title: Antibacterial activity of Aquilaria crassna leaf extract against Staphylococcus epidermidis by disruption of cell wall.
abstract: BACKGROUND
  Aquilaria crassna Pierre ex Lecomte has been traditionally used in Thailand for treatment of infectious diseases such as diarrhoea and skin diseases for a long time. The main objectives of this study were to examine antibacterial activity of the Aquilaria crassna leaf extract against Staphylococcus epidermidis and its underlying mechanism. The antioxidant activity and acute toxicity were studied as well.
  
  
  METHODS
  Antioxidant activities were examined by FRAP, ABTS and DPPH scavenging methods. Antibacterial activity was conducted using disc diffusion assay and the minimum inhibitory concentration (MIC) was determined by dilution method. The minimum bactericidal concentration (MBC) was reported as the lowest concentration producing no growth of microbes in the subcultures. Morphological changes of the microbe were observed by scanning electron microscopy, while an inhibitory effect on biofilm formation was evaluated by phase contrast microscopic analysis. Bacterial cell wall integrity was assessed by transmission electron microscopy. Acute toxicity was conducted in accordance with the OECD for Testing of Chemicals (2001) guidelines.
  
  
  RESULTS
  The extract exhibited considerable antioxidant activity. Staphylococcus epidermidis was susceptible to the extract with the MIC and MBC of 6 and 12 mg/ml, respectively. The extract caused swelling and distortion of bacterial cells and inhibited bacterial biofilm formation. Rupture of bacterial cell wall occurred after treated with the extract for 24 h. Acute toxicity test in mice showed no sign of toxicity or death at the doses of 2,000 and 15,000 mg/kg body weight.
  
  
  CONCLUSIONS
  The aqueous extract of Aquilaria crassna leaves possesses an in vitro antibacterial activity against Staphylococcus epidermidis, with no sign of acute oral toxicity in mice, probably by interfering with bacterial cell wall synthesis and inhibiting biofilm formation.
authors: School of Pharmacology, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
authors: Sirilak
authors: S
authors: Kamonwannasit
authors: Nawarat
authors: N
authors: Nantapong
authors: Pakarang
authors: P
authors: Kumkrai
authors: Prathan
authors: P
authors: Luecha
authors: Sajeera
authors: S
authors: Kupittayanant
authors: Nuannoi
authors: N
authors: Chudapongse
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000009:adverse effects / Q000494:pharmacology*; D002473:Cell Wall / Q000187:drug effects*; D005260:Female; D008297:Male; D051379:Mice; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000009:adverse effects / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry; D013212:Staphylococcus epidermidis / Q000187:drug effects*; D029645:Thymelaeaceae / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D010936:Plant Extracts
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