Abstract: Candida  spp. cause various infections involving the skin, mucosa, deep tissues, and even life-threatening candidemia. They are regarded as an important pathogen of nosocomial bloodstream infection, with a high mortality rate. As a result of prolonged exposure to azoles, the therapeutic failure associated with azoles resistance has become a serious challenge in clinical situations. Therefore, novel, alternative antifungals are required urgently. In the present study, the CLSI M-27A broth microdilution method and the 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay were used to evaluate the antifungal effects of magnolol against various standard Candida  strains in planktonic mode and biofilm formation, respectively. The antifungal activity of magnolol was demonstrated in planktonic C. albicans  and non-albicans Candida  species, especially fluconazole-resistant Candida krusei , with the minimum inhibitory concentrations ranging from 10 to 40 µg/mL. The BMIC₉₀ (minimum concentration with 90% Candida  biofilm inhibited) values of magnolol ranged from 20 to 160 µg/mL, whereas the BMIC₉₀ values of fluconazole were more than 128 µg/mL. As an alternative and broad-spectrum antifungal agent, magnolol might be of benefit to the treatment of refractory Candida  infection.
Keywords: magnolol, inhibition, Candida  spp., biofilm