The leaves of Echinodorus grandiflorus are used traditionally in Brazil for their diuretic and antirheumatic activities. In order to obtain more information about its phenolic constituents, an ethanol leaf extract was fractionated. Five glucosylflavones, five hydroxycinnamoyltartaric acids and trans-aconitic acid were isolated and their structures identified by NMR data and chiral HPLC. Quantitative determination of compounds 1 - 11 by HPLC indicated caffeoylferuloyltartaric acid with 0.13% as the main representative of the hydroxycinnamoyltartaric acids and swertiajaponin with 0.31% of the glucosylflavones; the content of trans-aconitic acid in the investigated material was 0.98%.