title: A medicinal herb Cassia alata attenuates quorum sensing in Chromobacterium violaceum and Pseudomonas aeruginosa.
abstract: Quorum sensing (QS) has been shown to play a crucial role in the pathogenesis in many bacteria, and attenuation of QS is one of the targets of antimicrobial therapy with particular interest in combating drug resistance. This study reports the QS inhibitory activity of metabolites from Cassia alata L. (Ca. alata), an important medicinal herb widely used in the treatment of microbial infections. For investigating the QS inhibition (QSI), the potential of Ca. alata L., initially, metabolites of the leaves extracted using ethanol was tested against biosensor strain Chromobacterium violaceum CV026 and C. violaceum wild-type strains. Furthermore, a purified fraction rich in flavonoids (F-AF) was used for establishing QSI activity by studying the inhibition of violacein production in C. violaceum, and QS controlled virulence and biofilm formation in Pseudomonas aeruginosa PAO1. The study results showed 50% inhibition of violacein production in C. violaceum at 0·05 mg ml-1concentration of F-AF. In P. aeruginosa PAO1, it inhibited the tested virulence factors and biofilm formation significantly. The F-AF contained major flavonoids namely, quercetin, quercetrin and kaempferol displaying QSI activity individually against the test organisms.
  
  
  CONCLUSIONS
  Present study demonstrates the quorum sensing inhibitory activity of metabolites from Cassia alata, an important medicinal herb which is commonly used worldwide in the treatment of infections caused by microorganisms. An extract prepared from the leaves of the plant showed activity against quorum sensing in Chromobacterium violaceum and was also effective against attenuating the quorum sensing controlled virulence factors in Pseudomonas aeruginosa. Activity is attributed to the rich flavonoid composition of the plant. Results of the present investigation throw an insight into the possibility of developing drug formulations using the isolated compounds against infections caused by quorum sensing-mediated pathogenicity of bacteria.
authors.affiliation: Yenepoya Research Centre, Yenepoya University, Deralakatte, Mangalore, India.
authors.forename: P D
authors.initials: PD
authors.lastname: Rekha
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: C
authors.initials: C
authors.lastname: Vipin
authors.affiliation: Yenepoya Research Centre, Yenepoya University, Deralakatte, Mangalore, India.
authors.forename: K
authors.initials: K
authors.lastname: Saptami
authors.affiliation: Yenepoya Research Centre, Yenepoya University, Deralakatte, Mangalore, India.
authors.forename: A B
authors.initials: AB
authors.lastname: Arun
mesh_terms: D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002366:Cassia / Q000737:chemistry*; D002861:Chromobacterium / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D053038:Quorum Sensing / Q000187:drug effects*; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D005419:Flavonoids; D010936:Plant Extracts; D037521:Virulence Factors
keywords: 
  Pseudomonas aeruginosa
  ; biofilm; plant metabolite; quorum sensing inhibition; virulence