title: Antibacterial, antifungal and antioxidant activity of Olea africana against pathogenic yeast and nosocomial pathogens.
abstract: BACKGROUND
  Olea africana leaves are used by Bapedi people to treat different ailments. The use of these leaves is not validated, therefore the aim of this study is to validate antimicrobial properties of this plant.
  
  
  METHODS
  The ground leaves were extracted using solvents of varying polarity (hexane, chloroform, dichloromethane (DCM), ethyl acetate, acetone, ethanol, methanol, butanol and water). Thin layer chromatography (TLC) was used to analyse the chemical constituents of the extracts. The TLC plates were developed in three different solvent systems, namely, benzene/ethanol/ammonium solution (BEA), chloroform/ethyl acetate/formic acid (CEF) and ethyl acetate/methanol/water (EMW). The micro-dilution assay and bioautography method were used to evaluate the antibacterial activity of the extracts against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus and the antifungal activity against Candida albicans and Cryptococcus neoformans.
  
  
  RESULTS
  Methanol was the best extractant, yielding a larger amount of plant material whereas hexane yielded the least amount. In phytochemical analyses, more compounds were observed in BEA, followed by EMW and CEF. Qualitative 2, 2- diphenylpacryl-1-hydrazyl (DPPH) assay displayed that all the extracts had antioxidant activity. Antioxidant compounds could not be separated using BEA solvent system while with CEF and EMW enabled antioxidant compounds separation. The minimum inhibitory concentrations (MIC) values against test bacteria ranged between 0.16 and 2.50 mg/mL whereas against fungi, MIC ranged from 0.16 to 0.63 mg/mL. Bioautography results demonstrated that more than one compound was responsible for antimicrobial activity in the microdilution assay as the compounds were located at different Rf values.
  
  
  CONCLUSIONS
  The results indicate that leaf extracts of Olea africana contain compounds with antioxidant, antibacterial and antifungal activities. Therefore, further studies are required to isolate the active compounds and perform other tests such as cytotoxicity. Olea africana may be a potential source of antimicrobial compounds.
authors.affiliation: Department of Biochemistry, Microbiology and Biotechnology, University of Limpopo, Private bag X1106, Sovenga, 0727, South Africa. Peter.Masoko@ul.ac.za.
authors.forename: Peter
authors.initials: P
authors.lastname: Masoko
authors.affiliation: Department of Biochemistry, Microbiology and Biotechnology, University of Limpopo, Private bag X1106, Sovenga, 0727, South Africa. polokwanedavid@gmail.com.
authors.forename: David M
authors.initials: DM
authors.lastname: Makgapeetja
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D002855:Chromatography, Thin Layer; D003428:Cross Infection / Q000382:microbiology; D016488:Medicine, African Traditional; D008826:Microbial Sensitivity Tests; D031658:Olea / Q000737:chemistry; D018384:Oxidative Stress / Q000187:drug effects; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry; D015003:Yeasts / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D000975:Antioxidants; D010936:Plant Extracts