title: Approach to the study of flavone di-C-glycosides by high performance liquid chromatography-tandem ion trap mass spectrometry and its application to characterization of flavonoid composition in Viola yedoensis.
abstract: The mass spectrometric (MS) analysis of flavone di-C-glycosides has been a difficult task due to pure standards being unavailable commercially and to that the reported relative intensities of some diagnostic ions varied with MS instruments. In this study, five flavone di-C-glycoside standards from Viola yedoensis have been systematically studied by high performance liquid chromatography-electrospray ionization-tandem ion trap mass spectrometry (HPLC-ESI-IT-MS(n)) in the negative ion mode to analyze their fragmentation patterns. A new MS(2) and MS(3) hierarchical fragmentation for the identification of the sugar nature (hexoses or pentoses) at C-6 and C-8 is presented based on previously established rules of fragmentation. Here, for the first time, we report that the MS(2) and MS(3) structure-diagnostic fragments about the glycosylation types and positions are highly dependent on the configuration of the sugars at C-6 and C-8. The base peak ((0,2) X1 (0,2) X(2)(-) ion) in MS(3) spectra of di-C-glycosides could be used as a diagnostic ion for flavone aglycones. These newly proposed fragmentation behaviors have been successfully applied to the characterization of flavone di-C-glycosides found in V. yedoensis. A total of 35 flavonoid glycosides, including 1 flavone mono-C-hexoside, 2 flavone 6,8-di-C-hexosides, 11 flavone 6,8-di-C-pentosides, 13 flavone 6,8-C-hexosyl-C-pentosides, 5 acetylated flavone C-glycosides and 3 flavonol O-glycosides, were identified or tentatively identified on the base of their UV profiles, MS and MS(n) (n = 5) data, or by comparing with reference substances. Among these, the acetylated flavone C-glycosides were reported from V. yedoensis for the first time.
authors.affiliation: Department of Pharmacognosy, School of Pharmacy, Fudan University, Shanghai, 201203, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Cao
authors.forename: Chengle
authors.initials: C
authors.lastname: Yin
authors.forename: Yan
authors.initials: Y
authors.lastname: Qin
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Cheng
authors.forename: Daofeng
authors.initials: D
authors.lastname: Chen
mesh_terms: D020001:1-Butanol / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005419:Flavonoids / Q000032:analysis* / Q000737:chemistry; D006027:Glycosides / Q000032:analysis* / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry / Q000379:methods*; D032413:Viola / Q000737:chemistry*
chemical_list: D005419:Flavonoids; D006027:Glycosides; D010936:Plant Extracts; D020001:1-Butanol
keywords: LC-MSn; Viola yedoensis; flavone di-C-glycoside; fragmentation; ion trap