Synthesis and antifungal activity of substituted 2,4,6-pyrimidinetrione carbaldehyde hydrazones

Opportunistic fungal infections caused by the Candida spp. are the most common human fungal infections, often resulting in severe systemic infections-a significant cause of morbidity and mortality in at-risk populations. Azole antifungals remain the mainstay of antifungal treatment for candidiasis, however development of clinical resistance to azoles by Candida spp. limits the drugs' efficacy and highlights the need for discovery of novel therapeutics. Recently, it has been reported that simple hydrazone derivatives have the capability to potentiate antifungal activities in vitro. Similarly, pyrimidinetrione analogs have long been explored by medicinal chemists as potential therapeutics, with more recent focus being on the potential for pyrimidinetrione antimicrobial activity. In this work, we present the synthesis of a class of novel hydrazone-pyrimidinetrione analogs using novel synthetic procedures. In addition, structure-activity relationship studies focusing on fungal growth inhibition were also performed against two clinically significant fungal pathogens. A number of derivatives, including phenylhydrazones of 5-acylpyrimidinetrione exhibited potent growth inhibition at or below 10 mu M with minimal mammalian cell toxicity. In addition, in vitro studies aimed at defining the mechanism of action of the most active analogs provide preliminary evidence that these compound decrease energy production and fungal cell respiration, making this class of analogs promising novel therapies, as they target pathways not targeted by currently available antifungals. (C) 2013 Elsevier Ltd. All rights reserved.