Flavanones with Potent Antibacterial Activity against Methicillin-resistant Staphylococcus aureus


Department of Dental Pharmacology, Asahi University School of Dentistry, 1851 Hozumi, Hozumi-cho, Motosu-gun, Gifu 501-02, Japan.


Abstract— With the therapeutic concept of using the defensive ability of plants against microbial infections, phytoalexin, an antimicrobial phytochemical was studied for its ability to inhibit the growth of methicillin-resistant Staphylococcus aureus (MRSA). Extracts from Sophora exigua (Leguminosae) were fractionated by serial chromatography and the anti-MRSA activity of each fraction was determined by the agar-plate method. Among the active isolates, 5,7,2′,6′-tetrahydroxy-6-isoprenyl-8-lavandulyl-4′-methoxyflavanone (exiguaflavanone D) completely inhibited the growth of all the MRSA strains examined at the concentration of 1·56–6·25 μg mL−1, and 5, 2′,6′-trihydroxy-8-lavandulyl-7-methoxy-flavanone (exiguaflavanone B) inhibited at a concentration of 50 μg mL−1. This former compound is expected to be a phytotherapeutic agent for MRSA infections as an alternative to conventional antibiotics with unwanted side-effects or the appearance of antibiotic-resistant bacteria.