X-ray powder diffraction analysis of methionine sulfoxide

Methionine sulfoxide (MetSO, C5HnNO3S, Figure 1), a product of vegetal origin, is an amino acid similar to methionine. It is present in garlic (Sugii et al., 1964), onion (Kuon and Bernhard, 1963), nut (Kristensen et al, 1974), carrot (Alabran and Mabrouk, 1973), apple (BielinskaCzarnecka, 1963; McKee and Urbach, 1953), and banana plant (Steward et al., 1960). Recently, methionine sulfoxide was shown to be associated with Alzheimer's disease, due to glutamine synthetase inhibition. This process is accomplished through a free radical oxidation stress. Therefore, the compound is considered a biological sensor for such transformation (Chao et al., 1997; Haghighi and Maples, 1996). This amino acid, readily available and of low cost, was also shown to possess pronounced antiinfiammatory effects (Unnikrishnan and Rao, 1990). In this context, the ligand and its transition metal complexes are of interest for research in order to obtain virtual chemical vehicles for safer drugs, pharmaceutical trappers, or even antidotes for the cases of acute poisonings. Metal (II) complexes of the first transition series involving DL-methionine-sulfoxide have been studied in our laboratories recently (Corbi et al., 2000). The present work is dedicated to the characterization of the amino acid methionine sulfoxide by using X-ray powder diffractometry.