title: The efficacy and safety of nine South African medicinal plants in controlling Bacillus anthracis Sterne vaccine strain.
abstract: BACKGROUND
  Anthrax is a zoonotic disease caused by Bacillus anthracis, a Gram-positive spore-forming bacterium. The presence of the bacteria and the toxins in the blood of infected hosts trigger a cascade of pathological events leading to death. Nine medicinal plants with good activities against other bacteria were selected to determine their in vitro antibacterial activity against Bacillus anthracis Sterne strain. The cytotoxicity of the extracts on Vero kidney cells was also determined.
  
  
  RESULTS
  The minimum inhibitory concentration (MIC) values of the extracts against Bacillus anthracis Sterne strain ranged from 0.02 to 0.31 mg/ml. Excellent MIC values were observed for the following plant species: Maesa lanceolata (0.02 mg/ml), Bolusanthus speciosus, Hypericum roeperianum, Morus mesozygia (0.04 mg/ml) and Pittosporum viridiflorum (0.08 mg/ml). The total antibacterial activity of the extracts ranged from 92 to 5562 ml/g. Total activity presents the volume to which the extract from 1 g of plant material can be diluted and still inhibit microbial growth. Maesa lanceolata and Hypericum roeperianum had the highest total activity with values of 5562 and 2999 ml/g respectively. The extracts of Calpurnia aurea had the lowest total activity (92 ml/g). The cytotoxicity determined on Vero cells indicated that most of the extracts were relatively non-toxic compared to doxorubicin (LC50 8.3 ± 1.76 μg/ml), except for the extracts of Maesa lanceolata, Elaeodendron croceum and Calpurnia aurea with LC50 values at 2.38 ± 0.25, 5.20 ± 0.24 and 13 ± 2.26 μg/ml respectively. The selectivity index (SI) ranged from 0.02 to 1.66. Hypericum roeperianum had the best selectivity index, (SI = 1.66) and Elaeodendron croceum had lowest value (SI = 0.02).
  
  
  CONCLUSIONS
  The crude acetone extracts of the selected plant species had promising antibacterial activity against Bacillus anthracis. Maesa lanceolata extracts could be useful as a disinfectant and Hypericum roeperianum could be useful to protect animals based on its high total activity and selectivity index. Further investigation of these plant extracts may lead to the development of new therapeutic agents to protect humans or animals against anthrax.
authors.affiliation: Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110, Pretoria, South Africa. leokonti@yahoo.com.|Present address: Drug Development Section, Biochemistry Division, National Veterinary Research Institute, P.M.B. 01, Vom, Plateau State, Nigeria. leokonti@yahoo.com.
authors.forename: Ishaku Leo
authors.initials: IL
authors.lastname: Elisha
authors.affiliation: Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110, Pretoria, South Africa. jpdzoyem@yahoo.fr.|Present address: Department of Biochemistry, Faculty of Science, University of Dschang, P.O. Box 67, Dschang, Cameroon. jpdzoyem@yahoo.fr.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Dzoyem
authors.affiliation: Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110, Pretoria, South Africa. francien.botha@up.ac.za.
authors.forename: Francien S
authors.initials: FS
authors.lastname: Botha
authors.affiliation: Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110, Pretoria, South Africa. kobus.eloff@up.ac.za.
authors.forename: Jacobus Nicolaas
authors.initials: JN
authors.lastname: Eloff
mesh_terms: D000818:Animals; D022122:Anthrax Vaccines; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001408:Bacillus anthracis / Q000187:drug effects*; D002522:Chlorocebus aethiops; D003603:Cytotoxins / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000494:pharmacology*; D010946:Plants, Medicinal; D013019:South Africa; D014709:Vero Cells
chemical_list: D022122:Anthrax Vaccines; D000900:Anti-Bacterial Agents; D003603:Cytotoxins; D010936:Plant Extracts