Antimicrobial activities of extracts from Urtica urens

The antibacterial and antifungal activities of various extracts from Urtica urens were evaluated against selected microorganisms using agar hole-plate diffusion method. A total of ten extracts namely U. urens hexane leaf extract (HLE), chloroform leaf extract (CLE), ethyl acetate leaf extract (ELE), methanolic leaf extract (MLE), hexane stem-bark extract (HSB), chloroform stem-bark extract (CSB), ethyl acetate stem-bark extract (ESB), methanolic stem-bark extract (MSB), chloroform root extract (CRT) and methanolic root extract (MRT) were prepared. These extracts were evaluated against two Gram-positive bacteria viz. Listeria monocytogenes and Staphylococcus aureus, four Gram-negative bacteria viz. Serratia marcescens, Pseudomonas aeruginosa, Escherichia coli (wild strain) and Escherichia coli (O157:H7) and two fungal isolates viz. Candida albicans and Penicillium digitatum. The inhibition zones of these extracts were found to be in the range of 9.0±0.0 to 40.5±0.7 mm against bacterial isolates and 16.0±4.2 to 17.5±4.9 mm against C. albicans. However, all these extracts exhibited no visible zone of inhibition against P. digitatum. Additionally, the minimum inhibitory concentrations (MICs) of these extracts were also determined and were found to be in the range of <31.25 to >1000 µg/mL against both bacterial and fungal isolates. From this study, we concluded that ELS, MLE, CRT and MRT showed promising antimicrobial activities.