Molecular structures of metal complexes with mefenamic acid
Introduction
Metal-binding substances, many of which function by chelation, form a class of substances which have provided many useful drugs and other substances of value in selective toxicity. They have found many uses in veterinary and human medicine. Humans require the lighter, and usually more abundant, metals: calcium (Ca) and sodium (Na) which are essential for all living cells [1].
Mefenamic acid is used as an agent against fever, ache and inflammation. Some drugs had been prepared on its basis [2], [3]. It should be noted that infrared and X-ray powder diffraction data on its metal complexes are not plentiful in the literature. Brzyska and Ozga [4] had prepared some complexes of mefenamic acid with rare earth elements and studied their properties by using infrared spectra and diffraction patterns. As it is known, there is a possibility of interaction between the drug and many biologically important metal ions like Na, Ca, etc. present in body fluids. Hence we have extended this study and reported Na and Ca complexes of mefenamic acid. Also, there is some disagreement regarding the assignments of the fundamental groups of mefenamic acid made by Brzyska and Ozga [4]. In our study, some revisions in the assignments have been made according to the literature. Furthermore, in the study of Brzyska and Ozga [4], the peak assignments of the X-ray diffraction patterns of the rare element complexes of mefenamic acid had not been given. In this work, the structures of these complexes were determined using infrared spectra and X-ray powder diffraction patterns with the peak assignments to provide a better understanding of the pharmacological studies.
Section snippets
Material and methods
Light yellow crystals of mefenamic acid from Ponstan Forte tablets were grown by slow evaporation of a solution of the compound in methanol at room temperature. The compounds were prepared in the following manner: Mefenamic acid (0.5 mmol) was dissolved in hot methanol by mixing. Then metal hydroxide solution (0.5 M) was added until pH 7.0 with constant stirring; the compound (light gray) was dried at room temperature for a few days.
The infrared spectra of the samples (Fig. 1) were recorded on
Results and discussion
As far as we know, few vibrational and structural studies have been reported for mefenamic acid molecule (Scheme 1). The infrared spectra and X-ray diffraction patterns of some complexes of mefenamic acid with rare earth elements had been reported by Brzyska and Ozga [4]. They determined the nature of the metal–organic ligand coordination in the complexes and mentioned that in the rare earth element complexes of mefenamic acid, only carboxyl groups take part in the bonding of the metal–organic
Acknowledgements
The authors wish to acknowledge the support of Hacettepe University Research Fund (Project No 97.01.602.003).
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