Alizarin and Chrysazin Inhibit Biofilm and Hyphal Formation by Candida albicans

Abstract

Candida albicans is one of the most common pathogen causes fungal infections. This opportunistic pathogen can form biofilms comprised of yeast, hyphae and pseudo hyphal elements, and the hyphal form C. albicans considered as probable virulence factor. We investigated the antibiofilm activities of 13 quinones and anthraquinones related compounds against C. albicans biofilms by using crystal violet and 2,3-bis (2-Methoxy-4-Nitro-5-Sulfo-phenyl)-2H-Tetrazolium-5-Carboxanilide (XTT) reduction assays to assess inhibitions of biofilm growth. Morphological changes in biofilms and biofilm thicknesses were determined by scanning electron microscopy and confocal laser scanning microscopy, respectively. It was found alizarin (1,2-dihydroxyanthraquinone) and chrysazin (1,8-dihydroxyanthraquinone) suppressed C. albicans biofilm formation. Interestingly, alizarin and chrysazin at only 2 μg/ml effectively inhibited hyphal formation and prolonged the survival of C. albicans infected Caenorhabditis elegans, thus showing a distinct antivirulent potential. A structural activity relationship study of alizarin and 6 other anthraquinones showed the presence of a hydroxyl group at C-1 position which is important for antibiofilm and antifilamentation activities. Transcriptomic analyses revealed that alizarin downregulated the expression of several hypha-specific and biofilm related genes (ALS3, ECE1, ECE2, and RBT1). Furthermore, unlike the commercial antifungal drug fluconazole, no acute toxic effect was observed when uninfected nematodes were exposed to alizarin at concentrations up to 1 mg/ml. The results of this study indicate alizarin suppresses the virulence of C. albicans in vivo which suggests alizarin may be considered as a potential candidate for further investigations to develop antifungal agent against fungal pathogen in vivo.

Efficacy of 7‐benzyloxyindole and other halogenated indoles to inhibit Candida albicans biofilm and hyphal formation

“…Initially, we investigate whether indole derivatives affect biofilm formation by fluconazole‐resistant C. albicans DAY185 (Manoharan et al ., 2017a,b), and cell growth was simultaneously measured in the presence of indole derivatives. Of the 34 commercially available indole derivatives examined, 7‐benzyloxyindole, 4‐fluoroindole and 5‐iodoindole significantly reduced biofilm formation at concentrations of 0.1 and 0.5 mM (Table S1).…”

“…As previously reported, DAY185 is resistant to the commercial antifungal fluconazole (MIC ~ 512 μg ml −1 ) (Manoharan et al ., 2017a,b). A single colony was inoculated into 25 ml of PDB and incubated for overnight at 37°C.…”

“…Caenorhabditis elegans strain N2 Bristol CF512 fer‐15 (b26) ; fem‐1 (hc17) (Manoharan et al ., 2017a,b) was used to perform C. albicans virulence assay using the protocol described by (Manoharan et al ., 2017a,b). Briefly, synchronized adults worms were fed on C. albicans lawns for 4 h at 25°C and collected after washing three times with M9 buffer.…”

Reaction-based indicator displacement assay (RIA) for the development of a triggered release system capable of biofilm inhibition

“…Recent efforts by Lee and co-workers have demonstrated that alizarin (10 mg mL À1 ) is an effective inhibitor of biofilm formation for three Staphylococcus aureus (S. aureus) strains and one Staphylococcus epidermidis strain. 20,21 Biofilms are complex bacterial communities that can facilitate antibiotic resistance and impair wound healing. 22 Hence, the development of new systems that can effectively treat or inhibit biofilm formation are highly desirable.…”

“…[23][24][25] ARS was able to inhibit biofilm formation for S. aureus MRSA252 and S. aureus H560 at 100 mM when added during the lag phase of growth (0 h), similar to other reports in the literature for Alizarin. 21 However, ARS was unsuccessful in the inhibition of P. aeruginosa PAO1 and E. coli NCTC 10418 biofilms at concentrations below 100 mM (see Fig. S14-S16, ESI †).…”