Parallel enrichment of polyphenols and phytosterols from Pinot noir grape seeds with molecularly imprinted polymers and analysis by capillary high-performance liquid chromatography electrospray ionisation tandem mass spectrometry

Abstract

This investigation describes an integrated workflow for the parallel extraction and recovery of polyphenols and phytosterols from Pinot noir grape seeds. Using (E)-resveratrol and stigmasterol as exemplars, the approach employs two different molecular imprinted polymers in tandem for the extraction of these compounds and their subsequent analysis by capillary high-performance liquid chromatography (capHPLC) interfaced with electrospray ionisation tandem mass spectrometry (ESI MS/MS). Information on the selectivity of the solid-phase extraction processes was obtained through analysis of the binding behaviour of (E)-resveratrol- and stigmasterol-imprinted polymers using structurally similar polyphenols or phytosterols with the extent of binding determined from the capHPLC-ion trap ESI MS/MS data. This study documents with Pinot noir grape seed extracts and optimised solid-phase extraction protocols that the (E)-resveratrol-templated MIP enabled a very high recovery (99%) of the health-beneficial polyphenol (E)-resveratrol with co-purification of procyanidin and catechin/epicatechin. Further, the stigmasteryl-3-O-methacrylate-templated polymer resulted in high recovery (96%) of the phytosterol stigmasterol with co-purification of campesteryl glycoside. The results also demonstrate that rapid and high-resolution capHPLC-ESI MS/MS methods can be used as part of the work flow for selectivity optimisation and monitoring of the performance of MIPs intended for use in the solid-phase extraction of bioactive molecules with nutraceutical properties from agricultural waste streams.

Keywords: Covalent and non-covalent imprinting; Molecularly imprinted polymers; Phytosterols; Polyphenols; Solid-phase extraction.