Screening of flavonoids as candidate antibiotics against Enterococcus faecalis.

beta-Ketoacyl acyl carrier protein synthase (KAS) III, the most divergent member of the condensing enzyme family, is a key catalyst in bacterial fatty acid biosynthesis and, thus, an attractive target for novel antibiotics. Here, we perform docking studies between Enterococcus faecalis KAS III (efKAS III) and one flavanone and 11 hydroxyflavanones with hydroxy groups at various positions. The MIC values of these flavanones for E. faecalis and vancomycin-resistant E. faecalis (VREF) were measured, and binding affinities to efKAS III were determined. Naringenin (9), eriodictyol (10), and taxifolin (12), with high-scoring functions and good binding affinities, docked well with efKAS III, resulting in MIC values in the range 128-512 microg/mL. Our results indicate that hydrogen bonds between the 5- and 4'-hydroxy groups and the side-chain of Arg38 and the backbone carbonyl of Phe308 are the key interactions for efKAS III inhibition. These flavanones are good candidate KAS III inhibitors and may be utilized as effective antimicrobials.