Bioassay‑guided In vitro Study of the Antimicrobial and Cytotoxic Properties of the Leaves from Excoecaria Lucida Sw

Background: Excoecaria lucida Sw. (Euphorbiaceae) is a plant conventionally used throughout the Caribbean in the treatment of infectious diseases. Objective: To evaluate, using bioassay‑guided fractionation, the in vitro cytotoxicity and antimicrobial activity of E. lucida leaves. Materials and Methods: A 95% ethanol crude extract was dried and fractionated by solid‑liquid separation in four phases (hexane, dichloromethane, ethyl acetate, and butanol). Antimicrobial activity (3 bacteria, 6 yeasts, and 2 fungi) was evaluated by the dilution method with resazurin (2048, 512, 128, 32, and 8 µg/mL). The cytotoxicity assays were evaluated in two cell lines: MRC‑5 and RAW 264.7; calculating the selectivity index. Assays were performed for the total extract, the isolated compound with the highest yield, and the ethyl acetate and butanol phases. Isolated compounds were characterized by nuclear magnetic resonance and mass spectrometry techniques. Results: Fractionation process led to the isolation of ellagic acid (784.29 mg), 3,3’,4’‑tri‑O‑methyl ellagic 4‑O‑β‑D‑glucopyranoside acid (6.1 mg), and corilagin (6.91 mg). The most active were ethyl acetate phase and ellagic acid with IC₅₀ = 128 μg/mL against seven and five different species of microorganisms, respectively. The total extract (IC₅₀ = 512 µg/mL) and the ethyl acetate phase (IC₅₀ = 128 µg/mL) were cytotoxic in both cell lines, while butanol phase and ellagic acid both with IC₅₀ >2048 µg/mL seemed to be safer. Conclusions: The results obtained indicate that the Excoecaria leaves can be conventionally used as antimicrobial, but it should be present that some cytotoxicity could appear. In addition, the three identified compounds were reported for the first time in the species.