in vitro antibacterial activity, preliminary phytochemical screening profile, and in vivo toxicity of seven traditional medicinal plants in ethiopia

The continuous 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 1.95 mg/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 showedpositivity at least for four of these phytochemicals with glycoside and terpenoids in nearlyall extracts and resin in none. the plants were not toxic to mice at 2000 mg/kg. further considerationof s. gigas, l. vulgare, a. abyssinicus and o. rochetiana is recommended in lightof their promising potential and safety.