Basic Study On The Antifungal Activity And Action Mechanism Of Honokiol

Recently, with the indiscriminated use of antifungal agents in clinical therapy, resistance is growing in clinical isolates from patients, the first line antifungal agents can not achieve the treatment effect of fungal infections. Therefore, new antifungal agents and new therapeutic method should be developed to solve this problem. Honokiol (HNK), one active ingredient isolated from the chinese herbal medicine Magnolia officinalis, has the activities of anti-tumor, anti-inflammatory, antibacterial, inhibition of platelet aggregation, etc. HNK has great great scientific value and clinical significance.In this study, the minimum inhibitory concentrations (MICs) of HNK and fluconazole (FLC) against 22 clinical isolates of FLC-resistant Candida albicans (C. albicans) strains, two multidrug efflux gene overexpressed clinical isolates of C. albicans, TW 00313 (CDR1,2 overexpression) and TW 07239 (MDR1? ERG11 overexpression), and 3 quality control strains, C. albicans ATCC 10231, Candida parapsilosis (C. parapsilosis) ATCC 90018, Candida krusei (C. krusei) ATCC 6258 were determined by broth microdilution as described by Clinical and Laboratory Standards Institute (CLSI). Checkerboard method was conducted to evaluate the antifungal effect of combination of HNK and FLC by fractional inhibitory concentration index (FICI). Using time-killing test to confirm the in vitro synergistic activity of HNK and FLC against clinical isolates of FLC-resistant C. albicans. Then, FLC-resistant C. albicans were injected via the lateral tail vein of mice, mice with candidiasis were treated successfully by different drugs. Compare the survival rate and the colony forming unit in infected and treated mice kidney to evaluate the in vivo synergistic activity of HNK and FLC against clinical isolates of FLC-resistant C. albicans.The results shows that HNK has good antifungal activity against C. albicans. When combinated with HNK, MICs of FLC against C. albicans decreased by 64 to 512 fold. HNK and FLC shows better treatment effect in mice with candidiasis, the survival rate reached to 100%, and the colony forming unit in kidney was the lowest one.Laser scan confocal microscope (LSCM) was employed to research the antifungal mechanism of HNK preliminary by observing the form of C. albicans cells and the content of DNA and RNA. In the results, volume of cells and the content of DNA and RNA increased, notably, when C. albicans was treated by HNK. HNK may influence the nucleic acid in fungal and prevent fungal fission.All the experiments demonstrate the synergistic activity of HNK and FLC against clinical isolates of FLC-resistant C. albicans. That provided new therapeutic method for fungus disease and theoretical basis for studying HNK in future.