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Table 1. Molar conversion yields of glutathionylated precursors into corresponding thiolsunder enological conditionsPrecursor* not calculatedSpiking (µg/L)Molar conversion yields (%)Synthetic mediumSauvignon Blanc12 4.4G3MH15 0.675 0.6150 0.6G4MMP 1.8 nc* 0.3The direct synthesis of 2-d 10 , adapted from a published protocol [6], was inexpensive andeffective (yield close to 80%). This established protocol was optimized and it can be easilycarried out by non-specialists.To investigate potential relationship between glutathione conjugates and varietalthiols, a synthetic and a Sauvignon Blanc must were spiked with 1-d 2 at severalconcentrations and with 2-d 10 at 1.8 µg/L (Table 1). Fermentation processes wereconducted at laboratory scale with VIN13 (10g/hL) as yeast strain at 20°C. At the end offermentation, synthetic and Sauvignon Blanc wines were extracted and analyzed accordingto well optimized and published methods [8-9] by GC-MS and GC-MS/MS.In the first experiment, the formal identification of 3MH-d 2 in both synthetic andSauvignon Blanc wines (same retention time and similar spectral data such as the referencecompound) proved the direct relationship between 1 and 3MH under enological conditions.The molar conversion yield of 1-d 2 into 3MH-d 2 was lower under synthetic than naturalconditions as already reported for the cysteinylated precursor of 3MH [10] (Table 1). Theconversion of 1-d 2 into 3MH d 2 did not depend on the initial concentration of precursor inmust.In the second experiment, the identification of 4MMP-d 10 in synthetic and naturalwines demonstrated the relationship between 2 and 4MMP under enological conditions.Standard additions of 4MMP d 10 were performed in Sauvignon Blanc wine in order toestimate the molar conversion yield: 0.3% (Table 1). Both S-glutathione conjugates 1 and 2represent the second major precursors of 3MH and 4MMP respectively and opened avenuefor additional studies on varietal thiols biogenesis in wine.AcknowledgmentsWe thank Interloire, Institut Français de la Vigne et du Vin and Sicavac for technical and financialsupport. Supported by CIFRE fellowship (Interloire, Interprofession des vins du Val de Loire).References1. Fedrizzi, B., et al. J. Agric. Food Chem. 57, 991-995 (2009).2. Peyrot des Gachons, C., Tominaga, T., Dubourdieu, D. J. Agric. Food Chem. 50, 4076-4079 (2002).3. Tominaga, T., Furrer, A., Henry, R., Dubourdieu, D. Flavor Fragrance J. 13, 159-162 (1998).4. Darriet, et al. Flavor Fragrance J. 10, 385-392 (1995).5. Roland, et al. Food Chem. 121, 847-855 (2010).6. Grant-Preece, et al. J. Agric. Food Chem. 58, 1383-1389 (2010).7. Roland, et al. J. Agric. Food Chem. accepted for publication (2010).8. Schneider, et al. J. Agric. Food Chem. 51, 3243-3248 (2003).9. Rodriguez-Bencomo, J.J., Schneider, R., Lepoutre, J.P., Rigou, P. J. Chromatogr. A. 1216, 5640-5646 (2009).10. Subileau, M., Schneider, R., Salmon, J.M., Degryse, E. J. Agric. Food Chem. 56, 9230-9235(2008).49