title: Flucytosine analogues obtained through Biginelli reaction as efficient combinative antifungal agents.
abstract: Invasive fungal infection is a problem that continues to challenge the healthcare sector. New antifungals and new therapeutic strategies are needed to address this challenge. We previously reported that the combination of a synthetic compound with a drug with known mechanism of action is a good strategy to treat aggressive and resistant fungi. Here we revisited our approach and synthesized structural analogues of flucytosine, which is a synthetic antifungal and is being studied for its use in combination therapy with other antifungal drugs. Pyrimidin-one and -thione (often known as DHPM's) as flucytosine analogues were obtained through a Biginelli reaction of corresponding aldehydes, ethylacetoacetate and urea/thiourea. Structure was confirmed by FTIR,1HNMR,13CNMR, COSY and MS (ESI+) analysis. All the newly synthesized derivatives were evaluated for the antifungal activity alone and in combination of two most commonly used antifungal drugs, amphotericin B and fluconazole against different clinically isolated Candida albicans strains. Minimum inhibitory concentration results confirmed that BG4 possess high antifungal activity against all the tested strains (MIC = 1-32 μg/ml). For all the combinations with amphotericin B and fluconazole, 37% were synergistic followed by 30% additive and 24% indifferent interactions. Interestingly, 9% antagonistic interaction was observed when BG1 and BG3 were combined with fluconazole, however, no antagonistic interaction was observed with amphotericin B. In-depth studies of all the synergies were done by constructing isobolograms with nine different ratio combinations. These results warrant the use of DHPM derivatives as chemosensitising agents which could lower down the dosages of the antifungal drugs to treat invasive fungal diseases.
authors.affiliation: Departmento de Quimica, FCTUC, Universidade de Coimbra, Rua Larga, 3004-535, Coimbra, Portugal; Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center at Houston, 1881 East Road, Houston, TX 77054, USA. Electronic address: waniyouns@gmail.com.
authors.forename: Mohmmad Younus
authors.initials: MY
authors.lastname: Wani
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, School of Pathology of NHLS and University of the Witwatersrand, Faculty of Health Sciences, 2193 Johannesburg, South Africa.
authors.forename: Aijaz
authors.initials: A
authors.lastname: Ahmad
authors.affiliation: Departmento de Quimica, FCTUC, Universidade de Coimbra, Rua Larga, 3004-535, Coimbra, Portugal.
authors.forename: Santosh
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Departmento de Quimica, FCTUC, Universidade de Coimbra, Rua Larga, 3004-535, Coimbra, Portugal. Electronic address: asobral@ci.uc.pt.
authors.forename: Abilio J F N
authors.initials: AJ
authors.lastname: Sobral
mesh_terms: D000935:Antifungal Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000302:isolation & purification; D002177:Candidiasis / Q000382:microbiology; D004357:Drug Synergism; D005437:Flucytosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D013057:Spectrum Analysis
chemical_list: D000935:Antifungal Agents; D005437:Flucytosine
keywords: Antifungal; Biginelli reaction; Flucytosine analogues; Pyrimidinone; Synergy