Full Length Research Paper

Abstract

The chemical composition of essential oils (EO) isolated from four Nepeta species (Nepeta atlantica Ball, Nepeta tuberosa L. subsp reticulata (Desf.) Maire, Nepeta cataria L., Nepeta granatensis Boiss) were characterized and the antibacterial activity tested. Chemical analyses indicated that the major component of these EO was the sterioisomere 4a-, 7-, 7a--nepetalactone which represented more than 70% of oils from N. atlantica, N. tuberosa, N. cataria and 39.4% of oils from N. granatensis. The EO from N. atlantica, N. tuberosa, and N. cataria presented comparable antibacterial activity against tested bacteria. Statistical analysis indicated that S. aureus (ATCC 25923) and E. coli (ATCC 25922) strains were the most sensitive to the EO (MICs ranged from 4.37 to 16.25 µL/mL), these strains were more sensitive than clinically isolated E. coli, S. aureus and S. enteritidis and P. aeruginosa (ATCC 27853) strains. The EO from N. granatensis contained low nepetalactone concentrations and showed relatively poor antibacterial activity against tested bacteria (MICs ranged from 22.50 to 80.00 µL/mL). These results indicate that the antibacterial activity of EO from the Nepeta genus depends on their chemical composition and suggests that nepetalactone plays an important role in antibacterial activity against E. coli and S. aureus strains, two microorganisms which cause morbidity and mortality worldwide.

Key words: Nepeta atlantica, Nepeta tuberosa, Nepeta granatensis, Nepeta cataria , Lamiaceae, essential oil  composition, 4a-, 7-,7a--nepetalactone, antibacterial activity.