title: Combating against methicillin-resistant Staphylococcus aureus - two fatty acids from Purslane (Portulaca oleracea L.) exhibit synergistic effects with erythromycin.
abstract: OBJECTIVE
  The aims of this study were to identify the active ingredients from Portulaca oleracea L. (PO) that could provide synergism with antibiotics against methicillin-resistant Staphylococcus aureus (MRSA) and their possible mechanisms of resistance inhibition.
  
  
  METHODS
  High-speed counter-current chromatography (HSCCC) coupled with gas chromatography-mass spectrometry and a panel of laboratory MRSA strains were used for checkerboard and efflux inhibitory assays.
  
  
  RESULTS
  Linoleic and oleic acids were identified from HSCCC fraction 18 of PO with synergistic antibacterial activity when combined with erythromycin against RN4220/pUL5054. Ethidium bromide efflux inhibitory studies revealed that linoleic and oleic acids may interfere the activity of MsrA pump. By comparing among a panel of linoleic and oleic acids analogues, unsaturated fatty acids in salt form with cis configuration and an increase in number of double bonds were found to further increase the antibacterial activity when used alone or in combination with antibiotics.
  
  
  CONCLUSIONS
  This study reported for the first time that two active ingredients, namely linoleic and oleic acids, were identified from PO with synergistic antibacterial activity when combined with erythromycin against MRSA RN4220/pUL5054 and possibly act by inhibiting the efflux pumps of the bacteria cells.
authors.affiliation: Institute of Chinese Medicine, The Chinese University of Hong Kong, Hong Kong, China; State Key Laboratory of Phytochemistry & Plant Resources in West China (CUHK), The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Ben C L
authors.initials: BC
authors.lastname: Chan
authors.forename: X Q
authors.initials: XQ
authors.lastname: Han
authors.forename: Sau Lai
authors.initials: SL
authors.lastname: Lui
authors.forename: C W
authors.initials: CW
authors.lastname: Wong
authors.forename: Tina B Y
authors.initials: TB
authors.lastname: Wang
authors.forename: David W S
authors.initials: DW
authors.lastname: Cheung
authors.forename: Sau Wan
authors.initials: SW
authors.lastname: Cheng
authors.forename: Margaret
authors.initials: M
authors.lastname: Ip
authors.forename: Simon Q B
authors.initials: SQ
authors.lastname: Han
authors.forename: Xiao-Sheng
authors.initials: XS
authors.lastname: Yang
authors.forename: Claude
authors.initials: C
authors.lastname: Jolivalt
authors.forename: Clara B S
authors.initials: CB
authors.lastname: Lau
authors.forename: Ping Chung
authors.initials: PC
authors.lastname: Leung
authors.forename: Kwok Pui
authors.initials: KP
authors.lastname: Fung
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D004917:Erythromycin / Q000494:pharmacology*; D008401:Gas Chromatography-Mass Spectrometry; D019787:Linoleic Acid / Q000737:chemistry / Q000494:pharmacology*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D019301:Oleic Acid / Q000737:chemistry / Q000494:pharmacology*; D010936:Plant Extracts / Q000737:chemistry; D031822:Portulaca
chemical_list: D000900:Anti-Bacterial Agents; D010936:Plant Extracts; D019301:Oleic Acid; D002939:Ciprofloxacin; D004917:Erythromycin; D019787:Linoleic Acid
keywords: fatty acid; linoleic acid; methicillin-resistant Staphylococcus aureus; oleic acid; synergy