10,126 research outputs found
Chemical composition and anti-biofilm activity of burdock (Arctium lappa L Asteraceae) leaf fractions against Staphylococcus aureus
Purpose: To determine the chemical composition and anti-biofilm activity of burdock leaf fractions against Staphylococcus aureusMethods: The anti-biofilm activity of burdock leaf fractions obtained by column chromatography against S. aureus was determined by minimum inhibitory concentration (MIC). Scanning electron microscopy was employed to further investigate the inhibitory activity. Analysis of the chemical composition of the fractions was performed by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS).Results: The 20 and 34 % ethanol fractions each inhibited the formation of biofilm by S. aureus, with half maximal inhibitory concentration (IC50) ranging from 110 to 150 μg/ml. The 70 % ethanol elution fraction exhibited the strongest inhibitory activity against biofilm formation with IC50 of 13 μg/ml. The minimum inhibitory concentration of the 70 % ethanol fraction completely inhibited the formation of biofilm at a concentration of 0.5 mg/ml, which was lower than the MIC for the growth of the test bacterium (1.25 mg/ml). Scanning electron microscopy (SEM) showed that there was no biofilm formation for cultures treated with burdock leaf fraction, thus confirming the inhibitory efficiency of burdock leaf fraction against biofilm formation. UPLC-MS data identified five active compounds, namely, :caffeic acid, p-coumaric acid, cynarin, quercetin and luteolin.Conclusion: The biofilm formation inhibitory effect of burdock leaf was not only due to its inhibitory effect on bacterial growth but appear to be influenced by its effect on bacterial surface hydrophobicity, and aggregation. Thus, the leaf fractions may be useful in the control of biofilms.Keywords: Biofilm, Staphylococcus aureus, Arctium lappa, Burdock leaf, Scanning electron microscope, Ultra-performance liquid chromatography-mass spectrometr
New variable separation approach: application to nonlinear diffusion equations
The concept of the derivative-dependent functional separable solution, as a
generalization to the functional separable solution, is proposed. As an
application, it is used to discuss the generalized nonlinear diffusion
equations based on the generalized conditional symmetry approach. As a
consequence, a complete list of canonical forms for such equations which admit
the derivative-dependent functional separable solutions is obtained and some
exact solutions to the resulting equations are described.Comment: 19 pages, 2 fig
Approximate perturbed direct homotopy reduction method: infinite series reductions to two perturbed mKdV equations
An approximate perturbed direct homotopy reduction method is proposed and
applied to two perturbed modified Korteweg-de Vries (mKdV) equations with
fourth order dispersion and second order dissipation. The similarity reduction
equations are derived to arbitrary orders. The method is valid not only for
single soliton solution but also for the Painlev\'e II waves and periodic waves
expressed by Jacobi elliptic functions for both fourth order dispersion and
second order dissipation. The method is valid also for strong perturbations.Comment: 8 pages, 1 figur
Secure localization against wormhole attacks using conflicting sets
2010-2011 > Academic research: refereed > Refereed conference paperAccepted ManuscriptPublishe
A novel secure localization approach in wireless sensor networks
2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Elicitation of broadly neutralizing HIV-1 antibodies by guiding the immune responses using primary and secondary immunogens
Abstract also published in AIDS Research and Human Retroviruses. November 2013, 29(11): A-44. doi:10.1089/aid.2013.1500Poster presentationpublished_or_final_versio
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