Data-directed scan sequence for the general assignment of C-glycosylflavone O-glycosides in plant extracts by liquid chromatography-ion trap mass spectrometry

• Published in: Journal of Chromatography A 2006-02, Vol.1104 (1), p.123-131
• Main Authors: Kite, Geoffrey C., Porter, Elaine A., Denison, Fiona C., Grayer, Renée J., Veitch, Nigel C., Butler, Ian, Simmonds, Monique S.J.
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Biological and medical sciences; C-Glycosylflavone O-glycosides; C-Glycosylflavones; Chemical constitution; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography, Liquid - methods; Exact sciences and technology; Flavone C-glycosides; Flavones - chemistry; Fundamental and applied biological sciences. Psychology; General pharmacology; Glycosides - chemistry; Isoorientin; Isoschaftoside; Isovitexin; Magnetic Resonance Spectroscopy; Mass Spectrometry - methods; Medical sciences; Multiflorin A; Multiflorin B; Orientin; Other chromatographic methods; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; Plant Extracts - chemistry; Plant physiology and development; Schaftoside; Vitexin
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2005.11.070

An ion trap LC–MS/MS method is described for the analysis of C-glycosylflavone O-glycosides in crude methanolic extracts of plants. The method employs survey scans with and without the application of up-front collision induced dissociation (CID) to generate diagnostic ions for data-directed MS/MS. The spectra acquired allow assignment of the C-linked sugar to either the C-6 or C-8 position of the aglycone and provide data on the molecular mass of the compound, the number and type of O-linked sugars and the molecular mass of the flavone aglycone. These data for the majority of C-glycosylflavone O-glycosides in an extract are obtained automatically in one LC–MS/MS analysis without manual pre-programming. Key to the assignment of the C-6 or C-8 site of C-glycosylation is the generation, by up-front CID, of the 0,1X + product ion formed by internal cleavage of the C-linked sugar. MS/MS of this ion is found to have diagnostic value in addition to the 0,2X + product ion described by other authors. Ion trap MS/MS spectra of [M + H] + of the 6,8-di- C-glycosylflavones schaftoside and isoschaftoside show an additional and previously unreported diagnostic product ion that is useful in determining the type of sugar at the C-6 position. The product ion spectra of protonated kaempferol 3- O-glucosylrhamnosides show similarities to the spectra of C-glycosylflavone O-glycosides; this is a potential source of confusion if the analysis of such glycosides is limited solely to MS/MS of [M + H] +.