From tyrosine to hydroxytyrosol: a pathway involving biologically active compounds and their determination in wines by ultra performance liquid chromatography with mass spectrometry

Abstract

Background: Hydroxytyrosol (HT) is a bioactive compound present in a limited number of foods such as wines, olives, and olive oils. During alcoholic fermentation, yeast converts aromatic amino acids into higher alcohols such as tyrosol, which can undergo hydroxylation into HT. The aim of this study was to validate an analytical method using ultra performance liquid chromatography coupled with mass spectrometry (UPLC/MS-MS) to quantify HT and its precursors (tyrosine, hydroxyphenylpyruvic acid, hydroxyphenylacetaldehyde, 4-hydroxyphenylacetic acid, and tyrosol) in wines. Their occurrence was evaluated in a total of 108 commercial Spanish wine samples. Results: The validated method simultaneously determined both HT and its precursors, with adequate limits of detection between 0.065 and 21.86 ng mL−1 and quantification limits between 0.199 and 66.27 ng mL−1 in a 5 min run. The concentration of HT in red wines was significantly higher (0.12–2.24 mg L−1) than in white wines (0.01–1.27 mg L−1). The higher the alcoholic degree, the higher was the content of HT. The bioactive 4-hydroxyphenylacetic acid was identified in Spanish wines for the first time at 3.90–127.47 mg L−1, being present in all the samples. Conclusion: The highest HT concentrations were found in red wines and in wines with higher ethanol content. These data are useful for a further estimation of the intake of these bioactive compounds and to enlarge knowledge on chemical composition of wines.