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Spectroelectrochemical and Electroanalytical Study of Fisetin and Luteolin

Author: QiFang
Tutor: HeJianBo
School: Hefei University of Technology
Course: Applied Chemistry
Keywords: Fisetin Luteolin Solid carbon paste electrode Spectroelectrochemical 2 - Amino - 5 - mercapto-1 , 3 , 4 - thiadiazole
CLC: O657.1
Type: Master's thesis
Year: 2010
Downloads: 63
Quote: 0
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Abstract

Flavonoids (Flavonoid) compounds are widely present in vegetables, fruits, pasture and medicinal plants, is the most widely distributed plant components polyphenolic compounds. Luteolin (Luteolin) and fisetin (Fisetin), are an important natural flavonoid antioxidants, anti-oxidation and removal of free radicals, anti-cancer and anti-tumor, anti-cardiovascular diseases, anti-virus and other human body a useful role. Therefore, they are life science and food science research and aroused extensive attention of scholars at home and abroad. In this paper, these two compounds as model compounds, respectively, using electrochemical methods (In suit UV / Vis) spectroscopy in situ UV - visible electrochemical methods and cyclic voltammetry suck (CVA) in paraffin - graphite carbon paste electrode (CPE) tested on their electric redox behavior and spectral changes of the C ring mechanism of electro-oxidation of the 3-OH on flavonoids and antioxidant properties, and modified conductive polymer film the CPE substrate electrode on the two flavonoids simultaneous electrochemical detection. The electrochemical test results show that luteolin and fisetin CPE surface by adsorption and diffusion control, and lower potential two substances have a quasi-reversible oxidation reduction peak A1 and C1 corresponding two by B on the ring 3 ', 4'-dihydroxy-two-electron and a two-proton reaction. Through the comparison of the behavior of the two substances, cyclic voltammetry (CV), confirmed the presence of the 3-OH C ring flavonoids important reason for the occurrence of a subsequent chemical conversion, and can accelerate the rate of reaction of the first step to electrochemical oxidation as well as to improve antioxidant capacity of the material. Found by inspection on the pH value, the pH of the electrolyte is reduced CV peak current can be significantly enhanced, and the peak shape. Unmodified CPE using differential pulse voltammetry of the luteolin and Fisetin BR buffer pH 1.8 trace detection, their linear range of 5 × 10-7 - 1 × 10 -4 mol · L-1 and 3 × 10-7 - 1 × 10-4 mol · L-1, the lowest detection limit reached 4 × 10-8 and 3 × 10-8 mol · L-1 (S / N = 3). Site in situ thin layer of UV / Vis spectra electrochemical tests show that, under different constant potential redox, luteolin and Fisetin the UV / Vis characteristic absorption peak showed a different trend, corresponding to the two substances the carbocyclic on the oxidation and reduction of the hydroxyl groups on the different positions. Then three features of luteolin absorption wavelength study luteolin and its oxidation products concentration by cyclic volt suction method. Each liquid component in the course of the reaction involved in the adsorption and desorption, and the chemical conversion step information is obtained through this pathway. The results show that the pre-adsorbed and solution state luteolin are involved in the electro-oxidation reaction, the oxidation process is mainly controlled by the adsorption, oxidation of the final results generated o-quinone structure. Solid carbon paste electrode as a base material, 2 - amino -5 - mercapto-1, 3, 4 - thiadiazole (AMT), electro-polymerization, making the high sensitivity PAMT / sCPE ampere sensor. By using scanning electron microscopy (SEM), in situ UV / Vis spectroelectrochemical and electrochemical impedance spectroscopy (EIS) were used to investigate deposited on the membrane surface morphology of the surface of the base material AMT the polymer (PAMT) is the polymerization mechanism and charge transfer performance . Experimental results show that the surface of the base material, PAMT film covering paraffin portion prior to the graphite part, and obtained with the increase in the amount of PAMT deposition sensor of the charge transfer resistance is significantly reduced. Physiological pH conditions in the human body, the sensor for the same with the same electrically active portion isomers? Luteolin and Fisetin has high sensitivity and good CV signal separation. Sensor for Lut and Fis amps sensitivity within the concentration range of 10 - 700 nmol · L-1, respectively, 1.41 and 0.648 nA · (nmol · L-1) -1 · cm-2, the lowest detection limit were 3 and 5 nmol · L-1. This study demonstrates that the solid carbon paste electrode base material suitable for as PAMT film sensor. In addition, the use of PAMT / sCPE electrode for the simultaneous detection of quercetin, luteolin and galangin. By comparing Que changes the Lut and Gal three substances in the bare sCPE PAMT / sCPE on CV, PAMT / sCPE anodic peak current of the three substances are significantly improved. When using the the DPV method of detecting when observed to three substances will exist at higher concentrations or low competitive adsorption, so that the method can not be simultaneously detected. When using amperometric current method in simultaneous detection PAMT / sCPE less mutual interference between the three substances obtained Que, the the Lut and Gal lowest detection limit were 2,3 and 1.2 nmol · L-1 (S / N = 3).

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