Abstract
Four coordination compounds of Pd(II), Pt(II) and Pt(IV) with usnic acid (H3AU) and 1-(o-tolyl)biguanide (TB) as ligands have been synthesized in view of their potential as antimicrobial, antifungal and antitumor agents. The metal complexes have been characterized by elemental and thermogravimetrical analyses, infrared and electronic spectra. Based on these studies, the following formulas have been proposed for the complexes: [Pd(TB)(H3AU)]PdCl4 (C1), [Pd(TB)(H2AU)] CH3COO (C2), [Pt(TB)(H2AU)Cl2]Cl (C3) and [Pt(TB)(H2AU)]Cl (C4), where H2AU is deprotonated usnic acid. The in vitro biological activities of the new complexes were tested against Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Candida albicans ATCC 10231 and HeLa tumor cells. All complexes were found to have good biological properties and therefore they can be further explored in therapeutic applications.
Highlights
Biguanides and related compounds have remained an important area of research, especially for their wide applications, due to their antibacterial, antifungal, antimalarial, hypoglycemic or antitumor activities [1-8]
In this paper we report the synthesis of four coordination compounds of palladium and platinum with mixed ligands: usnic acid and 1-(o-tolyl)biguanide, as well as their analytical and spectral characterization and biological activity screening
Synthesis of complexes [Pd(TB)(H2AU)]CH3COO (C2) and [Pt(TB)(H2AU)Cl2]Cl (C3): the ligands were dissolved in ethanol, under slight heating; the required metal salt, i.e., Pd(CH3COO)2 and H2PtCl6, respectively, dissolved in a minimal amount of ethanol, was added slowly under stirring, to the solution of the ligands
Summary
Biguanides and related compounds have remained an important area of research, especially for their wide applications, due to their antibacterial, antifungal, antimalarial, hypoglycemic or antitumor activities [1-8]. Biguanides have a remarkable coordination capability to various metal ions and the resulting complexes have often higher biological activity than ligands [9-11]. Some coordination compounds of palladium and platinum with biguanides, such as [Pd(C2H6N5)2]·H2O, [Pd(HDMBG)2]Cl2·H2O, [PdL1]Cl2·0.5H2O and [PdL2]Cl2·1.5H2O (where HDMBG: dimethylbiguanide, L1: C12H28N12, L2: C12H30N14), [Pd(CHX)][PdCl4]·2H2O, [Pd(CHX)](CH3COO)2, [PtC14(C4H11N5)]·C2H6OS (where CHX: chlorhexidine), have been synthesized and tested for their biological activity [12-15]. The usnic acid shows a wide range of biological properties, such as antibiotic, antiviral, antibacterial, apoptotic, analgesic and anti-inflammatory activities [16-27]. Literature survey revealed some metal complexes with usnic acid or its derivatives as ligands [30-34]
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