two compounds, 2,5-Bis(5-tert-butyl-2-benzoxazolyl)thiophene (1), and 3-hydroxyl-2-methylpyridine (2) were isolated from a natural source for the first time. The structures of the isolated compounds were established by their spectral data analysis, including mass spectrometry, 1D-NMR, 2D-NMR, and X-ray crystallographic analysis in case of compound 3. All isolated compounds were evaluated for their antimicrobial activity against a panel of clinically significant microorganisms. Compounds 1 and 3 selectively inhibited Enterococcus faecalis (MIC: 256 µg/mL). Compound 2 was found to have antibacterial and antifungal activity against Escherichia coli (MIC: 64 µg/mL), Salmonella enterica (MIC: 256 µg/mL), Staphylococcus aureus (MIC: 256 µg/mL), Enterococcus faecalis (MIC: 256 µg/mL), and Candida albicans (MIC: 64 µg/mL). Except for compounds 9 and 10, the other known metabolites (4-8) also exhibited antimicrobial activity.
