Journal of Medicinal Plants Research Vol. 6(38), pp. 5166-5172, 3 October, 2012 Available online at http://www.academicjournals.org/JMPR DOI: 10.5897/JMPR12.482 ISSN 1996-0875 ©2012 Academic Journals Full Length Research Paper Antibacterial activity of extracts of diploid and induced autotetraploid Tunisian populations of Trigonella foenum-graecum L. Nidhal Marzougui 1 *, Anissa Boubaya 1 , Ines Thabti 1 , Ali Ferchichi 1 and Amina Bakhrouf 2 1 Laboratory of Dry Land Farming and Oasis Cropping, Institut des Regions Arides, Médenine, Tunisia. 2 Laboratory of Analysis, Treatment and Recovery of Environmental Pollutants and Products, Faculty of Pharmacy, Department of Microbiology, Avicenne Street, 5000 Monastir, Tunisia. Accepted 12 April, 2012 Trigonella foenum-graecum L. is a medicinal plant known for its various pharmacological properties, including the anti-bacterial and the anti-microbial effects. This study aimed to determine and compare the antibacterial activities of extracts of two Tunisian T. foenum-greacum populations, diploid (2n=16) and its induced autotetraploid (4n=32). Aqueous and organic extracts (petroleum ether, ethyl acetate and methanolic fractions) prepared from seeds and leaves were assayed to determine their antibacterial potential against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli and Salmonella Typhimurium using agar disk diffusion method. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined. The results showed that the organic extracts had no antibacterial potential against the tested bacteria contrary to the aqueous extracts. The extracts prepared from the seeds were more active compared to those prepared from the leaves against all tested strains. And the induced autotetraploid population presented an antibacterial activity higher than that of the diploid population. Key words: Trigonella foenum-graecum, diploid, autotetraploid, antibacterial activity, aqueous extracts, organic extracts, seeds, leaves. INTRODUCTION The appearance of resistant pathogens paved the way to the occurrence of infections that are only treated by a limited number of antimicrobial agents. Bacterial resistance to antimicrobial agents is a medical problem with public health and socio-economic implications. The change in the resistance patterns will continue to menace the developed and developing countries (Abdou et al., 2011). The world is nowadays witnessing an emergence of several multi-drug resistant organisms rendering the treatment options more and more limited. The emergence of resistant Gram negative (Abdel-Massih et al., 2010) and Gram positive bacteria (Akins et al., 2005) presents a major challenge for the antimicrobial therapy and *Corresponding author. Email: marzouguinidhal@gmail.com. significantly narrows the treatment options of human infections. In view of the negligible development of anti- biotics in the past few years, there is an urgent need for new antibacterial compounds in order to fight the emer- gence of these new resistant pathogens. For centuries, plants have been used as remedies and treatments of diseases. The Mediterranean region is rich in plant species many of which are considered to have medicinal effects. However, there is relatively limited research on medicinal plants in this region (Saad et al., 2005). Trigonella foenum-graecum L., or fenugreek, is one of the oldest medicinal plants, found in nature and cultivated in North Africa, the Middle East and India (Petropolous, 2002). It is an annual herb of Fabaceae which is used as human food and forage. Their seeds are described in the Greek and Latin Pharmacopoeias for their various pharmacological properties, including the