Table olive polyphenols: A simultaneous determination by liquid chromatography-mass spectrometry

Table olives contain a wide range of polyphenols responsible for protective effects on health that have been associated with a lower prevalence of chronic diseases. A new method to identify and quantify these compounds in table olives, by means of methanol:ethanol (1:1; v/v) extraction followed by LC-ESI-MS/MS, has been developed and validated. The chromatographic column Eclipse-XDB-C18, never used before in this kind of application, provided the best results using Milli-Q water with 0.025% acetic acid and acetonitrile with 5% acetone as eluents. This method allows the quantification of 17 polyphenols, namely, hydroxytyrosol, tyrosol, salidroside, hydroxytyrosol acetate, catechol, vanillic acid, caffeic acid, o-coumaric acid, p-coumaric acid, verbascoside; oleuropein; pinoresinol, apigenin, luteolin, luteolin-7-O-glucoside, quercetin and rutin. The new method has been validated and shows linear correlations (R²>0.996), recoveries superior to 95%, high sensitivity, adequate precision and accuracy (RSD < 15%) as well as a short chromatographic analysis of 9 min. Its application to the analysis of Marfil table olives enabled the quantification of 15 polyphenols, among which hydroxytyrosol (384.1 ± 81.2 mg/kg), tyrosol (201.2 ± 3.8 mg/kg), luteolin (88.0 ± 3.8 mg/kg) and salidroside (85.9 ± 3.2 mg/kg) stand out. Furthermore, this method allows to assess whether the intake of a certain number of olives can meet the health claim associated to olive oil polyphenols (Reg. EU n.432/2012). Our results indicate that the daily intake of only 7 olives, which corresponds to 8 g of edible portion, provide an amount of hydroxytyrosol and derivatives (e.g. oleuropein complex and tyrosol) of 5 mg, according to the health claim of the EU. In view of the results, it could be stated that table olives are an excellent source of bioactive compounds, thus emerging as a promising functional food.