Metabolite profiling and quantification of phenolic compounds in methanol extracts of tomato fruit

The consumption of tomatoes and tomato products has been associated with a reduction in the risk of contracting some types of cancer and other chronic diseases. These beneficial properties may be attributed to the presence of key metabolites and the interactions among them. We have developed and validated an analytical method for the comprehensive profiling of semi-polar metabolites in the methanol extract of three cultivars of raw tomatoes (Daniela, Raf and Rambo) grown in Almería, in south-east Spain. Diode-array and time-of-flight/ion-trap mass spectrometry detectors were used to ensure the wide detection of metabolites with highly divergent properties. The masses thus detected were assigned by matching their accurate mass-signals with tomato compounds reported in the literature, and supplemented by UV and MS/MS information, reference compounds and existing metabolite databases. In this way we were able to identify tentatively 135 compounds belonging to various structural classes, 21 of which are to our knowledge reported for the first time in the tomato fruit. Among the metabolites identified, the most abundant were phenolic compounds. This class of secondary metabolites is attracting considerable attention from producers and consumers due to their antioxidant activity and nutritional properties. Their quantitative analysis was achieved by using closely related derivatives for each family.