Determination Of Paeonol, Protocatechuic Acid And Gallic Acid In Chinese Medicines By Borax Or Aluminum Ion Sensitized Fluorescence

Fluorescence and absorption spectra of paeonol, protocatechuic acid and gallic acid, and their complexes with borax or aluminum ion, have been studied. These compounds can react with borax or aluminum ion to form fluorescent complexes under suitable conditions, resulted in remarkable fluorescence enhancement. Based on the sensitized fluorescence, new methods for the analysis of these compounds in Chinese herbal medicines were proposed.The main contents of the thesis were as follows:1. Spectral properties of paeonol, an active component of Chinese herbal medicine Radix Cynanchi Paniculati (RCP, Xuchangqing), were studied. The native fluorescence of paeonol was very week. In HAc-NaAc buffer with pH 4.4, paeonol can react with AlCl3 to form a fluorescent complex, resulted in a fluorescence enhancement. The fluorescence excitation and emission wavelengths of the Al(â…¢)-paeonol complex were 296 nm and 455 nm, respectively. Fluorescence quantum yield of the complex was measured to be 0.053. Based on the fluorescent reaction, a new fluorimetric method for the determination of paeonol in RCP was proposed. The detection limit of the method was 0.23 ng ml-1. The content of paeonol in RCP sample was determined to be 1.00% by the new method.2. Protocatechuic acid was an active component of Chinese herbal medicine Trachycarpus. fortunei.H. Wendl. (THW, Zonglvzi). Its native fluorescence was very weak. Both addition of borax or AlCl3 to protocatechuic acid solution resulted in enhanced fluorescence. The experimental conditions for the fluorescent reaction were optimized. Fluorescence quantum yields of the two fluorescent complexes were measured to be 0.107 and 0.053, respectively. Based on the fluorescent reactions, new fluorimetric methods for the determination of protocatechuic acid in THW were proposed. The detection limits of the methods were 0.17 and 0.36 ng ml-1, respectively. The content of protocatechuic acid in THW sample was determined to be 0.0705% by using the new methods.3. Spectral properties of gallic acid, an active component of Chinese herbal medicine Radix Paeonlae Rubra (RPR, Chuanchishao), were studied. The native fluorescence of gallic acid was very week. Both addition of borax or AlCl3 to gallic acid solution resulted in sensitized fluorescence. The experimental conditions for the fluorescent reaction were optimized. Fluorescence quantum yields of the two fluorescent complexes were measured to be 0.066 and 0.049, respectively. Based on the fluorescent reactions, two fluorimetric methods for the determination of gallic acid in RPR were proposed. The detection limits of the methods were 0.19 and 0.33 ng ml-1, respectively. The content of gallic acid in RPR sample was determined to be 1.18% by the new methods.