Quantitative analysis of glycoconjugate precursors of guaiacol in smoke-affected grapes using liquid chromatography–tandem mass spectrometry based stable isotope dilution analysis

Guaiacol has been shown to accumulate in glycoconjugate forms in the fruit and leaves of grapevines following vineyard exposure to bushfire smoke. To investigate the glycosylation of guaiacol in smoke-affected grapes, a quantitative stable isotope dilution analysis method using liquid chromatography-tandem mass spectrometry was developed and validated, using the [2H4]-labelled analogue of guaiacol β-d-glucopyranoside as internal standard. The method was subsequently applied to the analysis of grapes sampled from grapevines exposed to either bushfire or experimental smoke, enabling compositional comparisons of guaiacol glycoconjugates in smoke-affected grapes from different varieties to be determined, for the first time. ol glucose–pentose disaccharide conjugates (i.e. glucosides with a terminal pentose) were found to be the most abundant glycoconjugate precursors present in smoke-affected grapes, regardless of grape variety or smoke source. Higher concentrations of glycoconjugates were measured in extracts of whole berry homogenate than juice.