Marine halophytes are an outstanding reservoir of natural products and several species have anti-infectious traditional uses. However, little is known about their potential against neglected tropical ailments, such as Chagas disease. This work evaluated for the first time the in vitro anti-Trypanosoma cruzi activity of extracts from the aromatic and medicinal species Helichrysum italicum subsp. picardii (Boiss. & Reut.) Franco (Asteraceae, everlasting) and Crithmum maritimum L. (Apiaceae, sea

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... nnel). For that purpose, decoctions, tinctures and essential oils from everlasting's flowers and sea fennel's stems, leaves and flowers were tested against intracellular amastigotes of two T. cruzi strains. Sea fennel's flowers decoction displayed significant anti-trypanosomal activity and no toxicity towards the host cell (EC50 = 17.7 µg/mL, selectivity index > 5.65). This extract was partitioned using liquid-liquid extraction affording 5 fractions that were re-tested in the same model of anti-parasitic activity. Fraction 1 was the most active and selective (EC50 = 0.47 μg/mL, selectivity index = 59.6) and was submitted to preparative thin layer chromatography. The major compound present, likely responsible for the observed anti-trypanosomal activity, was identified as falcarindiol. Target fishing studies showed falcarindiol as a ligand of T. cruzi spermidine synthase, pointing to a potential enzyme-inhibiting anti-trypanosomal mechanism of action.