In vitro activity of xanthorrhizol against Candida glabrata, C. guilliermondii, and C. parapsilosis biofilms

The formation of Candida biofilms has important clinical ramifications, because these biofilms exhibit increased resistance to conventional antifungal therapies. The aim of this study was to investigate the activity of xanthorrhizol on biofilms produced by non-C. albicans Candida (NCAC) species, including C. glabrata, C. guilliermondii, and C. parapsilosis. NCAC biofilms were generated in flat-bottom 96-well microtiter plates and quantified using the XTT (2, 3 - bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenyl amino) carbonyl]-2H-tetrazolium hydroxide) reduction assay. The NCAC biofilms at adherent, intermediate, and mature growth phases were treated with 0.5-512 μg/ml of xanthorrhizol for 24 h. The ranges of sessile minimum inhibitory concentrations (SMICs) of xanthorrhizol against C. glabrata, C. guilliermondii, and C. parapsilosis biofilms were 8-32 μg/ml, 8-16 μg/ml, and 8-64 μg/ml, respectively. Xanthorrhizol affected cell density that had an indirect effect on the biofilm OD490. The compound eradicated the viable cells of the C. glabrata and C. parapsilosis biofilms at the adherent growth phase at 16 μg/ml and that of C. guilliermondii at 8 μg/ml. Treatment with 128 μg/ml of xanthorrhizol reduced the OD490 of C. glabrata, C. guilliermondii, and C. parapsilosis biofilms at the mature growth phase by 77.8%, 88.5%, and 64.5%, respectively. These results indicate that xanthorrhizol exhibits potent activity against NCAC biofilms in vitro. Therefore, xanthorrhizol has potential therapeutic value in treating biofilm-associated NCAC infections and should be further evaluated in vivo.