title: Some Strychnos spinosa (Loganiaceae) leaf extracts and fractions have good antimicrobial activities and low cytotoxicities.
abstract: BACKGROUND
  Strychnos spinosa Lam. is a deciduous tree used in traditional medicine to treat infectious diseases. This study is designed to determine the antimicrobial, antioxidant and cytotoxic activities of extracts and fractions from leaves of S. spinosa.
  
  
  METHODS
  Extracts were obtained by maceration with acetone, methanol and dichloromethane/methanol (1/1) while fractions were prepared by liquid-liquid fractionation of the acetone extract. A broth serial microdilution method with tetrazolium violet as growth indicator was used to determine the minimum inhibitory concentration (MIC) against fungi, Gram-positive and Gram-negative bacteria. The antioxidant activity was determined using free-radical-scavenging assays, and the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay was used to determine cytotoxicity.
  
  
  RESULTS
  Four extracts and five fractions had good to weak antimicrobial activity with MICs ranging from 0.04 to >1.25 mg/ml against both fungi and bacteria. The chloroform and ethyl acetate fractions had an MIC of 0.08 mg/ml against Aspergillus fumigatus. The n-butanol fraction had an MIC of 0.04 mg/ml against Cryptococcus neoformans. The hexane and chloroform fractions had an MIC of 0.08 mg/ml against Staphylococcus aureus. The antioxidant activities were much lower than that of the positive controls. Except for the alkaloid extract, all the extracts and fractions had free-radical-scavenging activity (IC50 ranging from 33.66 to 314.30 μg/ml). The cytotoxicity on Vero cells was reasonable to low with LC50 values ranging between 30.56 and 689.39 μg/ml.
  
  
  CONCLUSIONS
  The acetone extract and the chloroform fraction had the highest antibacterial activity. By solvent-solvent fractionation it was possible to increase the activity against A. fumigatus and to decrease the cytotoxicity leading to a potentially useful product to protect animals against aspergillosis. Our results therefore support the use of S. spinosa leaves in traditional medicine to treat infectious diseases.
authors.forename: Adamu Imam
authors.initials: AI
authors.lastname: Isa
authors.forename: Maurice Ducret
authors.initials: MD
authors.lastname: Awouafack
authors.affiliation: Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa. jpdzoyem@yahoo.fr.
authors.forename: Jean Paul
authors.initials: JP
authors.lastname: Dzoyem
authors.forename: Mohammed
authors.initials: M
authors.lastname: Aliyu
authors.forename: Rabiu AbduSsalam
authors.initials: RA
authors.lastname: Magaji
authors.forename: Joseph Olusegun
authors.initials: JO
authors.lastname: Ayo
authors.forename: Jacobus Nicolaas
authors.initials: JN
authors.lastname: Eloff
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D001232:Aspergillus fumigatus / Q000187:drug effects*; D002522:Chlorocebus aethiops; D003455:Cryptococcus neoformans / Q000187:drug effects*; D006090:Gram-Negative Bacteria / Q000187:drug effects; D029541:Loganiaceae; D008519:Medicine, Traditional; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000009:adverse effects / Q000494:pharmacology*; D018515:Plant Leaves; D013211:Staphylococcus aureus / Q000187:drug effects*; D031451:Strychnos; D014709:Vero Cells
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D000935:Antifungal Agents; D000975:Antioxidants; D010936:Plant Extracts