title: Anti-quorum sensing activity of flavonoid-rich fraction from Centella asiatica L. against Pseudomonas aeruginosa PAO1.
abstract: OBJECTIVE
  Inhibition of quorum sensing (QS), a cell-density dependent regulation of gene expression in bacteria by autoinducers is an attractive strategy for the development of antipathogenic agents.
  
  
  METHODS
  In this study, the anti-QS activity of the ethanolic extract of the traditional herb Centella asiatica was investigated by the biosensor bioassay using Chromobacterium violaceum CV026. The effect of ethyl acetate fraction (CEA) from the bioassay-guided fractionation of ethanol extract on QS-regulated violacein production in C. violaceum ATCC12472 and pyocyanin production, proteolytic and elastolytic activities, swarming motility, and biofilm formation in Pseudomonas aeruginosa PAO1 were evaluated. Possible mechanism of QS-inhibitory action on autoinducer activity was determined by measuring the acyl homoserine lactone using C. violaceum ATCC31532. Anti-QS compounds in the CEA fraction were identified using thin layer chromatography biosensor overlay assay.
  
  
  RESULTS
  Ethanol extract of C. asiatica showed QS inhibition in C. violaceum CV026. Bioassay-guided fractionation of ethanol extract revealed that CEA was four times more active than the ethanol extract. CEA, at 400 μg/mL, completely inhibited violacein production in C. violaceum ATCC12472 without significantly affecting growth. CEA also showed inhibition of QS-regulated phenotypes, namely, pyocyanin production, elastolytic and proteolytic activities, swarming motility, and biofilm formation in P. aeruginosa PAO1 in a concentration-dependent manner. Thin layer chromatography of CEA with biosensor overlay showed anti-QS spot with an Rf value that corresponded with that of standard kaempferol.
  
  
  CONCLUSIONS
  The anti-QS nature of C. asiatica herb can be further exploited for the formulation of drugs targeting bacterial infections where pathogenicity is mediated through QS.
authors.affiliation: Yenepoya Research Centre, Yenepoya University, Deralakatte, Mangalore, India.
authors.forename: H S
authors.initials: HS
authors.lastname: Vasavi
authors.affiliation: Yenepoya Research Centre, Yenepoya University, Deralakatte, Mangalore, India.
authors.forename: A B
authors.initials: AB
authors.lastname: Arun
authors.affiliation: Yenepoya Research Centre, Yenepoya University, Deralakatte, Mangalore, India. Electronic address: dydirectoryrc@yenepoya.edu.in.
authors.forename: P D
authors.initials: PD
authors.lastname: Rekha
mesh_terms: D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000494:pharmacology*; D015374:Biosensing Techniques / Q000379:methods; D028041:Centella / Q000737:chemistry*; D002861:Chromobacterium / Q000187:drug effects; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology*; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology*; D053038:Quorum Sensing / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D005419:Flavonoids; D010936:Plant Extracts
keywords: Centella asiatica; Pseudomonas aeruginosa; quorum sensing; virulence