Study And Application On The Electrochemical Voltammetric Behavior Of Electroactive Components In Three Medicinal Plant

Natural medicinal plant resources are richful in China.Effective ingredients of these resources are complex and various, and each effective ingredient has its special pharmacological function, the content of which influences clinical results directly. Therefore, the qualitative and quantitative analysis of effective factors in natural medicinal plant resources has been the research hotspot around the world.Electrochemical voltammetric analysis, a modern instrumental method,at this stage is mainly used in the determination of active ingredients of western medicine and trace elements, however, is less used in traditional Chinese medicine. As a result, using the analysis method of electrochemical voltammetry, this paper studies on the electrochemical voltammetric behavior of TanshinoneⅡA, Icariin and Quercetin at the hanging mercury electrode, gives a preliminary discussion on the electrochemical reaction mechanism, and sets up the analysis method of electrochemical voltammetry for qualitative and quantitative analysis.Finally, this method is applied to determine the content of these ingredients in natural medicinal plants such as Salvia miltiorrhiza Bunge, epimedium and Folium Apocyni Veneti directly, and in comparison with pharmacopoeia method, the result is satisfying. The analytical method is simple, rapid, less sample amount, high sensitivity and flexible, able to do qualitative and quantitative analysis of Chinese patent medicine, synthetic drugs and other natural medicinal plants that have these ingredients.1. The electrochemical voltammetric behavior of TanshinoneⅡA, Icariin and Quercetin was investigated by linear sweep voltammetry, and the best experiment conditions were determined:(1) TanshinoneⅡA has a sensitive reduction peak at the hanging mercury electrode in 0.2 mol·L-1 HAc-NaAc (pH=3.8) buffer solution, the peak potential is-0.228V (vs.Ag/AgCl), the scan potential range is 0V～-1.0V, the accumulation time is 100s, the scan rate is 300 mV·s-1. (2) Icariin has a sensitive reduction peak at the hanging mercury electrode in 0.1 mol·L-1 Na2HPO4-KH2PO4 (pH=6.27) buffer solution, and the peak potential is-1.62V (vs.Ag/AgCl), the scan potential range is-1.0V～-1.75V, the accumulation time is 120s, the scan rate is 300 mV·s-1. (3) Quercetin has a sensitive reduction peak at the hanging mercury electrode in 0.1 mol·L-1 Na2CO3-NaHCO3 (pH=9.51) buffer solution, and the peak potential is-1.33V (vs.Ag/AgCl), the scan potential range is-0.3V～-1.6V, the accumulation time is 100s, the scan rate is 300 mV·s-12. Electrochemical voltammetric analysis was set up as an quantitative analysis method of TanshinoneⅡA, Icariin and Quercetin based on the optimal conditions. (1) The peak current of TanshinoneⅡA at hanging mercury electrode was proportional to its concentration over the range of 5.00×10-6～2.00×10-5 mol·L-1 (r=0.9994). The detection limit was 2.70×10-7 mol·L-1. This method can be used directly for the determination of TanshinoneⅡA in Salviamiltiorrhiza Bge, the average recovery is 99.4%, RSD is 0.66%. (2) The peak current of Icariin at hanging mercury electrode was proportional to its concentration over the range of 2.50×10-7～2.00×10-6 mol·L-1. The line regression mathematical equation is ip=0.0789c+0.9489 (r=0.9994). The detection limit was 3.50×10-8 mol-L-1. This method can be used directly for the determination of Icariin in epimedium, the average recovery is 97.6%, RSD is 0.83%. Then it was compared with pharmacopoeia method, the result was satisfing. (3) The peak current of Quercetin at hanging mercury electrode was proportional to the concentration over the range of 2.00×10-6～2.00×10-5 mol·L-1 (r=0.9989). The detection limit was 3.50×10-8 mol·L-1. This method can be used directly for the determination of Quercetin in Folium Apocyni Veneti, the average recovery is 97.6%, RSD is 0.56%.3. The electrochemical reaction mechanism of TanshinoneⅡA, Icariin, and Quercetin at the hanging mercury electrode was investigated preliminary by cyclic voltammetry and continuous cyclic voltammetry. The results show that:(1) The electrochemical reaction process of Tanshinone IIA at the hanging mercury electrode is reversible that with reactant adsorption, resultant proliferation and two-electron two-proton transfer.(2) The electrochemical reaction process of Icariin at the hanging mercury electrode is irreversible that with obvious reactant adsorption and two-electron transfer.(3) The electrode reaction process of Quercetin at the hanging mercury electrode is quasi-reversible that with obvious reactant adsorption and two-electron transfer.The results show that:the analysis method of electrochemical voltammetry can be used for the study of electrochemical voltammetric behavior, electrochemical reaction mechanism and qualitative and quantitative analysis of effective electroactive ingredients in natural medicinal plants. The determination method for Electrochemical Voltammetry of TanshinoneⅡA, Icariin, and Quercetin not only provides research foundation for the qualitative and quantitative analysis of effective electroactive ingredients in natural medicinal plants, but also offers theoretical basis for the electrochemical reaction mechanism and kinetics.