A COMPARATIVE STUDY OF THE ANTIBACTERIAL ACTIVITY OF URTICA DIOICA L. AND URTICA DIOICAL. VARIETY ANGUSTIFOLIA

Urtica dioica L. and Urtica dioica L. angustifolia are commercialized as the same plant under the name stinging nettles (Ortiga) but, to our knowledge, the antibacterial properties of the variety angustifolia are unknown. The antibacterial activity of Urtica dioica L., collected in the State of Mexico, was compared with that of Urtica dioica L. variety angustifolia, acquired in a market in Mexico City. The extracts were obtained by consecutive maceration of leaves in hexane, dichloromethane, methanol, and water for 48 h, dilutions of 5-0.03 mg/mL of each were added to culture plates with 4 x 10⁶ Colony-forming units (CFU)/mL, resazurin, and Müeller-Hinton medium 3X. The cultures were incubated for 22 h/37°C. The bacteria employed were as follows: Salmonella typhimurium, Shigella flexneri, Salmonella typhi, Proteus mirabilis, Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. Each extract was evaluated on three occasions in triplicate. 1% Dimethyl sulfoxide (DMSO) and a solution of Penicillin-Streptomycin were used as negative and positive control, respectively. In terms of Urtica dioica L., the hexanic and dichloromethanic extracts inhibited B. subtilis and S. aureus. The methanolic extract inhibited S. flexneri and S. typhi. Antibacterial activity was observed in seven of the 28 seeded wells. U. dioica L. var. Angustifolia, with 10 wells exhibiting antibacterial activity. The hexanic, dichloromethanic, and methanolic extracts inhibited B. subtilis at 0.25, 1.25, 1.25 mg/mL, respectively. The dichloromethanic, methanolic, and aqueous extracts inhibited S. typhi. Also inhibited S. flexneri. The minimal inhibitory concentration (MIC) was 0.125 mg/Ml with U. dioica L.