Planta Med 2007; 73 - P_209
DOI: 10.1055/s-2007-986990

Antimicrobial effect of Helichrysum plicatum DC. subsp. plicatum extracts on Escherichia coli O157:H7

M Aslan 1, A Demir 2, B Mercanoglu 2, A Aykac 2, E Yesilada 3
  • 1Gazi University, Faculty of Pharmacy, Department of Pharmocognosy 06330 Etiler-Ankara, Turkey
  • 2Hacettepe University, Faculty of Engineering, Department of Food Engineering Beytepe-Ankara, Turkey
  • 3Yeditepe University, Faculty of Pharmacy, Department of Pharmocognosy İstanbul, Turkey

Members of the genus Helichrysum have been used in folk medicine mainly as anti-microbial, anti-inflammatory, digestive, choleretic and diuretic [1–3]. Escherichia coli O157:H7 was first recognized as a pathogen in 1982 and is considered as the main cause of hemorrhagic colitis. Despite many investigations on the antimicrobial activity of different Helichrysum species, the effect on E. coli O157:H7 has not yet been evaluated in detail. The present study investigates with the antibacterial activity of H. plicatum DC. subsp. plicatum (HPP) against E. coli O157:H7. The extracts used in this study, that were obtained from the ethanol and water extraction of flower and leaf parts of HPP were Flower EtOH (HFE), Leaf EtOH (HLE), Flower Water (HFW) and Leaf Water (HLW) extracts; and the sub-extracts were obtained by successive solvent extractions of HFE by n-hexane (HFEH), chloroform (HFEC), ethyl acetate (HFEEA), n-butanol (HFEB), the remaining aqueous part was designated as HFER. We investigated the effect of plant extracts at different concentrations on the survival of overnight culture of E. coli O157:H7at 37°C for a week. All extracts (except for HFE) did not show any significant activity in this screening test even at a concentration of 2.5%. Although antibacterial activity of 0.5% concentration of HFE against E. coli O157:H7 was less than the activity of the other concentrations, all concentrations of HFE extract had a bacteriostatic or bactericidal effect against E. coli O157:H7 (MIC value 62.5µg/ml). Since HFE was found to be the most effective extract of the plant, the study has been carried out on the sub-extracts of it. Next, we tested the effect of sub-extracts of HFE at different concentrations on the survival of E. coli O157:H7at 37°C for a week. Of the 5 sub-extracts, HFEC, HFEB and HFER were observed to be inactive on E. coli O157:H7at all concentrations. However, both of at 2.0 and 2.5% concentrations HFEEA extract showed a partial inhibition on growth of the pathogen on the fifth and the seventh day, respectively. In the same way, HFEH extract started its bacteriostatic or bactericidal effect on the seventh day at a concentration of 2.5%.

References: [1] Sezik, E. et al. (1991). Journal of Ethnopharmacology 35: 191–196. [2] Fujita, T. et al. (1995). Economy Botany 49: 406–422. [3] Sezik, E. et al. (2001). Journal of Ethnopharmacology. 75: 95–115.