Oral candidiasis is an infection of the oral cavity commonly caused by Candida albicans. Endodontic treatment failure has also been found to be persistent from C. albicans in the root canal system. Despite the availability of antifungal drugs, the management of Candida oral infection is difficult as it exhibits resistance to a different class of antifungal drugs. Therefore, it is necessary to discover new antifungal compounds to cure fungal infections. This study aimed to examine the antifungal susceptibility of Capsaicin, an active compound of chili pepper. The susceptibility of Capsaicin and Fluconazole was tested against the Candida species by the CLSI (M27-A3) method. The effect of Capsaicin on the fungal cell wall was examined by the ergosterol inhibitory assay and observed by the scanning electron micrograph. The MIC range of Capsaicin against Candida isolates from oral (n = 30), endodontic (n = 8), and ATCC strains (n = 2) was 12.5−50 µg/mL. The MIC range of Fluconazole (128- 4 µg/mL) significantly decreased (2- to 4-fold) after the combination with Capsaicin (MIC/4) (p < 0.05). Capsaicin (at MIC) significantly reduced the mature biofilm of C. albicans by 70 to 89% (p < 0.01). The ergosterol content of the cell wall decreased significantly with the increase in the Capsaicin dose (p < 0.01). Capsaicin showed high sensitivity against the hyphae formation and demonstrated a more than 71% reduction in mature biofilm. A fluorescence microscopy revealed the membrane disruption of Capsaicin-treated C. albicans cells, whereas a micrograph of electron microscopy showed the distorted cells’ shape, ruptured cell walls, and shrinkage of cells after the release of intracellular content. The results conclude that Capsaicin had a potential antifungal activity that inhibits the ergosterol biosynthesis in the cell wall, and therefore, the cells’ structure and integrity were disrupted. More importantly, Capsaicin synergistically enhanced the Fluconazole antifungal activity, and the synergistic effect might be helpful in the prevention of Fluconazole resistance development and reduced drug-dosing.
Keywords: Capsaicin; anticandidal; chili pepper; ergosterol.