Sileshi Degu*, Abiy Abebe, Negero Gemeda and Adane Bitew
Background: Infections due to a variety of bacterial etiologic agents have become common and represent a large share of morbidity and mortality. On the other hand, the development of antibacterial drug resistance has been commonly reported worldwide. As a solution to these problems, scientific studies have to be conducted on traditional medicinal plants to develop new, effective and safe antimicrobial drugs since plants are important sources. Traditionally, the study plant (I. tinctoria A. Rich) has been used to treat fungal infections such as ring worms that cause tinea pedis, and it also has different medicinal values. These were some of the provoking information to undertake the evaluation of antibacterial activities with its oral acute toxicity study. Objectives: To evaluate the antibacterial activities and acute oral toxicity of aqueous, ethanol and ethyl acetate root extracts of Impatiens tinctoria A. Rich. Methods: The roots of Impatiens tinctoria A. Rich were extracted using solvents of water, ethanol and ethyl acetate. Agar well diffusion for preliminary antibacterial screening and agar dilution methods for determination of minimal inhibitory concentration were used. The minimum bactericidal concentration of the extracts was determined. By taking inoculums from all concentrations of the plant extract plates exhibiting invisible growth (from inhibition zone of minimal inhibitory concentration plates) and subcultures onto appropriate media plates. Finally, the plant extracts were subjected to oral acute toxicity study according to the organization of economic cooperation and development test Guidelines 420. Result: Gram-positive bacteria were more susceptible to the extracts compared to gram-negative bacteria, especially against S. aureus and S. epidermis, which are commonly found in the skin, even though the traditional application is to control fungal infections and toughen the skin. Ethyl acetate extract was more potent than ethanol and aqueous extracts. The LD50 was above 9600 mg/kg. Conclusion: This study provides a scientific basis as the root of I. tinctoria A. Rich had promising antibacterial activity in an extract-dependent manner in which ethyl acetate extract showed better potency. Therefore, the antibacterial potential and practical nontoxicity of the study plant could take the attention of scientific communities for the development of new, effective and safe antimicrobial drugs by further studying the plant in different directions.
