| Chinese herbal medicines (CHMs) have played an important role in clinical therapy for many diseases, especially as a valuable, readily available resource for healthcare in some oriental countries for thousands of years.The usage of CHMs has expanded globally and CHMs have been gaining ever-increasing interest and acceptance in many different countries. The considerable scientific significance and commercial potential of CHMs result in more and more international attention and global market demands.Electrochemical methods offer improved analytical characteristics such as short analytical time, little reagent consumption, easy operation and environmental friendly. More inadequate, the pharmacological action and reaction mechanism of medicine can be observed using these methods. So, it is very important to develop a rapid, high sensitivity method to detect the main active content in CHMs and investigate the mechanisms occurring in pharmacological actions. In this thesis, we have done some work in this field and the main results are expressed as follows:1. The voltammetric behavior of salvianic acid A sodium (SAS), was studied by cyclic voltammetry (CV), chronocoulometry, and differential pulse voltammetric (DPV)for the first time. In pH 3.3 britton-robinson (B-R) buffer solution, the medicine showed a pair of quasi-reversible redox peaks. It was found that the electrode reaction of SAS was driven by adsorption and involved two electrons and two protons transfer process. The dynamics parameters of electrode process were investigated and the reaction mechanism was proposed. Based on understanding the electrochemical process of SAS at the glassy carbon electrode (GCE), analysis of SAS can be realized. The oxidation peak currents showed linear relationship with the concentrations of SAS in the range of 5.45×10-8 to 1.09×10-5 M. The limit of detection was 5.45×10-8 M. The proposed method has high sensitivity, good precision, wide linear range, and was successfully applied to quantitative determination of the SAS in Rukuaixiao Tablets.2. In pH 7.4 phosphate buffer solution (PBS), rosmarinic acid (RA) exhibited two pairs of reversible redox peaks with surface electrode process. A value of 1.15×10-12mol/mm2 was calculated as the saturated adsorption (ΓT) of RA on the electrode surface and there were four electrons and four protons took part in the electrode reaction. Then the mechanism of electrode reaction was proposed. Under optimal conditions, the peak current showed linear dependence on the concentration of RA in the range of 3.0×10-9 to 1.0×10-6 M (r=0.9989) with a detection limit of 3.0x10-9 M. The current method was successfully applied to quantitative determination of RA in Prunella vulgaris with relatively simple extraction procedure. The recovery studied gave values from 97.90% to 105.18%.3. A highly sensitive electrochemical sensor of methotrexate has been designed. DNA molecules and Single- walled carbon nanotubes are immobilized onto a pretreated glassy carbon electrode (GCE(ox)) surface. The oxidation of methotrexate is an irreversible adsorption-controlled process on the modified electrode. The oxidation mechanism was proposed and discussed in this work. It was found that in the range of 6.0×10-8- 2.0×10-5 M, the currents measured by square-wave voltammetry presented a good linear property as a function of the concentrations of methotrexate. The proposed method was also successfully applied for the determination of methotrexate in human blood serum with good satisfactory. |
PDF Full Text Request