Sulfated phenolic acids in plants

Main conclusion Sulfated phenolic acids are widely occurring metabolites in plants, including fruits, vegetables and crops. Abstract The untargeted UHPLC-QTOF-MS metabolomics of more than 50 samples from plant, fungi and algae lead to the discovery of a small group of sulfated metabolites derived from phenolic acids. These compounds were detected in land plants for the first time. In this study, zosteric acid, 4-(sulfooxy)benzoic acid, 4-(sulfoooxy)phenylacetic acid, ferulic acid 4-sulfate and/or vanillic acid 4-sulfate were detected in a number of edible species/products, including oat ( Avena sativa L.), wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.), tomato ( Solanum lycopersicum L.), carrot ( Daucus carota subsp. Sativus Hoffm.), broccoli ( Brassica oleracea var. Italica Plenck), celery ( Apium graveolens L.), cabbage ( Brassica oleracea convar. sabauda L.), banana tree ( Musa tropicana L.), pineapple fruit ( Ananas comosus L.), radish bulb ( Raphanus sativus L.) and olive oil ( Olea europaea L.). The structural identification of sulfated compounds was performed by comparing retention times and mass spectral data to those of synthesized standards. In addition to above-mentioned compounds, isoferulic acid 3-sulfate and caffeic acid 4-sulfate were putatively identified in celery bulb ( Apium graveolens L.) and broccoli floret ( Brassica oleracea var. Italica Plenck), respectively. While sulfated phenolic acids were quantified in concentrations ranging from 0.34 to 22.18 µg·g −1 DW, the corresponding non-sulfated acids were mostly undetected or present at lower concentrations. The subsequent analysis of oat symplast and apoplast showed that they are predominantly accumulated in the symplast (> 70%) where they are supposed to be biosynthesized by sulfotransferases.