Antimicrobial lavandulylated flavonoids from a sponge-derived actinomycete.

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.