Identification of soyasaponins by liquid chromatography–thermospray mass spectrometry

Abstract

Saponins are important bioactive molecules widespread in the plant kingdom. Soyasaponins, isolated from Glicine max (Leguminosae), have been shown to exhibit various biological activities, e.g., an inhibitory effect on lipid-oxidation and liver-lesion generation and an improving effect on hyper-cholesteremia. Mass spectral investigation of these metabolites requires soft ionization techniques such as desorption chemical ionization, fast atom bombardment and thermospray mass spectrometry. A high-performance liquid chromatographic method was developed for thermospray mass spectrometric analysis of saponins contained in soybean flour extracts. The analyses were performed using a ternary eluent (water–acetonitrile–methanol) in gradient conditions with post-column addition of aqueous ammonium acetate. Six saponin components could be separated and identified. The mass spectra obtained provided information concerning both molecular masses and aglycone composition.