Antibacterial Activity of Ethanolic and Aqueous Leaf Extracts of Datura Against Escherichia coli and Staphylococcus aureus Using the Microtiter Plate Method
TL;DR
Datura leaf extracts show moderate, concentration- and time-dependent growth-inhibitory activity (measured by optical density), with a stronger effect on the Gram-negative test organism; bactericidal activity was not assessed.
Abstract
Background: The increasing resistance of pathogenic bacteria to conventional antibiotics has renewed interest in medicinal plants as sources of new antimicrobial agents. Datura (Solanaceae) is widely used in traditional medicine and is rich in tropane alkaloids and other secondary metabolites. Objective: This study evaluated the antibacterial activity of ethanolic and aqueous leaf extracts of Datura, collected in Misurata, Libya, against a Gram-negative bacterium (Escherichia coli) and a Gram-positive bacterium (Staphylococcus aureus). Methods: Leaves were examined microscopically to document their diagnostic features. Extracts were prepared by maceration with 75% ethanol or distilled water for 48 h at 35–45 °C with magnetic stirring. Each extract was tested at 20%, 40% and 60% concentration using the 96-well microtiter plate method; optical density was read at 630 nm after 12 h and 24 h of incubation at 37 °C, and the percentage of growth inhibition was calculated against growth controls. Results: Microscopy revealed anomocytic stomata, glandular and covering trichomes, lignified vessels and calcium oxalate crystals. Both extracts inhibited bacterial growth to different degrees. The ethanolic extract inhibited E. coli by 24.7–43.0% (maximum 42.98% at 60%, 12 h) and S. aureus by 7.7–19.5% (maximum 19.51% at 60%, 12 h). The aqueous extract inhibited E. coli by 18.1–39.6% (maximum 39.56% at 40%, 12 h) and S. aureus by 0–12.6% (maximum 12.63% at 40%, 12 h). Inhibition was generally greater at 12 h than at 24 h and was consistently higher against E. coli than against S. aureus. Conclusion: Datura leaf extracts show moderate, concentration- and time-dependent growth-inhibitory activity (measured by optical density), with a stronger effect on the Gram-negative test organism; bactericidal activity was not assessed. Further phytochemical characterization and determination of minimum inhibitory concentrations are recommended.