Total Synthesis and Analysis of Phenolic Phytoprostanes, Oxidized Derivatives of Lipophenols

Lipophenols, or phenolipids, are compounds that combine polyphenols with fatty acids, offering the antioxidant properties of polyphenols alongside the neuroprotective and cardioprotective benefits of omega-3 polyunsaturated fatty acids (PUFAs). Hydroxytyrosol (HT)-based lipophenols have recently been identified in olive oil. Depending on their structure, these compounds were differently affected by storage conditions. While the concentrations of HT-oleate and HT-linoleate increase with higher storage temperatures, HT-α-linolenate (HT-ALA) did not follow the same trend. Given the high oxidative susceptibility of α-linolenic acid (ALA), which leads to oxidation products known as phytoprostanes (PhytoPs), we hypothesize that HT-ALA may be oxidized into covalently bound PhytoP conjugates of HT (PhytoPs-HT) under various oxidative conditions, including, for example, suboptimal storage. This study aims to develop the first total synthesis of two series of PhytoPs-HT as analytical standards to explore the oxidative transformation of HT-ALA lipophenols into potential oxylipin metabolites. The synthesis of four ALA-derived PhytoPs-HT and their identification during in vitro oxidation of HT-ALA by UHPLC-HRMS/MS are presented here. These synthetic standards are essential for the reliable identification and quantification of HT-PhytoPs within complex mixtures of regio- and stereoisomers generated during oxylipin formation.