Antifungal Activity of Caffeine in Combination with Fluconazole against Candida albicans

Iranian (Lahijan) black tea caffeine has been previously shown to have antifungal activity against Candida albicans. The aim of this study was to investigate whether the combination of caffeine and fluconazole (FLU) has an effective antifungal activity on a FLU-resistant (MIC >64mgL-1) C. albicans PTCC5027.
Caffeine from Lahijan black tea was extracted and its pharmacological effects against 20 clinical isolates of FLU-sensitive and resistant C. albicans was evaluated by Colony Forming Units (CFU) method. Furthermore, the synergistic effect of caffeine and FLU against PTCC-5027strain was investigated.
Our results indicate the antifungal efficacy of Lahijan black tea caffeine on C. albicans isolates and subsequent identification of caffeine in combination with FLU againstPTCC-5027 strain. The concentrations of caffeine causing 90% growth inhibition (MIC90) for PTCC-5027 strain, FLU-resistant and -sensitive C. albicans isolates were 25mgL-1, 24.4mgL-1 and 37.2mgL-1,respectively. The combination of caffeine with FLU showed stronger antifungal activity against C. albicans PTCC5027. The addition of 12.5mgL-1 caffeine to FLU 10-50 mgL-1 (below MIC90) inhibited the growth of C. albicans PTCC5027 by 99.3%–99.7%, the concentrations at which neither caffeine nor FLU alone affected the growth.
It can be concluded that caffeine has antifungal effect on C. albicans and in combination with FLU can enhance the antifungal activity of FLU against C. albicans. The synergism of the combination of caffeine and FLU induces multiple antifungal effects, resulting in the use of lower doses of the FLU. It suggests that this can decrease the side effects of antifungal drugs.