High-antibacterial activity of Urtica spp. seed extracts on food and plant pathogenic bacteria

Abstract

The aim of this study was to comparatively evaluate antibacterial activities of methanol (MetOH) and aqueous (dw) leaf (L), root (R) and seed (S) extracts of Urtica dioica L. (Ud; stinging nettle) and Urtica pilulifera L. (Up; Roman nettle) on both food- and plant-borne pathogens, with total phenolic contents and DPPH radical scavenging activities (DRSA). MetOH extracts of leaves and roots of U. dioica had the highest DRSA. Extracts with high antibacterial activity were in the order Up-LMetOH (13/16) > Ud-SMetOH (11/16) > Up-SMetOH (9/16). Results obtained with Up-SMetOH against food spoiling Bacillus pumilus, Shigella spp. and Enterococcus gallinarum with minimum inhibitory concentrations (MICs) in 128–1024 μg/ml range seem to be promising. Up-SMetOH also exerted strong inhibition against Clavibacter michiganensis with a considerably low MIC (32 μg/ml). Ud-SMetOH and Up-LMetOH were also effective against C. michiganensis (MIC = 256 and 1024 μg/ml, respectively). Ud-SMetOH and Ud-RMetOH had also antimicrobial activity against Xanthomonas vesicatoria (MIC = 512 and 1024 μg/ml, respectively). Results presented here demonstrate high-antibacterial activity of U. pilulifera extracts and U. dioica seed extract against phytopathogens for the first time, and provide the most comprehensive data on the antibacterial activity screening of U. pilulifera against food-borne pathogens. Considering limitations in plant disease control, antibacterial activities of these extracts would be of agricultural importance.

Keywords::

• Urtica dioica
• Urtica pilulifera
• food-borne pathogens
• phytopathogens
• free radical scavenging
• phenolic contents

Acknowledgements

Department of Medical Biochemistry, Faculty of Medicine, Baskent University, is greatly thanked for lyophilization process. Phytopathogen strains were generous gift of Prof. Dr Yeşim Aysan.

Declaration of interest : This study was approved by Baskent University Institutional Review Board (Project no: DA10/17), and supported by Baskent University Research Fund. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.