Elucidation of glycosylation sites of kaempferol di-O-glycosides from methanolic extract of the leaves of Prunus domestica subsp. syriaca

Abstract

Rationale: Flavonol glycosides containing the glycosylation patterns 3,4'-di-O and 4',7-di-O are rare in nature and they have not yet been studied in detail by electrospray ionization mass spectrometry (ESI-MS(+/-), in contrast to the flavonol glycosides containing the glycosylation pattern 3,7-di-O.

Method: The leaves from Prunus domestica L. subsp. syriaca were extracted with pure methanol or, in order to perform hydrolysis and extraction simultaneously, with a 5% methanolic solution of hydrochloric acid. The high-performance liquid chromatography (HPLC)/ESI-MS(+/-) analyses were performed using a Waters model 2690 HPLC pump and a Waters/Micromass ZQ2000 mass spectrometer.

Results: Three kinds of kaempferol di-O-glycosides have been identified, namely kaempferol-3-O-hexoside-7-O-rhamnosides, kaempferol-3-O-pentoside-4'-O-rhamnosides and kaempferol 4',7-di-O-rhamnoside. The identification was performed on the basis of the abundances of the respective Y-type product ions.

Conclusions: The abundances of [Yⁿ ₀ - H]^-· , Yⁿ ₀ ^- and Yⁿ ₀ ⁺ product ions were of crucial importance for the determination of glycosylation patterns. The obtained results can be useful for HPLC/ESI-MS identification of rare flavonol-di-O-glycosides.