LC-MS/MS quantitation of polyphenols and secoiridoids in edible olives

Abstract

Table olives are a traditional product and a very important component of the Mediterranean diet. Olive fruits are sources of hydroxytyrosol, oleuropein and many other biophenols or secoiridoid derivatives. The chemical consistency of the final olive products is influenced by the olive variety and the debittering method. Our study was focused on the impact of California style and the dry salt processing on the concentration of hydroxytyrosol (HT), oleuropein (OLE), hydroxytyrosol glucosides, saligstroside, luteolin glucosides, rutin, verbascoside, oleoside methyl ester, 2,6-dimethoxy-p-benzoquinone, phenolic acids (caffeic acid, chlorogenic acid, coumaric acid), oleuropein (OLE-A) and ligstroside aglycons. A rapid method for the extraction and quantitation by LC-MS/MS of the above described products in olive fruits was developed. The method was first applied in California style processed Manzanilla olives. The initial values of OLE was 7.4mg/g wet flesh, for OLE-A 3.7mg/g wet flesh and for HT 0.72mg/g wet flesh. At the end of the debittering process only HT, OLE and OLE-A could be detected in levels ranging between 130–165µg/g. All the other compounds presented concentration lower than 50µg/g and 7 of them could not be detected. In contrast the Mission and Throuba Thassos olives processed by the dry salt method presented high amounts of almost all studied compounds especially OLE, HT, OLE-A and hydroxytyrosol glucosides (ranging from 312 to 1720µg/g). In conclusion, the variety and processing style has a strong impact on the majority of the main olive bioactive compounds.