The threat of antibiotic-resistance calls for novel antibacterial agents. This study was aimed at screening medicinal plants for their antibacterial properties, phytochemical content and safety. Leaves of Allophylus abyssinicus (Hochst.) Radlk., Dicliptera laxata C.B.Clarke, Ligustrum vulgare L., Solanecio gigas (Vatke) c. Jeffrey and Gymnanthemum myrianthum (Hook.f.) H.Rob.; leaf and stem-bark of Olinia rochetiana A. Juss. and the seed of Cucurbita pepo L. were used. Chloroform and ethanol were used to extract G. myrianthum, D. laxata and O. rochetiana; ethyl acetate and methanol for the rest, and water for all. The extracts were tested against clinical/standard strains of Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Staphylococcus aureus by the agar-diffusion method. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined. Acute toxicity to mice was checked and preliminary phytochemical screening was done. Thirteen extracts, out of 24, were active (inhibition zone >7 mm) at differing levels (9.67±0.33-25.66±0.57 mm) against at least one bacterial strain. The MICs and MBCs were 1.95-15.6 mg/mL and 7.8-125 mg/mL respectively. The aqueous extract of S. gigas, methanol extracts of L. vulgare and A. abyssinicus, and ethanol extract of O. rochetiana leaf were the most active (MIC 1.95mg/ml) against S. aureus. Ethyl acetate extracts of A. abyssinicus, L. vulgare and S. gigas; aqueous of C. pepo, O. rochetiana and G. myrianthum; and all D. laxata had no antibacterial activity. P. aeruginosa was the least susceptible to any extract, although the methanol and aqueous extracts of S. gigas performed better against it. Preliminary phytochemical screening of selected extracts for phenols, flavonoids, tannins, steroids, terpenoids, steroidal glycosides, alkaloids, saponins, resins and glycosides showed positivity at least for four of these phytochemicals with glycoside and terpenoids in nearly all extracts and resin in none. The plants were not toxic to mice at 2000 mg/kg. Further consideration of S. gigas, L. vulgare, A. abyssinicus and O. rochetiana is recommended in light of their promising potential and safety.

In the past with the advent of antibiotics, bacterial diseases have been under control. However rapid spread of antibiotic-resistant this success is reversing and searching for newer antibacterial agents is currently a top priority. This study was, thus, aimed at assessing the anti-microbial activities of two traditional medicinal plants: Vernonia myriantha and Olinia rochetiana. The crude extracts were tested for their in vitro antibacterial activities and phytochemical content. The extracts were tested against selected 3 clinical and 4 standard test bacterial strains by using agar well-diffusion method and the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). The ethanol leaves and stem-bark extracts of O. rochetiana inhibited the growth of all bacterial strains at a concentration of 250mg/mL. The inhibition zones ranged from 20.33±0.57mm for clinical Pseudomonas aeruginosa to 25.66±0.57mm for standard Salmonella typhi strains. The values for these same extracts were 20.66±2.51mm and 24.33±1.15mm for standard P. aeruginosa and Staphylococcus aureus strains respectively. The chloroform extract was similarly effective against all of the strains with inhibition zones between 19.00±1.73mm against P. aeruginosa and 22.66±2.51mm for S. aureus. Comparatively, the ethanol extract of O. rochetiana had the highest MIC (7.81mg/mL) and MBC (62.50mg/mL) were noted against P. aeruginosa. On the other hand, chloroform extract of O. rochetiana leaf showed the highest MIC (15mg/mL) and MBC (125mg/mL) were recorded against P. aeruginosa. The ethanol extract of V. myriantha showed growth inhibition only on S. aureus (21.00±1.7mm). Both plants tested for terpenoids and glycosides showed positive result, but none for resin.