Synthesis and synergistic antifungal effects of monoketone derivatives of curcumin against fluconazole-resistant Candida spp.

Twenty-three monoketone derivatives of curcumin were synthesized to investigate the synergy with fluconazole against fluconazole-resistant Candida spp. The minimal inhibitory concentration (MIC80) and the fractional inhibitory concentration index (FICI) of the antifungal synergist fluconazole were measured against fluconazole-resistant C. albicans, C. tropicalis and C. krusei in vitro. Most of these compounds showed good synergistic activities against C. tropicalis. Among them, compound 9 exhibited significant synergistic activities against Candida spp. SARs were also discussed. In particular, a cell growth test exhibited that a combination of 1 μg ml-1 fluconazole and 64 μg ml-1 or 128 μg ml-1 compound 9 showed the most potent fungicidal effect against C. tropicalis. The synergistic effect may be associated with the changes of the intracellular ATP content and cell membrane permeability. Our results provided a basis for future evaluation and development of these compounds as leads for therapeutics for fluconazole-resistant candidiasis.