Disclosure of the nature of glycosylated varietal precursors of eugenol from the hybrid, tolerant grapevine variety Baco blanc: Methodology and quantification.

A varietal origin of eugenol was previously demonstrated in Baco blanc, a major grapevine variety used to produce Armagnac wine spirits. Eugenol was found in high amount, both as the free and as unidentified glycosylated forms. To reveal their identity, a specific method was developed and applied to berry skin extracts. This EPIQ (Extraction-Purification-Identification-Quantification) procedure comprised HS-SPME GC-MS-guided LC fractionation, combined with specific enzymatic hydrolyses as well as LC-MS/MS and LC-HRMS analyses. Comparison with commercial standards allowed for the identification of geoside (eugenyl-6-O-α-L-arabinopyranosyl-b-D-glucopyranoside) as a major eugenol precursor. This is the first study to find geoside in grapevine. Three minor eugenol precursors were also putatively determined, including the monoglucoside, citrusin C. Two other diglycosides of eugenol were also hypothesised. LC-MS/MS quantifications confirmed presence of a larger amount of geoside in Baco blanc than in Vitis vinifera grapes. Geoside reach a maximum concentration in berry skins of Baco blanc at veraison.