Detection of saponins in extract of Panax notoginseng by liquid chromatography-electrospray ionisation-mass spectrometry

The liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) method was developed for the analyses and identification of saponins in plant extract from the root of Panax notoginseng (Burk.) F.H. Chen. The HPLC experiments were proceeded by means of a reversed-phase C18 column and a binary mobile phase system consisting of 0.2% acetic acid and acetonitrile under gradient elution conditions. Eight major peaks were separated and detected using both evaporative light scattering and MS detectors. The mass spectrometer was operated in the negative ion mode using electrospray ionization. The molecular ions, [M − H]− and the adduct ions [M + AcO]− of saponins were observed, and from which the molecular weights were obtained. A collision-induced dissociation (CID) experiment was carried out to aid the identification of the backbone and glycosidic linkage sites of the saponins. The identification of the saponins (peaks 1-7) in the extract of P. notoginseng was based on matching their retention times, the detection of the saponin molecular ions, and the fragment ions of the molecular ion obtained in the CID experiments with those of the authentic standards and data reported in the literature. The molecular structure of peak 8 was elucidated according to the fragmentation patterns and the literature reports.