Taste-Guided Isolation of Bitter Lignans from Quercus petraea and Their Identification in Wine

Abstract

Quercoresinosides A and B (1 and 2), two new lignans, were isolated from a toasted Quercus petraea heartwood extract along with a known compound, 3-methoxy-4-hydroxyphenol 1-O-β-d-(6'-O-galloyl)glucopyranoside (3). The purification protocol was based on a taste-guided approach that sought to reveal new bitter compounds released from oak wood into wines and spirits. HRMS and NMR data were used to establish that compounds 1 and 2 are lignan derivatives bearing a glucosyl unit and a galloyl unit at the same positions. Hydrolysis of these compounds showed that they could be distinguished by the absolute configuration of their respective lyoniresinol genin as determined by chiral LC-HRMS in comparison with (+)- and (-)-lyoniresinol standards. Sensory analyses were performed in a non-oaked wine on the pure compounds 1-3. The three molecules exhibited a bitter taste at 2 mg/L that was particularly intense for compounds 2 and 3. Finally, LC-HRMS demonstrated the occurrence of compounds 1-3 in oaked wine and brandy, which supports the hypothesis of their contributions to the increase in bitterness during oak aging.

Phenolic Composition and Related Properties of Aged Wine Spirits: Influence of Barrel Characteristics. A Review

“…Baldwin et al [13] found low levels of vanillin (ranging from 0.6 to 1. The most recent works [6,56,105] were based on a factorial design using the same wine distillate from the Lourinhã region (produced by Adega Cooperativa da Lourinhã) aged over a four-year period in barrels made from the following kinds of wood: Limousin oak (Q. robur L.) and Allier oak (Q. sessiliflora Salisb.) from French forests; American oak (mixture of Q. alba L./Q.…”

“…Portuguese oak wood promoted intermediate enrichment, with the highest level of sinapaldehyde, while the other kinds of oak had a weaker performance. However, the richness of coumarins associated with the American oak should be stressed, because these compounds can act as chemical markers of this kind of wood [56,95]. Comparing the results of the oldest and most recent works, important differences in the concentrations of phenolic aldehydes, phenolic acids and scopoletin in wine brandies aged in French oak wood and American oak wood are observed.…”

“…In recent years, a comprehensive investigation was performed [6,56,120]. In that study, the same wine distillate from Lourinhã region (produced by Adega Cooperativa da Lourinhã) was aged over a four-year period in 250 L barrels.…”

“…Analysing the low molecular weight phenolic compounds of the wine spirits aged in them, Canas [56] showed that the toasting level had a significant effect on the concentration of all phenolic compounds, except for scopoletin (Table 5), confirming the results of previous studies [96,97,164,165]. Concentration in mg/L absolute ethanol except for coumarins, which are in µg/L absolute ethanol; mean values (n = 56) followed by different letters ( a , b , c ) in a row are significantly different (p < 0.05); ΣLMW-Sum of low molecular weight phenolic compounds concentrations.…”

“…There is evidence on the relationship between: the vanilla aroma and vanillin concentration [24,49,50]; the bitterness and phenolic acids, their ethyl esters, and (+)-lyoniresinol concentrations [48,[51][52][53][54]. Among these properties, the vanilla aroma should be highlighted due to its outstanding importance for aged wine spirit quality [55][56][57]. The relationship between astringency and ellagitannin and gallotannin concentrations is still unclear for thesekind of beverages [48,[51][52][53][54]58,59].…”