Untargeted screening of the bound / free phenolic composition in tomato cultivars for industrial transformation

Tomato is one of the most important agricultural crops and it is characterized by a wide bioactive compound profile. However, little information is reported on its comprehensive polyphenol profile. In this work, 13 commercial tomato cultivars for industrial transformation were screened by ultra-high-pressure liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UHPLC-QTOF-MS) for both free and bound phenolic profiles. Thereafter, the in vitro antioxidant activity of each cultivar was assessed by ferric reducing antioxidant power (FRAP) and oxygen radical absorbance activity (ORAC) assays. Multivariate statistics, i.e. orthogonal projection to latent structures discriminant analysis (OPLS-DA), were then used to model samples according to their distinct phenolic signatures, thus providing compounds that better discriminated between the distributions of the cultivars that were considered. RESULTS: More than 350 phenolic compounds could be identified across the samples that were considered: flavonoids (such as flavones and flavanols), hydroxycinnamic acids, lignans, and lower-molecular-weight phenolics were the most frequently observed classes of phenolics in tomato berries. Anthocyanins were the most abundant class among bound phenolics (being highest in the Leader F1 and Defender F1 cultivars), followed by tyrosols (mainly in Heinz cultivars). However, flavones and hydroxybenzoic acids were the most represented discriminant phenolics in the bound fraction. CONCLUSIONS: Untargeted metabolomics allowed significant differences in phenolic composition to be outlined across the tomato cultivars that were analyzed. Such differences were particularly evident regarding the free-to-bound phenolic ratio, hence allowing differences in the bioaccessibility of phenolics to be postulated.