Original article Synthesis, cytotoxicity and apoptosis of cyclotriphosphazene compounds as anti-cancer agents Tuba Yıldırım a, * , Kemal Bilgin b , Gönül Yenilmez Çiftçi c , Esra Tanrıverdi Eçik c , Elif S ¸ enkuytu c , Yıldız Uluda  g d , Leman Tomak e , Adem Kılıç c a Department of Biology, Faculty of Art and Science, Amasya University, 05100 Amasya, Turkey b Department of Medical Microbiology, Faculty of Medicine, Ondokuz Mayıs University, 55139 Samsun, Turkey c Department of Chemistry, Gebze Institute of Technology, 41400 Gebze/Kocaeli, Turkey d UEKAE e The Scientific and Technological Research Council of Turkey (TUBITAK), 41470 Gebze/Kocaeli, Turkey e Department of Biostatistic, Faculty of Medicine, Ondokuz Mayıs University, 55139 Samsun, Turkey article info Article history: Received 23 September 2011 Received in revised form 7 March 2012 Accepted 9 March 2012 Available online 19 March 2012 Keywords: Cyclotriphosphazene Spermine derivatives Biological activity Cytotoxic activity Apoptosis abstract In the present study, a number of new dispirobino and dispiroansa spermine derivatives of cyclo- triphosphazene (8e10, 13) were synthesized and characterized by elemental analysis, mass spectrom- etry, 1 H and 31 P NMR spectroscopy. At first, in vitro cytotoxic activity of cyclotriphosphazene compounds (1e14) against HT-29 (human colon adenocarcinoma), Hep2 (Human epidermoid larynx carcinoma), and Vero (African green monkey kidney) cell lines was investigated. Our study showed that most of these compounds stimulate apoptosis and they have cytotoxic effects for HT-29 and Hep2 cells. Additionally, these compounds (1e14) were investigated for their antibacterial activity against gram-positive (Staphylococcus aureus), gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria and for their antifungal activity against Candida albicans, and were shown to be inactive. Ó 2012 Elsevier Masson SAS. All rights reserved. 1. Introduction Cancer is a leading cause of death worldwide and accounted for 7.6 million deaths (around 13% of all deaths) in 2008 [1]. Treatment options for a cancer patient vary depending on the type of cancer, its location and the stage at which it is diagnosed. The adminis- tration of anti-cancer drugs is one of the effective cancer treatment options, and search for new anti-cancer agents is a great task as not only many cancer types exist but also the response of each indi- vidual to different anti-cancer drugs may vary considerably. Another challenge is to design chemicals that have minimum adverse effects on normal cells. Many compounds with different structures have been tested by researchers in the search for anti-cancer drugs. Although a number of compounds exhibit therapeutical properties and are currently used for treatment, the search for new drugs with improved efficiency and minimum side effects still continues. Cyclo- triphosphazene derivatives have attracted the attention of researchers to be used as potential anti-cancer agents. Interest in cyclotriphosphazenes as anti-cancer agents, previously mentioned by Labarre et al. [2], has been enhanced by the finding of aziridino- and polyamine-linked cyclotriphosphazenes which are active on a large series of tumour cells [3,4]. A number of studies have been devoted to describe the antitumour activity of cyclo- triphosphazenes [5e8]. Cyclotriphosphazenes, having a variety of applications in science and technology, are an important class of inorganic ring system [9]. Chemical and physical properties of cyclotriphosphazenes change with the substituted side groups. So, it is possible to design materials with special properties such as anti-cancer agents [5e7], liquid crystals [10,11], electrical conduc- tivity [12], hydraulic fluids and lubricants [13,14], flame retardant properties [15], elastomers [16], rechargeable batteries [17] and biomedical materials [18,19]. In addition, biological activities of cyclotriphosphazene derivatives against various bacterial and fungal species are known [20,21]. The native polyamines are essential growth factors for cells and polyamine derivatives have been shown to have cytotoxic activity against numerous human cancer cell lines (e.g., breast, prostate, etc) [22e24]. Polyamine-based small molecules have been devel- oped for use as biochemical probes and as potential therapies for a variety of diseases [25]. The polyamines inhibit cell growth and * Corresponding author. Tel.: þ90 358 2421613; fax: þ90 358 2421616. E-mail address: yildirimt55@gmail.com (T. Yıldırım). 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 2012 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ejmech.2012.03.018 European Journal of Medicinal Chemistry 52 (2012) 213e220