title: Ochnaflavone and ochnaflavone 7-O-methyl ether two antibacterial biflavonoids from Ochna pretoriensis (Ochnaceae).
abstract: The acetone extract of Ochna pretoriensis was evaluated for antibacterial activity using bioautography and serial microplate dilution methods against four nosocomial bacterial pathogens namely: Escherichia coli, Staphylococcus aureus, Enterococcus faecalis and Pseudomonas aeruginosa. A bioassay-guided fractionation of the crude extract led to the isolation of two antibacterial biflavonoids, ochnaflavone and ochnaflavone 7-O-methyl ether. Gram-negative bacteria were more sensitive to the isolated compounds than the Gram-positive bacteria (MIC values: 31.3 microg/mL for P. aeruginosa and 62.5 microg/mL for S. aureus). In addition, the isolated compounds were assessed for their potential toxic effects in the MTT toxicity assay using monkey kidney vero cells and Ames genotoxicity test using Salmonella typhimurium strain TA98. LC50 values were 125.9 microg/mL for ochnaflavone and 162.0/microg/mL for ochnaflavone 7-O-methyl ether. The isolated compounds have selectivity index values ranging from 1.29 to 4.03. Selectivity index values higher than one indicate that test samples are less toxic to the host cells than to the pathogens. The biflavonoids did not have any mutagenic effects in the Salmonella/microsome assay without metabolic activation.
authors: Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag x04, Onderstepoort, 0110, South Africa.
authors: Tshepiso J
authors: TJ
authors: Makhafola
authors: Babatunde B
authors: BB
authors: Samuel
authors: Esameldin E
authors: EE
authors: Elgorashi
authors: Jacobus N
authors: JN
authors: Eloff
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D002522:Chlorocebus aethiops; D004396:Coloring Agents; D004354:Drug Screening Assays, Antitumor; D005419:Flavonoids / Q000737:chemistry* / Q000494:pharmacology* / Q000633:toxicity; D006801:Humans; D008826:Microbial Sensitivity Tests; D009153:Mutagens / Q000633:toxicity; D043842:Ochnaceae / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry; D051381:Rats; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics; D013778:Tetrazolium Salts; D013844:Thiazoles; D014709:Vero Cells
chemical_list: D000900:Anti-Bacterial Agents; D004396:Coloring Agents; D005419:Flavonoids; D009153:Mutagens; D010936:Plant Extracts; D013778:Tetrazolium Salts; D013844:Thiazoles; C578811:ochnaflavone 7-O-methyl ether; C090940:ochnaflavone; C022616:thiazolyl blue