Antifungal Activity of the Plant Molecule Capsaicin Against Oral Candida

Objectives: To examine the antifungal potential of the plant molecule Capsaicin alone and in combination with Fluconazole against clinical oral isolates and ATCC strains of Candida spp.
Methods: After determing the MIC₉₀ of Capsaicin as per NCCLS methods, the synergistic effect of Capsaicin and Fluconazole in terms of MICs was evaluated by checkerboard method. The combined effect of both Capsaicin and Fluconazole was also assessed by growth curve assays. Ultrastructure of treated candida cells was examined by electron microscopy.

Results: MIC₉₀ of Capsaicin against Candida ATCC strains (n=2) and oral isolates (n=30) ranged from 12.5-50 µg/mL. However, MIC₉₀ of Fluconazole ranged from 4-128 µg/mL. The combination of Capsaicin with Fluconazole exhibited a synergistic action against 16 isolates (ΣFICI, ≤ 0.05), and no such effect against 14 isolates (ΣFICI, 0.625-1.0). The results suggested that there was no antagonistic effect of the combination. In combination with Capsaicin, the MIC₉₀ of Fluconazole declined to 2-16 µg/mL. Combination of Capsaicin with Fluconazole drugs showed a high antifungal activity against the tested isolates in growth curve assays. Scanning electron micrograph revealed damage of cell wall and plasma membrane, change of cell shape, and formation of deep furrows and wrinkles on the cell surface. Further, transmission electron micrographs of treated cells showed disintegration of cell walls and rupturing of the plasma membrane.

Conclusions: Capsaicin enhanced the fungicidal effect of Fluconazole that might be helpful in addressing drug-resistant candida infections, in lowering drug dosage, and in minimizing adverse effects of antifungal drugs. The mechanism of action of Capsaicin seems to be through damage of cell membrane and cell wall.