DETERMINATION OF HYPERICIN AND PSEUDOHYPERICIN BY THIN-LAYER CHROMATOGRAPHY DENSITOMETRY

The accuracy and reproducibility of the determination of hypericin and pseudohypericin by measuring the emitted fluorescence in situ on thin-layer chromatography plates can be improved significantly by using appropriate dipping reagents. The effects of pyridine, polyethylene glycol 4000, paraffins, silicone oil and Triton X-100 in various solvents and combinations on the intensity and stability of emitted fluorescence are described. Using the test conditions established by this investigation, hypericin can be quantified exactly within the range 5-50 ng and pseudohypericin within the range 20-200 ng. The relative standard deviation for the quantification under the given conditions is less than 1.5% for both substances.