Helicobacter pylori is a bacterium that reaches half of the world population and it's recognized as the main cause of chronic gastritis and peptic ulcer. In this study, we evaluated the anti-H. pylori, antioxidant and immunomodulatory activities of the methanolic (MeOH) extract of Eugenia uniflora leaves and chemical profile. Anti-H. pylori activity was evaluated by spectrophotometric broth microdilution technique by determining the HIGHLIGHTS • E. uniflora MeOH extract has anti-Helicobacter pylori activity; • E. uniflora showed antioxidant and immunomodulatory effects; • Some tannins and flavonoids identified are reported to biological activity;

Studies estimate that nearly 2 million new cases of gastric cancer will occur worldwide during the next two decades, which will increase mortality associated with cancer and the demand for new treatments. Marine algae of the Laurencia genus have secondary metabolites known for their cytotoxic action, such as terpenes and acetogenins. The species Laurencia obtusa has demonstrated cytotoxicity against many types of tumors in previous analyses. In this study, we determined the structure of terpenes, acetogenins, and one fatty acid of Laurencia using mass spectrometry (ESI-FT-ICR/MS). In vitro cytotoxicity assays were performed with adenocarcinoma gastric cells (AGS) to select the most cytotoxic fraction of the crude extract of L. obtusa. The Hex:AcOEt fraction was the most cytotoxic, with IC50 9.23 µg/mL. The selectivity index of 15.56 shows that the Hex:AcOEt fraction is selective to cancer cells. Compounds obtained from L. obtusa were tested by the analysis of crystallographic complexes. Molecular docking calculations on the active site of the HIF-2α protein showed the highest affinity for sesquiterpene chermesiterpenoid B, identified from HEX:AcOEt fraction, reaching a score of 65.9. The results indicate that L. obtusa presents potential compounds to be used in the treatment of neoplasms, such as gastric adenocarcinoma.