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.