Studies Of Polarographic Catalytic Waves Of Quinone And Flavone Compounds

The polarographic catalytic wave of organic compounds is ascribed to the redox cycle that the intermediate free radical produced during the electrochemical reduction process of organic compounds is chemically oxidized by suitable oxidant to regenerate the original. As an important branch of electroanalytical chemistry, polarographic catalytic wave plays an important role in both improving analytical sensitivity and studying kinetic of electrode process. Research on polarographic catalytic wave of organic compounds is, therefore, of great significance for electroanalytical chemistry, biochemistry, organic chemistry and pharmacology.ftavone and quinone compounds have showed strong antitumor, anti-inflammatory and radical-scavenging bioactivities. In this thesis, flavone compound, vitamin P, and quinone compounds, including menadione (vitamin KI) and anti-cancer medicament irisquinone, were chosen as research subjects. Their elctrode reduction processes were investigated in both aqueous and organic media, and their polarographic parallel catalytic waves in the presence of suitable oxidant were observed. The production mechanism of these parallel catalytic waves was elucidated, and analytical methods with higher sensitivity were established. In addition, the host-guest inclusion behavior of irisquinone with /?-cyclodextrin was studied in near physiological condition.This thesis consists of five parts: PART ONEChapter OneAchievement of electrochemical studies of quinone compoundsChapter TwoAchievement of electrochemical studies of flavone and flavonoids compoundsPART TWOThe polarographic catalytic wave of vitamin P in the presence of persulfate was studied by linear potential scan polarography and cyclic voltammetry. Vitamin P yielded a single reduction wave in acidic aqueous solution, which was ascribed to a2e", 2H' reduction process of the carbonyl group in C-4 position. Actually, the carbonyl group C=0 first underwent 1 e", 1H+ reduction to form a neutral free radical, and the further le~, 1H* reduction of the free radical was simultaneous with its following chemical reactions. When SiOg2" was present, the free radical of vitamin P was oxidized by both SiO^2 and its reduction intermediate, sulfate radical anion SO4'", to regenerate the original, which resulted into the production of a polarographic catalytic wave of vitamin P. Based on this catalytic wave, a novel method for the determination of vitamin P was proposed. In 0.02 mol/L tartaric acid-sodium tartrate (pH 3.3) buffer containing S.OxlO"3 mol/L K^SiOg, the peak potential of the catalytic wave was -1.42 V (vs. SCH) and the peak current was rectilinear to the vitamin P concentration in the range of S.OxlO"9 ~ l.OxlO"6 mol/L (r = 0.9994, /; = 13). The catalytic wave of 2.0x10" mol/L vitamin P enhanced the polarographic current 70 times compared with the corresponding reduction wave. The detection limit was 2.Ox IO"9 mol/L, and the relative standard deviation at the 2.0xlO"7 mol/L level was 0.7% (n = 15). The proposed method was used for the determination of vitamin P content in the pharmaceutical preparation of tablets and the medicinal plant Sophora. Japonica L. without previous separation. PART THREEA method for the determination of menadione was proposed. In 0.2 mol/L HOAc-NaOAc (pH 4.7) buffer solution containing 4.0xlO"3 mol/L K1O3, menadione yields a well-defined polarographic catalytic wave with a peak potential -0.95 V (vs. SCE). The second order derivative peak current is linearly proportional to the menadione concentration in the range of 4.0xlO"8 ~ 2.0xlO"6 mol/L with the correlation coefficient of 0.999 (n = 8). The detection limit is 2.0xlO"8 mol/L. The sensitivity of the catalytic wave is 10 times higher than that of the corresponding reduction wave in the absence of KICb The proposed method was used to directly determine the menadione contents in clinical injections in good agreement with the labeled amount without preseparation. The mechanism of polarographic catalytic wave of menadione was discussed. The...