J. Indian Chern. Soc., Vol. 90, June 2013, pp. 771-776 Cytotoxic properties of two families of benzaldehyde thiosemicarbazone complexes of palladium Sarmistha Haldera, Piyali Paula, Rama Acharyyaa, Falguni Basulia, Asama Mukherjeeb, Utpal Sanyalb and Samaresh Bhattacharyaa* aDepartment of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata-700 032, India : samaresh _b@hotmal.J. com bDepartment of Anticancer Drug Development, Chittaranjan National Cancer Institute, Kolkata-700 026, India Manuscript received online 16 July 2012. accepJed 20 July 2012 Abstract : Reaction of thiosernicarbazones (HL-R, where H stands for the dissociable hydrazinic pro- ton- and R (R = OCH 3 , CH 3 , H, Cl and N0 2 ) for the substituent) with trans-[Pd(PPh 3 ) 2 CI 2 ] and Na 2 [PdCI 4 ] afford complexes of type [Pd(PPh 3 )(L-R)CI] and [Pd(L-R) 2 ] respectively. In vitro cytotoxicity screenings of these complexes along with four human clinical drugs, viz. cisplatin, BCNU, 5-fluorouracil (5-FU) and hydtoxyurea, have been carried out in two human tumor cell lines, viz. pro myelocytic leukemia HL-60 and histiocytic lymphoma U-937. Majority of these complexes show remarkably low IC50 value and are found to be much more cytotoxic than the reference anticancer drugs in both the cell lines. Apoptosis study in HL-60 with two selected complexes from each group shows that at 5 and 10 JLM concentration they induce apoptosis to a greater extent than cisplatin and camptothecin. Keywords : Benzaldehyde thiosemicarbazones, palladium complexes, cytotoxic properties. Introduction The chemistry of thiosemicarbazone complexes of the transition metal ions has been receiving significant cur- rent attention, primarily because of the bioinorganic re- levance of these complexes 1 . A large majority of the thiosemicarbazone complexes have found wide medicinal applications owing to their potentially beneficial biologi- cal (viz. antibacterial, antimalarial, antiviral and antitu- mor) Systematic studies on the binding of thiosemicarbazones of selected types to different transi- · tion metal ions are of cbnsiderable importance in this respect. However, we have been exploring the chemistry of platinum metal complexes of the thiosemicarbazones3, mainly because of the variable binding mode displayed by these ligands in their complexes and also to under- stand the driving force behind the observed modes of binding. In a recent publication we have described the synthesis and characterization of two families of palla- dium complexes derived from five 4-R-benzaldehyde thiosemicarbazones (HL-R, where H .stands for the dissociable hydrazinic proton and R for the substituent), as well as their application as catalysts in C-C cross- HL-R coupling reactions3m. We have observed earlier that pal- ladium complexes of thiosemicarbazone ligands exhibit remarkable cytotoxic properties towards different cancer cell lines3i, which have encouraged us to explore such . properties in the palladium complexes of the selected 4- R-benzaldehyde thiosemicarbazones. It may be relevant to mention here that biological properties of palladium complexes of several thiosemicarbazone ligands have been studied well 4 . In the present study, which has emerged out of this exploration, we have selected two "human cell lines, viz. promyelocytic HL-60 and lymphoma U-937, for assessing the cytotoxicity of the palladium complexes, and the observed results are reported herein. 771