Advances in the Dereplication of Aroma Precursors from Grape Juice by Pretreatment with Lead Acetate and Combined HILIC- and RP-HPLC Methods.

Michele D’Ambrosio

doi:10.3390/foods8010028

Abstract

Glycosidic aroma precursors (GAPs) contribute to the varietal flavor of wine. Researchers have applied various sample preparation and analytical methods in attempts to achieve their separation and identification. However, mass spectrometric methods still fail to unequivocally define their structures. We have previously reported the separation of GAPs in their natural form and elucidated their structures by nuclear magnetic resonance (NMR) spectroscopy. In this study, we confirm the effectiveness of our established procedure and present methodological improvements. Grape juice was treated with lead (II) acetate and repeatedly chromatographed to give seven pure GAPs. Their chemical structures were characterized by MSn fragmentations and 1D- and 2D-NMR spectra. Ten GAPs were analyzed by both hydrophilic interaction liquid chromatography (HILIC) and reversed phase high performance liquid chromatography (RP-HPLC) to compare the two chromatograms. A selection of known phenols was treated with lead (II) acetate in order to check its binding properties.

Highlights

The flavor precursors present in grapes and wine comprise a heterogeneous blend of monoand disaccharide glycosides of volatile aglycones, which include monoterpenes, C13 -norisoprenoids, benzene derivatives, and long-chain aliphatic alcohols [1]
Ten Glycosidic aroma precursors (GAPs) were analyzed by both hydrophilic interaction liquid chromatography (HILIC)
The high sensitivity and selectivity of the high-performance liquid chromatography (HPLC) system interfaced to the high-resolution mass spectrometry (HRMS) unit was exploited to characterize the GAPs in grapes [5]

Summary

Introduction

The flavor precursors present in grapes and wine comprise a heterogeneous blend of monoand disaccharide glycosides of volatile aglycones, which include monoterpenes, C13 -norisoprenoids, benzene derivatives, and long-chain aliphatic alcohols [1]. A method using Fourier-transform infrared (FTIR) spectrometry and chemometric techniques allowed the rapid determination of C13 -norisoprenoidic and monoterpene glycoconjugates, with predictive errors of 14% and 15%, respectively [3]. Experiments carried out the identification of glycoconjugates by exhaustive trifluoroacetylation of sugar hydroxyls followed by GC-MS analysis and subsequent comparisons of retention times (tR ) and mass spectra with synthetic standards [4]. The experiments disclosed 20 monoterpene-diglycoside derivatives but could not confirm the structure of isobaric aglycones and their sugar residues

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