Fluorescence enhancement of flavoxate hydrochloride in alkali solution and its application in pharmaceutical analysis / 药学学报

Fluorescence enhancement reaction of flavoxate hydrochloride (FX) in strong alkali solution was studied, the mechanism of the reaction was investigated, and a novel fluorimetric method for analysis of FX in drug sample was established. FX has no intrinsic fluorescence, but it can slowly produce fluorescence in strong alkali solution. Heating can promote the fluorescence enhancement reaction. In 3D fluorescence spectra of the decomposition product of FX, two fluorescence peaks, located respectively at excitation wavelengths λex/ emission wavelength λem =223/410 nm, and 302/410 nm, were observed. Using quinine sulfate as a reference, fluorescence quantum yield of the decomposition product was measured to be 0.50. The structural characteriza- tion and spectral analysis of the decomposition product reveal that ester bond hydrolysis reaction of FX is firstly occurred during heating process, forming 3-methylflavone-8-carboxylic acid (MFA), then a cleavage reaction of the γ-pyrone ring of MFA occurred, producing α, β-unsaturated ketone. This product includes adjacent hydroxyl benzoic acid group in its molecule, which can form intramolecular hydrogen bond under alkaline condition, so that increase the conjugate degree and enhance the rigidity of the molecule, and thereby cause fluorescence enhancement. Based on this fluorescence enhancement reaction, a fluorimetric method was proposed for the determination of FX. A linear calibration curve covered the concentration range 0.020 3-0.487 µg · mL. The regression equation was I(F) = 23.9 + 5357.3 c, with correlation coefficient r = 0.999 7 (n = 8), detection limit D = 1.1 ng · mL(-1). The method was applied to the analysis of FX tablets, with a spiked recovery rate of 100.2%. The reliability of the method was verified by a UV-spectrophotometric method.

Fluorimetric analysis of camptothecin in Chinese herbal medicine common Camptotheca fruit / 药学学报

Three-dimensional (3D) fluorescence spectra and thin layer fluorescence chromatogram of common Camptotheca fruit (CCF) crude drug, camptothecin (CPT) and 10-hydroxycamptothecin (HCPT) have been studied, and a novel fluorimetric method for determination of CPT in CCF crude drug has been established. In 3D fluorescence spectra, CPT presented 3 fluorescence peaks with excitation wavelengths lambdaex of 215, 255 and 365 nm, separately, and all peaks with emission wavelength lambdaem of 430 nm. HCPT presented 4 fluorescence peaks with lambdaex of 220, 265, 325 and 375 nm, separately, and all peaks with lambdaem of 555 nm. The fluorescence of CPT is much stronger than that of HCPT. Comparison of 3D fluorescence spectra and analysis of thin layer fluorescence chromatogram revealed that the main fluorescent component of CCF is CPT. HCPT and other components basically do not interfere with the fluorescence of CPT. Under the condition of pH 3.0-6.7, CCF aqueous solution can produce strong and steady fluorescence. Using methanol as solvent, the extracting solution of CCF was prepared, and diluted properly with water, then measured fluorescence intensity at lambdaex/lambdaem = 365/430 nm to determine the content of CPT. A linear calibration curve covered the concentration range 0.002 35-0.235 microg x mL(-1). The regression equation was IF = 9 + 30,844 c, with correlation coefficient r = 0.999 (n=9). The method has been applied to the analysis of CPT in a CCF sample, with a result of 0.127% and a spiked recovery rate of 102%. The reliability of the method has been verified by a thin layer chromatography-fluorescence scanning method. Experimental results demonstrated that this method can be used for quality evaluation of CCF crude drug.