Abstract

Background: The increasing antibiotic resistance exhibited by pathogenic microbial infectious agents has led to the screening of several medicinal plants for their potential antimicrobial activity. An in vitro experimental study was conducted with the aim to evaluate antibacterial effect of bark root extracts of S. incanum and C. macrostachyus against S. aureus and E. coli. The experimental study was carried out from November 2018 to April 2019 in Jimma University. The crude extracts of S. incanum and C. macrostachyus were extracted with petroleum ether, ethanol
and distilled water using maceration methods. The antibacterial assay was carried out with agar well diffusion and minimum inhibition concentration.
Results: C. macrostachyus bark root ethanol extracts have generated antibacterial effect against E. coli and S. aureus with maximum zone of inhibition of 15 ± 0.58 mm and 17.33 ± 0.89 mm respectively. However, bark root C. macrostachyus aqueous extracts were showed lowest mean zone of inhibition (9 ± 0.33 mm and 9 ± 0.58 mm) against E. coli and S. aureus respectively. Petroleum ether bark root extract of S. incanum was showed highest zone of inhibition against E. coli (21.33 ± 0.33 mm) than S. aureus (14.67 ± 0.33 mm). S. incanum bark root ethanol extract was generated highest zone of inhibition of 22.33 ± 0.89 mm and 21.33 ± 0.33 mm against S. aureus and E. coli respectively. Aqueous bark root extract of S. incanum and C. macrostachyus had showed lowest zone of inhibition against E. coli and S. aureus. Bark root ethanol extract of S. incanum was generated minimum inhibitor concentration against S. aureus (6.25 mg/ml) and E. coli (12.5 mg/ml) than other solvents. There was statistical difference (p<0.05) between the concentrations of bark root ethanol and petroleum ether extract of Solanum incanum and Croton macrostachyus against S. aureus and E. coli. However, there was no statistical significant difference (p>0.05) between the concentration of S. incanum and C. macrostachyus aqueous extract against E. coli and S. aureus.
Conclusion: Bioactive compounds of medicinal plant extracts have been used to overcome the challenges of antimicrobial resistance. The current experimental study showed that, the bark root extract of Solanum incanum and Croton macrostachyus have high potent of antibacterial activities against E. coli and S. aureus. This study therefore substantiates the use of Solanum incanum and Croton macrostachyus as an antimicrobial medicinal plant.

Keywords: Antibacterial; C. macrostachyus extract; E. coli; S. incanum extract; Solvents; S. aureus