科研之友
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摘要
Fluorescence and absorption spectra of magnoflorine (MAG) were studied. The effects of environmental factors such as pH on fluorescence and absorbance were investigated , and the relationship between spectral properties and molecular structure was revealed. Three fluorescent peaks appeared in the three-dimensional (3D) fluorescence spectra of the aqueous solution of MAG, with excitation wavelengths (lambda(ex)) of 230 , 275 and 315 nm , and the same emission wavelength (lambda(em)) of 420 nm. As the pH of the solution increased , the fluorescence peak in the excitation spectrum red-shifted and an equal fluorescence point appeared, and the absorption peak in the absorption spectrum also red-shifted and an isosbestic point formed , indicating that proton ionization occurred in one hydroxyl group in the MAG molecule. The proton ionization constant (pK(a) = 4. 77) of MAG was determined by a pH-absorption method. Using L-tryptophan as a reference, the fluorescence quantum yield of the aqueous solution of MAG was determined to be Y=0. 19. The characteristic fluorescence peaks of MAG appeared in the 3D fluorescence spectra of various Chinese herbal medicines. Using methanol-water mixed solvent containing 60% methanol, the extract of Sinomenium acutum (Qingfengteng) was prepared and diluted with water, then 3D fluorescence spectra were obtained. It was observed that the fluorescence peak at lambda e(x)/lambda(em) = 315 nm/420 nm in the spectrum of the Qingfengteng neutral aqueous solution was not affected by the coexisting components. Based on this, a method for the determination of MAG in Qingfengteng was established. In the range of 0. 04 -1. 25 mu g/mL , the regression equation 14 fluorescence intensity (I-F) and MAG concentration (c) was I-F = 6146. 8c + 24.4 , ( R = 0.999 , n = 11 ) , with a detection limit of 0. 52 ng/mL. The content of MAG in the Qingfengteng reference material was determined to be 0.63% by the method , and the recoveries were 101.2%-102.7% . The content of MAG (0. 61% ) in the same sample was also determined by LC-MS/MS method, which was consistent with the fluorescence method.
- 出版日期2019-6
- 单位河北师范大学; 河北工业职业技术学院
