Monosaccharides, the most basic units of biologically important carbohydrates, are building blocks of the most important biomolecules including polysaccharides, nuclei acids, glycolipids and glycoproteins. In plants, numerous secondary metabolites conjugate glycosides and form glycosides of terpenoids, steroids and flavonoids, etc. Monosaccharides are commonly including two typical sub-groups, hexoses and pentoses. In order to identify monosaccharides in analyzed samples, terms of isomeric forms have to be clearly addressed. On the aim of determination of monosaccharide in glycosides of secondary metabolites isolated from medicinal plants, an ultra-performance liquid chromatography coupled with a PDA detector and a mass spectrometry (UPLC-UV/MS) method has been developed to characterize d-arabinose, l-arabinose, d-ribose, l-ribose, d-xylose, l-xylose, d-glucose, l-glucose, d-galactose, l-galactose, d-allose, l-allose, d-fucose, l-fucose, l-mannose, l-rhamnose, 2-deoxy-d-glucose, 6-deoxy-d-glucose and 2-deoxy-d-galactose. The separation was achieved by using C-18 column material combined a gradient system. The mobile phase is composed of water and acetonitrile/methanol/isopropanol, both containing formic acid. The column temperature was maintained at 35°C. Before applying individual monosaccharide on UPLC system, each monosaccharide was derivatized [1,2]. The developed method is successfully applied for the analysis of purified compounds cauloside G and ciwujianoside A1 from Blue cohosh (Caulophyllum thalictroides). In these compounds, d-glucose, l-arabinose and l-mannose were identified. This method is also applied for quality assurance of dietary supplements claiming to contain Stevia. From few of the Stevia supplements, d-glucose was identified which should not be present.
Figure: Structures of D/L-glucose derivatives and its extract ions chromatograms of [M+Na]+ at m/z=455
Acknowledgements: This research is supported in part by „Science Based Authentication of Dietary Supplements“ and „Botanical Dietary Supplement Research“ funded by the Food and Drug Administration grant numbers 5U01FD002071–10 and 1U01FD003871–02, and the United States Department of Agriculture, Agricultural Research Service, Specific Cooperative Agreement No. 58–6408–2-0009.
References: [1] Tanaka T, et al. (2007) Chem Pharm Bull, 55: 899–901. [2] Fu X, et al. (2010) Planta Med, 76: 178–181.
