Analysis of Intact Glycosidic Aroma Precursors in Grapes by High-Performance Liquid Chromatography with a Diode Array Detector.

Cristina Cebrián-Tarancón,José Oliva,M Rosario Salinas,Miguel Ángel Cámara,Gonzalo L Alonso

doi:10.3390/foods10010191

Abstract

Nowadays, the techniques for the analysis of glycosidic precursors in grapes involve changes in the glycoside structure or it is necessary the use of very expensive analytical techniques. In this study, we describe for the first time an approach to analyse intact glycosidic aroma precursors in grapes by high-performance liquid chromatography with a diode array detector (HPLC-DAD), a simple and cheap analytical technique that could be used in wineries. Briefly, the skin of Muscat of Alexandria grapes was extracted using a microwave and purified using solid-phase extraction combining Oasis MCX and LiChrolut EN cartridges. In total, 20 compounds were selected by HPLC-DAD at 195 nm and taking as a reference the spectrum of phenyl β-D-glucopyranoside, whose DAD spectrum showed a first shoulder from 190 to 230 nm and a second around 200–360 nm. After that, these glycosidic compounds were identified by High-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (HPLC-qTOF-MS). Disaccharides hexose pentose were the most abundant group observed with respect to the sugars and monoterpendiols the main aglycones found.

Highlights

Aroma glycosides are compounds produced during the secondary metabolism in plants formed by a sugar moiety linked to a volatile aglycone by a β-glycosidic bond
In glycosylated aroma precursors of grapes, the aglycone moiety is responsible for the potential aromatic character of the molecule since, these compounds originally have no odour, the volatile aglycones are released during winemaking contributing to the wine aroma profile [2,3]
Several studies have proven that it is possible to modify the glycosidic aroma profile of grapes by treating the leaves with oak or guaiacol extracts [4,5,6]. Such an important role of glycosylated aroma precursors has stimulated the development of analytical methods for their quantification [7]. Such precursors are analysed by isolating their glycosides, followed by the release of aglycones via enzymatic hydrolysis [8,9] or acidic hydrolysis [10,11,12], and the analysis of volatile aglycones by gas chromatography-mass spectrometry (GC-MS)

Summary

Introduction

Aroma glycosides are compounds produced during the secondary metabolism in plants formed by a sugar moiety linked to a volatile aglycone by a β-glycosidic bond. Several studies have proven that it is possible to modify the glycosidic aroma profile of grapes by treating the leaves with oak or guaiacol extracts [4,5,6] Such an important role of glycosylated aroma precursors has stimulated the development of analytical methods for their quantification [7]. Such precursors are analysed by isolating their glycosides, followed by the release of aglycones via enzymatic hydrolysis [8,9] or acidic hydrolysis [10,11,12], and the analysis of volatile aglycones by gas chromatography-mass spectrometry (GC-MS). In both cases, the molecular structure of glycosylated compounds is modified during the analysis process, a partial breaks occur in the glycosides, generating fragments and causing major structural changes in the aglycones, which do not reflect the original glycoside chemistry of grapes [1,2]

Methods

Results

Conclusion