Objectives: The susceptibility of Candida albicans to catechin under varying pH conditions and the synergism of the combination of catechin and antimycotics were evaluated.
Method: Antifungal activity was determined by broth dilution and calculation of cfu.
Results: The antifungal activity of catechin was pH dependent. The concentration of epigallocatechin gallate (EGCg) causing 90% growth inhibition of tested strains of C. albicans was 2000 mg/L at pH 6.0, 500-1000 mg/L at pH 6.5 and 15.6-250 mg/L at pH 7.0. Among catechins, pyrogallol catechin showed stronger antifungal activity against C. albicans than catechol catechin. The addition of 6.25-25 or 3.12-12.5 mg/L EGCg to amphotericin B 0.125 or 0.25 mg/L (below MIC) at pH 7.0 resulted in enhancement, respectively, of the antifungal effect of amphotericin B against amphotericin B-susceptible or -resistant C. albicans. Combined treatment with 3.12-12.5 mg/L EGCg plus amphotericin B 0.5 mg/L (below MIC) markedly decreased the growth of amphotericin B-resistant C. albicans. When fluconazole-susceptible C. albicans was treated with 25-50 mg/L EGCg and fluconazole 0.125-0.25 mg/L (below MIC), its growth was inhibited by 93.0%-99.4% compared with its growth in the presence of fluconazole alone. The combined use of 12.5 mg/L EGCg and fluconazole 10-50 mg/L (below MIC) inhibited the growth of fluconazole-resistant C. albicans by 98.5%-99.7%.
Conclusions: These results indicate that EGCg enhances the antifungal effect of amphotericin B or fluconazole against antimycotic-susceptible and -resistant C. albicans. Combined treatment with catechin allows the use of lower doses of antimycotics and induces multiple antifungal effects. It is hoped that this may help to avoid the side effects of antimycotics.