Influence of menthol on biofilm formation, ergosterol content, and cell surface hydrophobicity of Candida glabrata.

Resistance to synthetic antifungals has become one of the leading public health challenges around the world. Accordingly, novel antifungal products like naturally occurring molecules can be one of the potential ways to reach efficient curative approaches to control candidiasis. This work evaluated the effect of menthol on cell surface hydrophobicity (CSH), biofilm formation, growth, and ergosterol content of Candida glabrata, a yeast with a high resistance against antifungal agents. Disc diffusion method (susceptibility to synthetic antifungals), broth micro-dilution method (Susceptibility to menthol), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide reduction assay (biofilm formation), High-performance liquid chromatography (HPLC) technique (ergosterol content), and adherence to n-hexadecane (CSH) were employed to determine the influence of menthol against C. glabrata isolates. The minimum inhibitory concentration (MIC) range of menthol versus C. glabrata was 1250-5000 µg/mL (mean ± SD: 3375 ± 1375 µg/mL). The mean rate of C. glabrata biofilm formation was decreased up to 97.67%, 81.15%, 71.21%, 63.72%, 47.53%, 26.31%, and 0.051% at 625, 1250, 2500, 5000, 10 000, 20 000, and 40 000 µg/mL concentrations, respectively. The percentages of CSH were significant in groups treated with MIC/2 (17.51 ± 5.52%) and MIC/4 (26 ± 5.87%) concentrations of menthol. Also, the percentage changes in membrane ergosterol were 15.97%, 45.34%, and 73.40% at 0.125, 0.25, and 0.5 mg/mL concentrations of menthol, respectively, in comparison with untreated control. The results showed the menthol impact versus sessile and planktonic C. glabrata cells, and the interference with ergosterol content, CSH, and biofilm formation, which made it a potent natural antifungal.