Evaluation of cytotoxic, immunomodulatory and antibacterial activities of aqueous extract from leaves of Conocarpus erectus Linnaeus (Combretaceae).

Objectives: This work evaluated the antibacterial activity, cytotoxicity and immunomodulatory effect on human peripheral blood mononuclear cells (PBMCs) promoted by aqueous extract from Conocarpus erectus leaves (AELCe).
Methods: The extract was characterized by thin layer chromatography and ultraperformance liquid chromatography coupled to mass spectrometry (UPLC-MS). Cytotoxicity of AELCe (6.25-50 μg/ml) was investigated using annexin V and propidium iodide. Cytokine and nitric oxide levels in PBMCs culture supernatants exposed or not to AELCe (12.5 μg/ml) were determined, and antibacterial activity was evaluated by disc diffusion and broth microdilution methods.
Key Findings: AELCe contained 3',4'-OH flavonoids, phenylpropanoglycosides, saponins, polymeric proanthocyanidins and hydrolysable tannins. Moreover, 10 other compounds were identified through UPLC-MS technique. AELCe did not affect lymphocyte viability at 6.25 and 12.5 μg/ml. IL-2, IL-10, TNF-α, IFN-γ and nitric oxide was produced in higher levels by cells treated with AELCe. Proliferation and activation of CD8 ⁺ T lymphocytes were also stimulated. AELCe showed bacteriostatic activity against clinical and antibiotic-resistant strains of Staphylococcus aureus (MIC between 250 and 1000 μg/ml).
Conclusions: AELCe showed a moderate bacteriostatic activity and promoted an immunomodulatory status through higher production of Th1 cytokines, nitric oxide release and T CD8 ⁺ lymphocytes stimulation.
(© 2018 Royal Pharmaceutical Society.)