Evaluation of Eugenia uniflora L. leaf extracts obtained by pressurized liquid extraction: Identification of chemical composition, antioxidant, antibacterial, and allelopathic activity

Pitangueira (Eugenia uniflora L.) leaves are rich in phenolic compounds. To evaluate these compounds, pitangueira leaves were submitted to extraction by aqueous infusion (AI) and by pressurized liquid extraction (PLE). PLE extracts were obtained with water (PLE-W), water:ethanol (PLEW:E), and ethanol (PLE-E). Fifty-four extracted compounds were tentatively identified by LC-MS. The PLE-W:E extraction resulted in a higher concentration of phenolic acids and tannin compounds, while PLE-E showed a higher concentration of flavonoids. All extracts tested in vitro showed good antioxidant activity, as evaluated by thiobarbituric acid reactive substances (TBARS) and reactive oxygen species (ROS) assays in rat brain homogenates model systems and in protecting yeasts under oxidation. Among the eight bacterial strains tested with the pitangueira leaf extracts, antibacterial activity was observed mainly against Staphylococcus aureus with the extracts of AI, PLE-W, and PLE-W:E. And for Pseudomonas aeruginosa, only the AI extract showed antibacterial activity. The other strains were not affected by the extracts. All extracts exhibit an allelopathic effect against lettuce seeds. Even though 72.2% of the putatively identified compounds were common to all extracts, PLE extracts provide more regular antioxidant, antibacterial, and allelopathic activities.