Optimisation and validation of analytical methods for the simultaneous extraction of antioxidants: Application to the analysis of tomato sauces

In the present study, simultaneous extraction of natural antioxidants (phenols and carotenoids) in complex matrices, such as tomato sauces, is presented. The tomato sauce antioxidant compounds studied were the phenolics hydroxytyrosol, from virgin olive oil, quercetin and its derivatives, from onions, and quercetin-rutinoside as well as the carotenoid, lycopene (cis and trans), from tomatoes. These antioxidant compounds were extracted simultaneously with n-hexane/acetone/ethanol (50/25/25, v/v/v). The phenolics were analysed by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS), and lycopene (cis- and trans-forms) was analysed using high-performance liquid chromatography coupled to a diode array detector (HPLC-DAD). After studying the parameters of these methods, they were applied to the analysis of virgin olive oil, fresh onion, tomato concentrate and tomato powder, and commercial five tomato sauces. Subsequently, the results obtained in our laboratory were compared with those from the Gallina Blanca Star Group laboratory.