Phytochemical screening and in vitro evaluation of antibacterial activity of aqueous and ethanolic extracts of root and stem bark of Bridelia ferruginea. Benth. (Euphorbiaceae)

This study aimed at analysing the phytochemical content and antimicrobial activity of Bridelia ferrugine against selected bacteria. Total saponin, alkaloids, tannins, flavonoids and total anthraquinone contents were evaluated using spectrophotometric equivalents of the standards. The antibacterial activity of the plant extracts were determined using Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays against selected bacteria. The root and stem revealed the presence of the phytochemicals tested except the stem that lacked anthraquinones. In vitro antimicrobial activity of the plant extracts against the gram-positive bacteria tested showed that Bacillus cereus was most susceptible to the plant extract having MIC and MBC of 25 and 50 mg/ml, respectively for the stem-bark and root-bark ethanolic extract, while gram-negative bacteria the plant extracts were most active against Proteus mirabilis with MIC and MBC of 50 and 100 mg/ml, respectively. The aqueous extract was most active against Staphylococcus epidermidis with MIC and MBC of 50 and 100 mg/ml for stem-bark and 25 and 50 mg/ml for root-bark extract. Concentration dependent study showed the plant extracts were either bacteriostatic or bactericidal. Only the stem-bark aqueous extract showed no primary effect on the control strains. The study confirmed the presence of some phytochemicals which revealed that the plant is of pharmacological importance going by the ability of these phytochemicals to elicit antibacterial activity. Key words: Antibacterial, phytochemical screening, Bridelia ferruginea, plant extracts.