Investigations into the phenolic constituents of dog's mercury (Mercurialis perennis L.) by LC-MS/MS and GC-MS analyses.

INTRODUCTION: Dog's mercury (Mercurialis perennis L.) is a traditional European medicinal plant considered as a rich source of bioactive natural products. Yet phytochemical data of the plant are scant.
OBJECTIVE: This study aimed to identify the hydrophilic phenolic constituents from M. perennis by aqueous and hydroalcoholic extraction.
METHODOLOGY: Extracts of herbal parts were investigated in-depth by HPLC(DAD)-MS/MS and GC/MS analyses. In addition, a novel compound was isolated and fully characterised by 1- and 2D-NMR experiments.
RESULTS: Several conjugates of caffeic, p-coumaric and ferulic acids together with glucaric or 2-hydroxyglutaric acids (depsides) were detected in the aqueous extracts from aerial plant parts by use of LC-MS/MS techniques as well UV-spectral data. By implementation of preparative chromatography on polyamide pretreated with formic acid followed by vacuum liquid chromatography on reversed-phase C(18) -silica, one of the predominant depsides was isolated as a pure compound. The NMR spectra ((1) H and (13) C NMR) together with 2D-hetereonuclear multiple bond correlation NMR experiments (gHMBC and gHSQC) and chiral GC investigation, allowed identification of this compound as (-)-(E)-caffeoyl-2-(R)-oxoglutarate. This structure was additionally supported by GC/MS data after silylation and methylation reactions. The hydroalcoholic extract from aerial parts was separated by solvent partition between ethyl acetate and n-butanol. The latter fraction (n-butanol) yielded a mixture of mono- and oligo-glycosides of kaempferol and quercetin, all of them being assigned by LC-MS/MS.
CONCLUSIONS: The present investigation constitutes the first comprehensive report on the hydrophilic constituents of the rarely studied plant Mercurialis and thus completes the phytochemical knowledge on M. perennis.