title: A comparison of the antimicrobial activity and toxicity of six combretum and two terminalia species from southern Africa.
abstract: BACKGROUND
  Plants of the family Combretaceae are amongst the most widely used plants for traditional medicinal purposes in southern Africa. In particular, many species of Combretum and Terminalia are used for their antibacterial, antifungal, antiprotozoal, antiviral, antidiarrhoeal, analgesic, antimalarial, antioxidant, anti-inflammatory and anticancer activities, yet their antimicrobial potential has not been rigorously studied and compared.
  
  
  METHODS
  A survey of antimicrobial activity was undertaken on selected South African Combretum and Terminalia species. Sixteen extracts from 6 Combretum and 2 Terminalia plant species with a history of medicinal usage were investigated by disc diffusion assay against a panel of bacteria and fungi and their MIC values were determined. Toxicity was determined using the Artemia franciscana nauplii bioassay.
  
  
  RESULTS
  All extracts tested displayed broad spectrum antibacterial activity, inhibiting the growth of 12-16 (75-100%) of the bacteria tested, with Gram-positive and Gram-negative bacteria being approximately equally susceptible. Potent antibacterial activities (generally in the range 200-5000 μg/ml) were evident for all Combretaceae extracts against both Gram-positive and Gram-negative bacteria. Similarly, the extracts also displayed good antifungal activity, inhibiting the growth of 2-3 (66.7-100%) of the fungal species tested, with fungal growth inhibition activities generally in the range 200-4000 μg/ml. In general, the Terminalia extracts had better efficacies than the Combretum extracts. Furthermore, the methanol extracts were generally better antimicrobial agents than the water extracts. All extracts were also shown to be non-toxic in the Artemia nauplii bioassay.
  
  
  CONCLUSIONS
  The lack of toxicity of these extracts and their inhibitory bioactivity against a panel of bacteria and fungi indicate their potential as medicinal agents and partially validate their usage in multiple South African traditional medicinal systems.
authors.affiliation: Environmental Futures Research Institute, Nathan Campus, Griffith University, 170 Kessels Rd, Nathan, Queensland 4111, Australia ; Biomolecular and Physical Sciences, Nathan Campus, Griffith University, 170 Kessels Rd, Nathan, Queensland 4111, Australia.
authors.forename: I E
authors.initials: IE
authors.lastname: Cock
authors.affiliation: Department of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, Parktown, South Africa.
authors.forename: S F
authors.initials: SF
authors.lastname: Van Vuuren
keywords: Antibacterial activity; antifungal activity; combretaceae; combretum; terminalia; toxicity