Differentiation of flavonol glucoside and galactoside isomers combining chemical isopropylidenation with liquid chromatography-mass spectrometry analysis.
Flavonol glycosides are important components of leaves from vascular plants. A lot of isomers of these compounds are produced by plants, making their analysis very difficult and causing many structural misinterpretations. Galactosides and glucosides as mono- or oligosaccharides yield many diastereoisomers, hindering the analysis by mass spectrometry. In order to enable the mass spectrometric distinctions of these isomers, in this work we combine an isopropylidene based chemical derivatization with liquid chromatography with multiple-stage mass spectrometry (LC-MS(n)) analysis. The isomers of flavonol triglycosides, after the reaction, yielded products with different molecular weight, therefore, they were no longer isomers, allowing their identification by MS(1) analysis. However, to the 4 isomers of flavonol diglycosides, only one yielded, after isopropylidenation, a product with different molecular weight. To the other 3 species, the incorporation of 2 isopropylidene groups retained them in the isomeric form. For such species, chromatographic separation and MS(n) detection targeting the lithium adducts of 3,4-O-isopropylidene-galactosyl or 4,6-O-isopropylidene-glucosyl residues (m/z 209.099) provided specific MS profile.
Instituto de Pesquisa Pelé Pequeno Príncipe, Faculdades Pequeno Príncipe, 80250-200 Curitiba, Paraná, Brazil; Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, 81531-980 Curitiba, Paraná, Brazil. Electronic address: laurosouza@hotmail.com.
Lauro M
LM
de Souza
Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, 81531-980 Curitiba, Paraná, Brazil.
Nessana
N
Dartora
Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, 81531-980 Curitiba, Paraná, Brazil.
Camila T
CT
Scoparo
Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, 81531-980 Curitiba, Paraná, Brazil.
Philip A J
PA
Gorin
Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, 81531-980 Curitiba, Paraná, Brazil.
Marcello
M
Iacomini
Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, 81531-980 Curitiba, Paraná, Brazil.
Guilherme L
GL
Sassaki
D002853:Chromatography, Liquid; D044948:Flavonols / Q000032:analysis*; D005697:Galactosides / Q000032:analysis; D005960:Glucosides / Q000032:analysis; D006027:Glycosides / Q000032:analysis*; D029755:Maytenus / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry / Q000379:methods
D044948:Flavonols; D005697:Galactosides; D005960:Glucosides; D006027:Glycosides
Glycoside isomers; Isopropylidene; Maytenus ilicifolia; Multiple-stage mass spectrometry; UHPLC–MS