ANALYSIS OF DIGITALIS LEAVES Ⅰ. THIN LAYER CHROMATOGRAPHY OF DIGITALIS GLYCOSIDES

Nine adsorbents and 139 solvent systems were studied for the adsorption thin layer chromatographic separation of digitalis glycosides, but only partial separation was ob- tained. Better results were observed with partition thin layer chromatography. The glass plate (18×5cm) was coated with a slurry of 1.3 g kieselguhr, 0.2 g gypsum, and 6.3 ml water, dried for 1 hr at room temperature and 1 hr at 120℃.The plate was then developed with a solution of 1.5 g formamide in 10 ml acetone or sprayed with a 10% formamide solution in acetone, in such amount as to make each plate hold 0.8-0.9 g formamide. Suitable amount of glycoside dissolved in chloroform-methanol mixture (1:1) was applied to the plate, and the chromatogram was developed with a formamide-saturated solvent; when the solvent reached the top, the plate was taken out and heated for 20 min at 120℃ to remove formamide, then sprayed with 50% sulphuric acid immediately, the glycosides were seen as differently coloured spots. The following solvent systems gave the best separation: Chloroform-acetone-ethyl acetate-formamide (5:2:3: saturated) ; chloroform-acetone-ethyl acetate-ethanol-formamide (8:2:0.5: 0.5: saturated) ; chloroform-benzene-ethyl acetate-formamide (1:2: 3: saturated) ; chloroform-butylalcohol-formamide (9:1: saturated).