Methyl Salicylate Glycosides in Some Italian Varietal Wines.

Carlin Carlin,Guella Guella,Masuero Masuero,Mattivi Mattivi,Vrhovsek Vrhovsek

doi:10.3390/molecules24183260

Carlin Carlin, Guella Guella + Show 3 more

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https://doi.org/10.3390/molecules24183260

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Abstract

Glycosides are ubiquitous plant secondary metabolites consisting of a non-sugar component called an aglycone, attached to one or more sugars. One of the most interesting aglycones in grapes and wine is methyl salicylate (MeSA), an organic ester naturally produced by many plants, particularly wintergreens. To date, nine different MeSA glycosides from plants have been reported, mainly spread over the genera Gaultheria, Camellia, Polygala, Filipendula, and Passiflora. From a sensorial point of view, MeSA has a balsamic-sweet odor, known as Wintergreen. MeSA was found in Vitis riparia grapes, in Vitis vinifera sp. and in the Frontenac interspecific hybrid. We found that the MeSA glycosides content in Verdicchio wines and in some genetically related varieties (Trebbiano di Soave and Trebbiano di Lugana) was very high. In order to understand which glycosides were present in wine, the methanolic extract of Verdicchio wine was injected into a UPLC-Q-TOF-HDMS and compared to the extracts of different plants rich in such glycosides. Using pure standards, we confirmed the existence of two glycosides in wine: MeSA 2-O-β-d-glucoside and MeSA 2-O-β-d-xylopyranosyl (1-6) β-d-glucopyranoside (gaultherin). For the first time, we also tentatively identified other diglycosides in wine: MeSA 2-O-α-l-arabinopyranosyl (1-6)-β-d-glucopyranoside (violutoside) and MeSA 2-O-β-d-apiofuranosyl (1-6)-β-d-glucopyranoside (canthoside A), MeSA 2-O-β-d-glucopyranosyl (1-6)-O-β-d-glucopyranoside (gentiobioside) and MeSA 2-O-α-l-rhamnopyranosyl (1-6)-β-d-glucopyranoside (rutinoside). Some of these glycosides have been isolated from Gaultheria procumbens leaves by preparative liquid chromatography and structurally annotated by 1H- and 13C-NMR analysis. Two of the peaks isolated from Gaultheria procumbens leaves, namely MeSA sambubioside and MeSA sophoroside, were herein observed for the first time. Six MeSA glycosides were quantified in 64 Italian white wines, highlighting the peculiar content and pattern in Verdicchio wines and related cultivars. The total concentration in bound and free MeSA in Verdicchio wines varied in the range of 456–9796 μg/L and 5.5–143 μg/L, respectively, while in the other wines the bound and free MeSA was below 363 μg/L and 12 μg/L, respectively. As this compound’s olfactory threshold is between 50 and 100 μg/L, our data support the hypothesis that methyl salicylate can contribute to the balsamic scent, especially in old Verdicchio wines.

Highlights

Glycosides are plant secondary metabolites consisting of a non-sugar component called an aglycone, attached to one or more sugars
We found that in the free forms the concentration of methyl salicylate (MeSA) in Trebbiano di Soave/Lugana and Verdicchio varieties was in the range 5.5–143 μg/L, while the sum of the 6 glycoside precursors varied from 456–9796 μg/L (Table 2), and in “other” white wines, the free form of MeSA was less than 12 μg/L and lower than 400 μg/L as the sum of 6 glycosides
This study proved the presence of MeSA in bound form in superior concentration as a distinctive characteristic of Verdicchio, Trebbiano di Soave and Trebbiano di Lugana wines

Summary

Introduction

Glycosides are plant secondary metabolites consisting of a non-sugar component called an aglycone, attached to one or more sugars. The aglycone can be an aliphatic alcohol (C6 compounds), a shikimate derivate (benzyl alcohol, phenols, or methyl salicylate) or terpenoid (monoterpenoid or norisoprenoid). All of these compounds can be a reserve of odor compounds after hydrolysis [4]. While the glycosides of terpenes and norisoprenoids present in wine have been the subject of many studies [5,6], those of shikimate derivate are less considered. These are important especially for neutral varieties, since they have been shown to significantly contribute to the dry aromas of figs, tobacco, and chocolate in some wines [7]

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