Spectrochimica Acta Part A 66 (2007) 1171–1174 Synthesis, spectroscopic characterization and biological analysis of a new palladium(II) complex with methionine sulfoxide Pedro P. Corbi a,∗ , Fl´ avia Cagnin a , Lilian P.B. Sabeh b , Antonio C. Massabni a , Claudio M. Costa-Neto b a Departamento de Qu´ ımica Geral e Inorgˆ anica, Instituto de Qu´ ımica, UNESP, Rua Prof. Francisco Degni s/n, CP 355, CEP 14801-970 Araraquara, SP, Brazil b Departamento de Bioqu´ ımica e Imunologia, Faculdade de Medicina de Ribeir˜ ao Preto, USP, 14049-900 Ribeir˜ ao Preto, SP, Brazil Received 10 February 2006; received in revised form 9 June 2006; accepted 9 June 2006 Abstract A new palladium(II) complex with methionine sulfoxide was synthesized and characterized by a set of chemical and spectroscopic techniques. Elemental and mass spectrometry analyses of the solid complex fit to the composition [Pd(C 5 H 10 NO 3 S) 2 ]·H 2 O. 13 C NMR, [ 1 H– 15 N] NMR and infrared spectra indicate coordination of the amino acid to Pd(II) through the carboxylate and amino groups in a square planar geometry. The complex is soluble in water. Biological activity was evaluated by cytotoxic analysis using HeLa cells. Determination of cell death was assessed using a tetrazolium salt colorimetric assay, which reflects the cells viability. After incubation for 48 h, 20% of cell death was achieved at a concentration of 200 mol L -1 of the complex. © 2006 Elsevier B.V. All rights reserved. Keywords: Palladium(II); Methionine sulfoxide; Infrared spectroscopy; 15 N NMR; Antitumor; Cytotoxicity 1. Introduction Platinum(II) complexes and palladium(II) analogues have been prepared and studied as anticancer drugs since Rosenberg in 1965 discovered the antitumoral properties of cisplatin, or cis- diammindichloroplatinum(II) [1]. Cisplatin is particularly effec- tive in treatment of testicular tumors, with a cure rate higher than 95% [2]. It is also used for treatment of ovaries, head and neck cancer [3]. However, cisplatin is also a highly toxic drug. The major side effects of cisplatin are nephrotoxicity, neurotoxicity and also ototoxicity [3]. The interest in developing new drugs that could act as cisplatin but with reduced side effects has stim- ulated the synthesis of many new compounds, including amino acid complexes. Palladium(II) complexes containing S and N donor ligands have been prepared and biological assays showed their activities against several tumor cells (HeLa, 3T3, JURKAT, Pam212 and Pam-ras) [4]. Platinum(II) and palladium(II) com- plexes with phenantroline and amino acids were also described ∗ Corresponding author. Tel.: +55 16 33016630; fax: +55 16 3322 7932. E-mail addresses: pedrocorbi@yahoo.com, pedrcorb@posgrad.iq.unesp.br (P.P. Corbi). and displayed cytotoxic activities on Molt-4, a human leukemia cell line [5]. Indeed, a new palladium(II) complex with the amino acid deoxyalliin was obtained in our laboratories and biological studies have shown its activity against HeLa and TM5 tumori- genic cells [6]. Methionine sulfoxide (C 5 H 11 NO 3 S, metSO) is a sulfur- containing amino acid of vegetal origin present in many natural products of easy access, as carrots and onions [7,8]. Ni(II), Co(II), Cu(II) and Fe(II) complexes with metSO were obtained in our laboratories and previously described [9–11]. Pt(II) and Pt(IV) complexes with metSO were also described in the liter- ature [12]. However, no biological studies were described for such complexes. The present work is dedicated to the synthe- sis, structural characterization and antitumor studies of a new palladium(II) complex with metSO. 2. Experimental 2.1. Reagents and equipments dl-methionine sulfoxide, palladium(II) chloride and lithium(II) chloride were, respectively, Acros, Aldrich and Mall- 1386-1425/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2006.06.003