QUANTITATIVE TLC-DENSITOMETRY OF COUMARINS IN QIN PI (FRAXINUS STYLOSA)

We have reported previously, the isolation of four coumarins and a phenolic glycoside from Qin Pi (Fraxinus stylosa). This paper deals with the TLC-densitometry of the coumarins in the drug. Fraxetin, esculetin, fraxin, esculin and stylosin were separated on silica gel G thin layer, 25 ml of the lower layer of choroform-methanol-water (30:10:3) plus 0.5 ml of formic acid were used as developing solvent. Densitometric determination was carried out with a Shimadzu dual-wavelength TLC scanner CS-910 and the spot areas were determined and recorded by the Chromatopac C-E 1B data processor. The parameters for the linearization of working curves were: λ_s=340nm, λ_R=440nm, reflectance mode, zig-zag scanning, S_x=3, working curves were obtained, all passing through the origin.The method has been applied to the analysis of various samples, including those from different sources, of different parts of the plant and of different collecting seasons.The procedure was simple and rapid, the results were stable and reproducible. The coefficient of variation was 1.2～2.8%.