Identification of ginsenosides from Panax ginseng in fractions obtained by high-performance liquid chromatography by field desorption mass spectrometry, multiple internal reflection infrared spectroscopy and thin-layer chromatography

Abstract

The high-performance liquid chromatographic (HPLC) determination of the ginsenoside saponins from Panax ginseng C.a. Meyer (Araliaceae) was used to investigate the possibilities and limitations of peak identification with on-line and off-line methods. Thin-layer chromatography was used to separate the ginsenosides with a running distance of 6.5 cm, the detection limit being 0.2 μg. By means of multiple internal reflection infrared (IR) spectroscopy, IR spectra were obtained with 20 μg of ginsenoside. Field desorption (FD) mass spectrometry permitted not only the identification and determination of the molecular weights of underivatized ginsenosides, but also gave important information about the sequence of the sugar moities in the molecule. Less than 1 μg of ginsenoside is needed to produce an FD spectrum. The time required for the FD investigation of an HPLC fraction containing a ginsenoside is about 1 h, including sample preparation. FD measurements, data processing, output, evaluation and interpretation.