Original article Synthesis and anticandidal activity of new triazolothiadiazine derivatives Mehlika Dilek Altıntop a , Zafer Asım Kaplancıklı a, * , Gülhan Turan-Zitouni a , Ahmet Özdemir a , Gökalp _ Is ¸ can b , Güls ¸ en Akalın c ,S ¸ afak Ulusoylar Yıldırım d a Anadolu University, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 26470 Eskis ¸ ehir, Turkey b Anadolu University, Faculty of Pharmacy, Department of Pharmacognosy, 26470 Eskis ¸ ehir, Turkey c Anadolu University, Faculty of Pharmacy, Department of Biochemistry, 26470 Eskis ¸ ehir, Turkey d Anadolu University, Faculty of Pharmacy, Department of Pharmacology, 26470 Eskis ¸ ehir, Turkey article info Article history: Received 5 July 2011 Received in revised form 9 August 2011 Accepted 15 September 2011 Available online 22 September 2011 Keywords: Triazole Triazolothiadiazine Anticandidal activity Cytotoxicity abstract New triazolothiadiazine derivatives were synthesized via the ring closure reaction of 4-amino-5- substituted-2,4-dihydro-3H-1,2,4-triazol-3-thiones with phenacyl bromides. The compounds were tested in vitro against various Candida species and compared with ketoconazole. Among these compounds, the compound bearing cyclohexyl moiety and p-chlorophenyl substituent on tri- azolothiadiazine ring (2i) was found to be the most potent derivative against Candida albicans (ATCC 90028). It is clear that there is a positive correlation between anticandidal activity and two functional moieties, namely cycloaliphatic group and p-chlorophenyl substituent on triazolothiadiazine ring. The compounds were also investigated for their cytotoxic effects using MTT assay. Compound 2a exhibited the highest cytotoxic activity, whereas compound 2f possessed the lowest cytotoxic activity against NIH/ 3T3 cells. Ó 2011 Elsevier Masson SAS. All rights reserved. 1. Introduction Candida species have emerged as the most common cause of systemic fungal infections worldwide over the last two decades. A large number of studies have attempted to assess risk factors for candidaemia. The most frequently implicated risk factors include treatment with broad-spectrum antibiotics, use of central venous catheters and implantable prosthetic devices, parenteral nutrition, prolonged intensive care unit stay, hemodialysis and immunosup- pression (including HIV infection, neutropenia, use of glucocorti- costeroids, chemotherapeutic agents, and immunomodulators) [1e 7]. Azoles, especially triazole antifungal agents, play a leading role in the treatment of systemic fungal infections owing to their broad spectrum and improved safety profile. The prominent drugs bearing triazole ring are fluconazole, itraconazole, voriconazole, and posaconazole, all of which are widely used antifungal drugs for the treatment of systemic fungal infections [8,9]. The widespread use of these agents has led to the development of resistance in recent years. Several researchers have extensively studied the mechanisms of resistance to azoles in Candida species. At the molecular level, Candida species can develop resistance to azoles via decreased accumulation of the drug resulting from enhanced efflux, interference of their action on lanosterol 14a- demethylase, alterations in other enzymes of the biosynthetic pathway of ergosterol, and decreased permeability of the fungal membrane to the drug. As a consequence of this situation, medic- inal chemists have focused on the development of new effective anticandidal agents [3]. Among triazole derivatives, 1,2,4-triazoline-3-thiones and their fused heterocyclic derivatives including triazolothiadiazines have received considerable attention due to their biological importance [10e12]. Some studies have confirmed that triazolothiadiazine derivatives possess anticandidal activity [13e17]. In continuation of our previous work on the synthesis and antimicrobial evaluation of triazolothiadiazine derivatives [15], herein we described the discovery of new triazolothiadiazine derivatives, which were tested in vitro against various Candida species and investigated for their cytotoxic effects. 2. Chemistry The compounds possessing triazoline-3-thione structure (1aeb) were previously synthesized via the one-pot reaction of thiocarbohydrazide with appropriate propionic acids under solvent-free conditions [18]. New triazolothiadiazine derivatives (2aej) were obtained by the ring closure reaction of 1,2,4-triazoline-3-thiones (1aeb) with * Corresponding author. Tel.: þ90 222 3350580/3776; fax: þ90 222 3350750. E-mail address: zakaplan@anadolu.edu.tr (Z.A. Kaplancıklı). Contents lists available at SciVerse ScienceDirect European Journal of Medicinal Chemistry journal homepage: http://www.elsevier.com/locate/ejmech 0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ejmech.2011.09.020 European Journal of Medicinal Chemistry 46 (2011) 5562e5566