Preliminary Antimicrobial Profile of Solanum incanum L.: A Common Medicinal Plant

Abstract

Medicinal plants and plant remedies have been in use in Ethiopia for centuries. Studies on ethnobotany, ethnomedicine, and ethnoveterinary estimate that nearly 80% of Ethiopians use some type of medicinal plants and plant remedies. Medicinal plants are regarded as the most important and sometimes the only source of therapeutics in the country. Some 800 plant species are used as sources of medicine to treat about 300 physical and mental disorders. However, because these plant species are not adequately studied, there is a big limitation in their documentation, profiling, and management. Moreover, there is a continuous loss of knowledge about medicinal plants because the communities and people are adopting new lifestyles. Hence, this article reports the finding of a study aimed at providing the gross phytochemical characteristics and antimicrobial activities of ethanol and aqueous extracts of fruit, leaf, and stem of Solanum incanum L. against two Gram-negative (Escherichia coli and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacteria for developing gross antimicrobial profile of the plant. Phytochemical screening of fruit, leaf, and stem extracts of S. incanum has shown that it is the source of alkaloids, saponins, flavonoids, glycosides, terpenoids, and steroids. According to agar disc-diffusion tests, 100 mg/mL extracts of the plant produced bacterial growth inhibition zones of 0.00 to 16.06 mm. Ethanol and aqueous leaf extracts produced inhibition zones ranging from 11.34 to 16.06 mm against all bacterial species. The greatest inhibition zone of 16.06 mm was recorded in E. coli subjected to ethanol leaf extract. The same extract resulted in a growth inhibition zone of 16.04 mm in S. aureus. The greatest growth inhibition zones in B. subtilis (13.34 mm) and S. typhi (11.56 mm) were observed with ethanol leaf and fruit extracts, respectively. Aqueous leaf extracts produced growth inhibition zones ranging from 10.45 mm (for S. typhi) to 14.02 mm (for E. coli). Ethanol leaf extracts resulted in the lowest Minimum Inhibition Concentration (MIC) of 1.56 mg/mL in E. coli and S. aureus. Therefore, fruits, leaves, and stems of S. incanum can be regarded as good sources of some bioactive compounds. The findings are important for taking measures for conservation and sustainable use of the plant as well as for further elucidation of its phytochemistry and antimicrobial efficacy of its constituents.