Studies On Electrochemistry, Catalytic Kinetics And Electroanalytical Method Of Small Bio/Pharmaceutical Molecules

Some small bio/pharmaceutical molecules play important roles in biological systems. L-Cysteine (L-Cys) is an important element of protein insulin and has many significant functions. Isoniazid is an important drug for the chemotherapy of tuberculosis. It also has special meaning in physiology. Kuh-seng alkaloids have vigorously physiological activity. They have been used to apply as antivirus, anti- inflammation, improvement of immunity and tumour resistants. Different methods of chemical analysis and chemically modified electrodes were developed and reported, but (Ferrocenylmethyl)trimethy- lammonium, (FcM)TMA, as a homogeneous mediator for oxidation of L-Cys and isoniazid were not reported. There are not any literature about the direct electrochemical behaviours and electrochemical determination for Kuh-seng alkaloids and their pharmaceutical products. In order to explore their functions in biological systems, the electrochemical studies for L-Cys, isoniazid and Kushen alkaloids were performed.· The behaviors of electrochemistry and electrochemical kinetics of L-Cys and isoniazid at solid electrode in the presence of (FcM)TMA were studied by cyclic voltammetry, chronoamperometry and square wave voltammetry. The mechanism of electrocatalytic oxidation was also investigated. The experimental results show that, (FcM)TMA is an active homogeneous catalyst for the oxidation of L-Cys and isoniazid. Experimental conditions of the catalyst and catalytic system, which maximize the current efficiency of the electrocatalytic oxidation, such as supporting electrolyte, pH value and scan rate were also investigated. The electrochemical kinetics of reaction system were researched and the reaction order, electron transfer coefficient and rate constant were calculated. The probable mechanism of electrocatalytic oxidation was proposed. The contents of isoniazid pharmaceutical products were determined by SWV, and the values compared with the results of UV.· In a physiological medium, the voltammetric behaviors of Kuh-seng alkaloids: matrine, oxymatrine, sophoridine, and oxysophoridine at glassy carbon electrode were observed by cyclic voltammetry and square wave voltammetry. The influences of pH, scan rate on the peak currents and peak potentials of matrine and sophoridine were investigated. The electrochemical kinetics,which were studied by bulk electrolysis with coulometry, chronocoulometry and chronoamperometry, were used for the calculation of electron transfer number, electron transfer coefficient, diffusion coefficient and rate constant. The research results can be applied in the determination of the contents of commercial matrine injection and matrine, sophoridine pharmaceutial products by square wave voltammetry.