Presence of virgin olive oil phenolic metabolites in human low density lipoprotein fraction: determination by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry.

The biological benefits of olive oil in preventing the oxidation of low density lipoprotein (LDL) would seem to be linked to its high monounsaturated fatty acid contents, but also to its respective phenolic compounds contents. One prerequisite to assess the in vivo physiological significance of phenolic compounds is to determine their presence in human LDL following the ingestion of virgin olive oil. In this work, olive oil phenolic metabolites were identified using high-performance liquid chromatography in tandem with electrospray mass spectrometry (HPLC-ESI-MS/MS) detection, after solid phase extraction (SPE). Quantitative methods were developed in carrying out linearity, precision, sensitivity and recovery tests. The results from two methods of LDL separation were compared and shorter LDL isolation procedure showed a better recovery for antioxidants compounds in LDL. The metabolites identified in LDL were: hydroxytyrosol monoglucuronide, hydroxytyrosol monosulfate, tyrosol glucuronide, tyrosol sulfate and homovanillic acid sulfate. The fact that olive oil phenolic metabolites are able to bind LDL strengthens claims that these compounds act as in vivo antioxidants.