A methyl salicylate glycoside mapping of monovarietal Italian white wines

Among the main plant secondary metabolites, glycosides have a key-role in wine chemistry. Glycosides are non-volatile complexcomposed of a non-sugar component (aglycone) bound to one or more carbohydrates. The hydrolysis of glycosides occurs mainlyduring the fermentation due to the enzymatic activity, and during the storage as a consequence of pH and temperature conditions. Inthe last scenario, the gradual release of aglycones contributes to the aroma evolution of wine. Methyl salicylate (MeSa) is a plantmetabolite known to be a chemical marker of several cryptogamic diseases ; however, it can be also found in wines produced fromhealthy grapes, whose presence provides a pleasant wintergreen and balsamic nuance, especially in aged wines . This volatile odor-active ester can be found, mainly bound to glycosides, into the skin and the stem of the grapes. MeSa in the free form is frequentlypresent under the sensory threshold while in some red and white varieties it can exceed the olfactory threshold. In our previous works MeSa have been found in relevant content, both in bound andfree form, in some genetically related Italian varieties such as Trebbiano di Lugana, Trebbiano di Soave (both employed in theproduction of Lugana wines), and Verdicchio. In this research a straightforward fi lter-and-shot LC-MS/MS method was used for thedetermination of 7 diff erent MeSa glycosides in 246 samples representative of 18 diff erent monovarietal Italian white wines. Thanks tothe minimized sample preparation procedure (wines were only fi ltered at 0.45 μm) this method allowed a reliable quantifi cation of the analyteswithout wasting time, energy, and solvents, in total agreement with the Green Analytical Chemistry principles. Analysis wereperformed using an AB Sciex QTrap 6500+ both in positive and negative mode, equipped with a Waters Acquity C18 HSS-T3 150 mm x2.1 mm x 1.8 μm column working at 0.28 mL*min-1. Glycosides of interest were MeSa 2-O-β-D-glucoside, MeSa 2-O-α-L-arabinopyranosyl(1à6)-β-D glucopyranoside, MeSa 2-O-β-D-xylopyranosyl(1à6)-β-D-glucopyranoside, MeSa 2-O-β-D-apiofuranosyl(1à6)-β-D-glucopyranoside, MeSa 2-O-α-L-rhamnopyranosyl(1à6)-β-D-glucopyranoside, MeSa 2-O-β-D-glucopyranosyl(1à6)-β-D-glucopyranoside, and MeSa 2-O-β-D-xylnopyranosyl(1à2)[O-β-D-xylopyranosyl(1à6)]-O-β-D-glucopyranoside. MeSa glycosides were found in Verdicchio and Lugana wines, in accordance withliterature2,3, whereas where found for the fi rst time in Garganega and Erbaluce varieties. The knowledge of the concentration of MeSaglycosides could be considered a potential predictor of the potential balsamic evolution of white wines. Further details are currentlyunder investigation.