A.M.L. Da Silva’s scientific contributions

The effects of zinc-methionine complexes with molar relation 1:1 and 1:2 have been examined as nutritional supplements in rats. The synthesis and characterization of two compounds were studied by elemental analysis and FTIR. The bioavailability effect was studied by zinc retention and its content in rat tissues in rats fed with different zinc-methionine complexes. The compound 1:1 was a cation complex of formula [Zn(C5H10NO 2S)(H2O)2]+, very water soluble, while the compound 1:2 was a neutral complex of formule [Zn(C5H 10NO2S]2], only soluble in pH below 3. FTIR spectra of both complexes show strong absorption bands due to C-O stretching of the amino acid group (ranging from νs(C=O) 1638 cm-1 and νas(C-O) 1414 cm-1, in ZnMet, to νs(C=O) 1608 cm-1 and νas(C-O) 1426 cm-1, in Zn(Met)2) shifted significantly with respect to the ones observed for the free methionine (νas(COO) 1582 cm -1 and νs(COO) 1415 cm-1,1720 cm -1). The nutritional result in the zinc fecal elimination of the animals of the control group was significantly different (P < 0.05) to the ones observed for the animals treaties with zinc supplemented diets, though this was not observed during urinary elimination. This study indicates that the content of zinc in the feces collected in 14 days for all zinc diet were significantly different (P<0.05) from the control group (animals treaties with zinc practically absent). The retention of zinc in the groups treated with the methionine compounds was significantly higher than the ones fed with ZnSO4 and ZnO diet. In conclusion, these data indicate that the use of zinc-methionine chelates is a valuable tool to increase bioavailability of zinc, however without significant differences between ZnMet and Zn(Met) 2.