Abstract
Oxidations of two aliphatic α-amino acids (AA), namely, leucine and isoleucine by hexachloroplatinate (IV) as an anticancer platinum (IV) complex has been studied using a spectrophotometric technique in perchlorate solutions in the presence of palladium (II) catalyst at a constant ionic strength of 1.0 mol dm-3 and at 25°C. The reactions did not proceed in the absence of the catalyst. The reactions of both amino acids showed a first order dependence on both [PtIV] and [PdII], and less than unit order dependences with respect to both [AA] and [H+]. Increasing ionic strength and dielectric constant of the reactions medium increased the rates of the reactions. A probable oxidations mechanism has been suggested and the rate law expression has been derived. Both spectral and kinetic evidences revealed formation of 1:1 intermediate complexes between AA and PdII before the rate-controlling step. The oxidation products of the investigated amino acids were identified as the corresponding aldehyde, ammonium ion and carbon dioxide. The activation parameters of the second order rate constants were evaluated and discussed
Highlights
Anticancer platinum (IV) complexes have attracted many researchers in the last decades [1,2,3,4]
Oxidations of two aliphatic α-amino acids (AA), namely, leucine and isoleucine by hexachloroplatinate (IV) as an anticancer platinum (IV) complex has been studied using a spectrophotometric technique in perchlorate solutions in the presence of palladium (II) catalyst at a constant ionic strength of 1.0 mol dm-3 and at 25°C
The oxidation products of the investigated amino acids were identified as the corresponding aldehyde, ammonium ion and carbon dioxide
Summary
Anticancer platinum (IV) complexes have attracted many researchers in the last decades [1,2,3,4]. Amino acids are subjected to various reactions and supply precursors for many endogenous substances, e.g., haemoglobin in blood. They undergo different reactions, depending on whether a particular amino acid contains non-polar groups or polar substituents. Leucine (Leu) and isoleucine (Ile) (their structure shown below) are essential amino acids They are considered as active site residues of enzymes, and can help in maintaining correct conformation of enzymes by keeping them in their proper ionic states. Their oxidation can help in understanding the enzyme kinetics [16,17,18,19]. The kinetics of oxidation of amino acids is of interest as the products differ depending on the oxidants [20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]
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