Structural elucidation of alfalfa root saponins by mass spectrometry and nuclear magnetic resonance analysis

摘要: Structures of saponins may be fully elucidated using a combination n.m.r. and m.s. instead the usual degradation techniques. Well resolved proton spectra chromatographic separation can obtained from peracetylated mixtures saponins. Under these conditions, genins are identified mainly by 13C spectroscopy; sugars their points attachment determined examining 1H chemical shifts coupling constants following assignments made 2D COSY relayed experiments. Sugar chains sequenced observing intersugar connectivities through long-range couplings (delayed COSY) or n.o.e. Alternatively, use Californium plasma desorption provides quasimolecular ions fragments corresponding to sequential rupture chain sugars. Free carboxylic acids located on an acetylated saponin looking at disappearance, in presence Eu complexes, carbon situated α carbonyl spectrum. The above methods have been employed determine structures seven major alfalfa root, which allegedly responsible for antifeedant properties vegetable.