Prediction of retention time for plant food compounds & metabolites in a multi-laboratory initiative

Plant food bioactives (flavonoids, phenolic acids, lignans, carotenoids, monoterpenes, glucosinolates, alkaloids…) receive widespread interest for their protective health effects. However, their identification in untargeted metabolomic profiles of food, biofluids and tissues remains a challenging feat. Plant food bioactives and their Phase I, -II and gut microbial metabolites cover a large chemical space ranging from highly polar to lipophilic compounds and including aglycones, glycosides, and conjugated metabolites. Spectral libraries are incomplete for these compounds and standards are often costly or not commercially available. In addition to mass fragmentation data, retention time (RT) is a valuable information for assisting the identification of unknowns, as it helps to narrow the number of hypotheses within an observed RT window to a manageable number of compounds. In the framework of the COST Action POSITIVe (https://www6.inra.fr/cost-positive, FA1403), we evaluated the usefulness of PredRet (http://predret.org), an open access RT database, to predict RT of plant food bioactive metabolites in a multi-laboratory test involving 19 laboratories across Europe, using 24 reversed-phase LC-MS or LC-PDA Chromatographic Systems (CS=column + elution phases and gradient). PredRet is a community-driven database of compound RTs that is free to use to predict in your own CS the RT of compounds that have been experimentally measured in other CS.