Pressurised liquid extraction of arylbutanoid and diarylheptanoid glycosides from Betula pubescens phloem

Birch phloem (inner bark) is primarily burned as waste in the pulp and paper, forestry and wood processing industries. However, phloem represents a valuable source of biologically active plant secondary metabolites. In this study, we propose new optimised approach for the pressurised liquid extraction of arylbutanoid and diarylheptanoid glycosides from birch (Betula pubescens) phloem. The influence of solvent composition, extraction temperature, extraction time and plant-to-extractant on the extraction of analytes from birch phloem by the pressurised liquid extraction was studied. The optimal conditions of the developed approach were determined as: 70% aqueous methanol at 100 °C in a single 10-minute cycle and the ratio of plant sample to extraction cell volume of 1 g to 10 mL. Pure compounds of rhododendrin apioside, rhododendrin, platyphylloside apioside, platyphylloside, aceroside VIII apioside, aceroside VIII and aceroside VII were obtained from birch phloem extract using preparative high-performance liquid chromatography.