Inhibition of development, swarming differentiation and virulence factors in Proteus mirabilis by an extract of Lithrea molleoides and its active principle (Z,Z)-5-(trideca-4,7-dienyl)-resorcinol

M. C. CARPINELLA; L. DE BELLIS; M. B. JORAY; V. SOSA; P. M. ZUNINO; S. M. PALACIOS

PHYTOMEDICINE

ELSEVIER GMBH

Año: 2011 vol. 18 p. 994 - 997

0944-7113

Part of our ongoing research on the antibacterial activity of Achyrocline satureioides, this study seeks to better understand the interactions between the metabolites isolated from this plant. For this purpose, the combined effect of 23-methyl-6-O-desmethylauricepyrone (1), quercetin (2) and 3-O-methylquercetin (3), obtained through bioguided fractionation from A. satureioides ethanol extract, was evaluated against Staphylococcus aureus and Escherichia coli. In first place, the antibacterial effect of the combination of flavonols 2 and 3 was assessed, as these showed individual effectiveness lower than or equal to that of the fraction from which they were obtained. When the flavonols were applied together at concentrations of >160 and 3 times below their minimum inhibitory concentration (MIC) values, a synergistic effect (FICI = 0.30) against S. aureus was observed. In addition, compounds 2 and 3, respectively combined at concentrations > 330 and 7 times below their MICs, reduced 1000 times the MIC of compound 1, showing a clear synergistic interaction (FICI = 0.15) in treatments against the Gram (+) bacterium. The most active combination against E. coli showed an additive interaction (FICI = 0.62) between the three assayed compounds 1-3 combined at concentrations of 2 and at least 20 and 13 times below their MICs, respectively. These results indicated the existence of concerted action between these metabolites, evidence of the importance of the synergistic interactions between the components of plant-derived extracts for the control of foodborne bacteria.