Poster Presenter

Preparation And Kinetic Of Oxidation Of Chromium (III) Binary Complexes Involving Antiparkinson Drugs
Ahmed A. Abdel-Khalek and Mahmoud M. Abdel- Hafeez
Egypt

Parkinson disease is one of the neurodegenerative diseases of the central nervous system (CNS) which caused by the progressive loss of brain cells (neurones) in a part of the brain called the substantia nigra, which produces the chemical dopamine. So, it must be medicated with drugs contain Levodopa (LD) combined with certain amount of carbidopa (CD), which makes LD available for transport to the brain and converted to dopamine in the basal ganglia.

Chromium(III) is probably taken up by the cells by phagocytosis or by forming complex with organic ligands to penetrate the cell membrane.

In this study, 1:1 binary complexes of Chromium(III) with levodopa and carbidopa have been prepared and characterized by different methods. The structures of these complexes can formulate as [CrIII(LD)(OH)2(H2O)2] and [CrIII(CD)(OH)2(H2O)3].7H2O, respectively. By using potentiodynamic technique it is founded that the complex [CrIII(LD)(OH)2(H2O)2] is more stable than [CrIII(CD)(OH)2(H2O)3].

Kinetic studies on oxidation of the prepared binary complexes with N-Bromosuccinimide (NBS) have been investigated.

The rate of oxidation of [CrIII(LD)(OH)2(H2O)2] increases with [NBS], [complex] , pH of the medium, temperature and by using Mn(II) as catalyst. Thermodynamic activation parameters are determined. From these studies, it is concluded that the reaction obeys the rate law:-

d [Cr VI] / d t= k3 K1K2( 1 / [H+] )[NBS] [CrIII(LD)(OH)2(H2O)2]

Whereas the rate of oxidation of [CrIII(CD)(OH)2(H2O)3] undergo the law:

Rate = {k5 [MnII] + (k4 + k3 / [H+])[NBS] }[CrIII(CD)(OH)2(H2O)3]

A suggested mechanisms for the oxidation process have been proposed, in which the reaction proceeds through formation of chromium(IV) and chromium(V) to the final oxidation product chromium(VI). In vivo, it is reported that 30% of carbidopa after its oral administration remain unchanged. Levodopa and carbidopa can form these binary complexes with chromium(III). Moreover, it can be predicted that such complexes may undergo oxidation inside the body providing very reactive species chromium(IV) and chromium(V), (which can be stabilized by intracellular ligands) and reactive oxygen radicals. Both of these intermediates can alterate DNA. Chromium(VI) compounds are well known to be potent toxic and carcinogenic agents. These probabilities require further investigation.