Antimicrobial evaluation of methanol and aqueous extracts of Cassia siamea leaf and stem bark

Abstract

Background: The rising incidence of antimicrobial resistance has intensified the search for alternative sources of effective antimicrobial agents. Cassia siamea, a medicinal plant traditionally used across West Africa, has been reported to possess antimicrobial properties, yet studies focusing on solvent-specific efficacy and regional variants such as those from Sierra Leone are limited. Methods: Leaves and stem bark of Cassia siamea were collected and authenticated in Sierra Leone. Methanol and aqueous extracts were prepared by maceration. Standard phytochemical screening was conducted to identify bioactive constituents. Antimicrobial activity was assessed using the agar well diffusion method against Streptococcus pyogenes, Staphylococcus aureus, and Salmonella typhimurium. Minimum inhibitory concentrations (MICs) were determined using serial dilution assays. Results: Phytochemical analysis revealed the presence of flavonoids, tannins, glycosides, steroids, saponins, and phenols, with methanol extracts generally showing higher diversity and intensity of these compounds. Methanolic stem bark extract exhibited strong activity against S. pyogenes and S. aureus, while aqueous leaf extract showed significant inhibition against S. aureus and S. typhimurium. The lowest MIC value (2.5 mg/mL) was observed for the aqueous leaf extract, indicating potent antimicrobial activity. Conclusion: Cassia siamea leaf and stem bark extracts demonstrate considerable antimicrobial potential, particularly those extracted with methanol. These findings validate the plant’s traditional use and highlight its relevance as a source of natural antimicrobial compounds. Further studies are recommended to isolate active constituents and evaluate their pharmacological safety and efficacy in vivo.