Fragmentation pathways of acylated flavonoid diglucuronides from leaves of Medicago truncatula.
BACKGROUND
Flavonoids are important plant compounds occurring in tissues mostly in the form of glycoconjugates. Most frequently the sugar moiety is comprised of mono- or oligosaccharides consisting of common sugars like glucose, rhamnose or galactose. In some plant species the glycosidic moiety contains glucuronic acid and may be acylated by phenylpropenoic acids.


METHODS
Flavonoid glyconjugates were extracted from leaves of Medicago truncatula ecotype R108 and submitted to analysis using high-performance liquid chromatography combined with high-resolution tandem (quadrupole-time of flight, QToF) mass spectrometry.


RESULTS
The studied leaf extracts contained 26 different flavonoid glycosides among which 22 compounds were flavone (apigenin, luteolin, chrysoeriol and tricin) glucuronides and 13 were acylated with aromatic acids (p-coumaric, ferulic or sinapic). The fragmentation pathways observed in positive and negative ion mass spectra differed substantially between each other and from these of flavonoid glycosides which did not contain acidic sugars. The application of high-resolution MS techniques allowed unequivocal differentiation between ions with the same nominal m/z values containing different substituents (e.g. ferulic acid or glucuronic acid). Eleven of the identified flavonoids have not been reported previously in this species.


CONCLUSIONS
The presented unique fragmentation pathways of flavonoid glucuronates enable detection of these compounds in tissue extracts from different plant species.
Marczak
Łukasz
Ł
Institute of Bioorganic Chemistry PAS, Noskowskiego 12/14, 61-704 Poznań, Poland.
Stobiecki
Maciej
M
Jasiński
Michał
M
Oleszek
Wiesław
W
Kachlicki
Piotr
P
D000215:Acylation; D047310:Apigenin / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D003373:Coumaric Acids / Q000032:analysis; D047309:Flavones; D005419:Flavonoids / Q000032:analysis* / Q000737:chemistry; D020719:Glucuronides / Q000032:analysis* / Q000737:chemistry; D047311:Luteolin / Q000032:analysis; D046913:Medicago truncatula / Q000737:chemistry*; D015394:Molecular Structure; D018515:Plant Leaves / Q000737:chemistry*; D053719:Tandem Mass Spectrometry
D003373:Coumaric Acids; D047309:Flavones; D005419:Flavonoids; D020719:Glucuronides; C073734:sinapinic acid; D047310:Apigenin; C004999:ferulic acid; C017769:tricin; D047311:Luteolin; C007054:chrysoeriol