Number Of Antibacterial Compounds Research Articles

Antibacterial activity of selected medicinal plants used in ethnoveterinary medicine

Five plant species (Balanites maughamii, Breonadia salicina, Dombeya rotundifolia, Hyperacanthus amoenus and Piliostigma thonningii) were extracted with acetone. Antibacterial activity of the leaf extracts of B. maughamii and D. rotundifolia, P. thonningii and bark extracts of B. salicina and H. amoenus were determined using serial dilution assay. The plant species were selected based on information provided by small scale farmers on the use of these plant species against various diseases in the domestic livestock. The crude extracts were tested for antibacterial activity against four selected bacterial strains, one gram positive (Bacillus cereus ATCC 14579) and three gram negative (Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922 and Enterococcus faecalis ATCC 29212). All plant extracts were active against the selected tested bacterial. Of the five plant species, leaf extracts of B. maughamii and P. thonningii had the best antibacterial activity against E. faecalis and P. aeruginosa (MIC value of 0.195 mg/ml). However, addition of polyethylene glycol (PEG) to the plant extracts resulted in reduction of antibacterial activity in all crude extracts, with PEG being more effective than polyvinyl polypyrrolidone (PVPP). The highest percentage reduction (97.8%) was observed in extract of B. maughamii against E. faecalis. Bioautography assay was used to determine the number of antibacterial compounds in the extracts. No active compounds were observed in plant extract of P. thonningii with good antibacterial against microorganisms indicating possible synergism between separated metabolites. Based on our findings, selected plant species could be used by small scale farmers in ethnoveterinary medicine to combat bacterial infections in livestock. Key words: Antibacterial activity, minimum inhibitory concentration, bioautography assay, ethnoveterinary medicine

Five <i>Ochna</i> species have high antibacterial activity and more than ten antibacterial compounds

New measures to control infections in humans and other animals are continuously being sought because of the increasing resistance of bacteria to antibiotics. In a wide tree screening survey of the antimicrobial activity of extracts of tree leaves (www.up.ac.za/phyto), Ochna pulchra, a small tree found widely in southern Africa, had good antibacterial activity. We therefore investigated the antibacterial activity of acetone leaf extracts of some other available Ochna spp. Antibacterial activity and the number of antibacterial compounds in acetone leaf extracts of Ochna natalitia, Ochna pretoriensis, O. pulchra, Ochna gamostigmata and Ochna serullata were determined with a tetrazolium violet serial microplate dilution assay and bioautography against Staphylococcus aureus, Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa, bacteria commonly associated with nosocomial infections. The percentage yields of the extracts varied from 2.5% to 8%. The minimum inhibitory concentrations of the five species ranged from 40 µg/mL to 1250 µg/mL. E. coli was sensitive to all the extracts. The O. pretoriensis extract was the most active with minimum inhibitory concentrations of 0.065 mg/mL and 0.039 mg/mL against E. coli and E. faecalis, respectively. The O. pretoriensis extract also had the highest total activities of 923 mL/g and 1538 mL/g, indicating that the acetone extract from 1 g of dried plant material could be diluted to 923 mL or 1538 mL and would still kill these bacteria. Based on the bioautography results, the two most active species, O. pretoriensis and O. pulchra, contained at least 10 antibacterial compounds with similar R f values. Some of these antibacterial compounds were polar and others were non-polar. Variation in the chemical composition of the species may have some taxonomic value. The order of activity of the species to the bacteria were O. pretoriensis > O. pulchra > O. gamostigmata > O. serullata > O. natalitia. Even before toxicity and bioavailability issues are considered, some Ochna spp. leaf extracts have the potential to be used in treating skin infections.