Antibacterial efficacy of Cassia seena sp. leaf extracts against Staphylococcus aureus and Escherichia coli: a phytochemical and toxicological evaluation.

The rising antimicrobial resistance of clinically relevant organisms, such as Staphylococcus aureus and Escherichia coli, has triggered researchers' attention to natural medicinal plants as an alternative source of antibacterial agents. The purpose of this study was to evaluate the antibacterial, phytochemical, and toxicological activities of Cassia senna leaf. The n-hexane, methanolic, and aqueous extracts of Cassia leaves were assayed for antibacterial activity using agar well diffusion, disc diffusion, and broth microdilution assays with gentamicin, vancomycin, and chloramphenicol. The major bioactive components of the extract were identified using thin-layer chromatography (TLC) coupled with bioautography, while phytochemical screening was done on the methanolic extract. Sub-chronic (30-day repeated-dose) toxicity was evaluated in mice that received 1000 mg of the methanolic extract per kg of body weight per day for 30 consecutive days, monitoring the changes in body weight, organ appearance, blood cell count, biochemical profiles, and histology. While the S. aureus isolate was sensitive to all three reference antibiotics, the E. coli isolate was resistant to them. The methanolic extract demonstrated better antibacterial activity than the aqueous extract, as it produced bigger inhibition zones and lower minimum inhibitory concentrations than the aqueous one, while n-hexane extract did not show any antibacterial activity. The activity of Cassia senna leaf extract was higher against S. aureus than Gram-negative E. coli. TLC-bioautography revealed that there were at least four compounds in the methanolic extract that contributed to its antibacterial activity, while phytochemical screening of the methanolic extract showed that it contained flavonoids and tannins, but not phenolics, saponins, alkaloids, or terpenoids. Finally, the 30-day sub-chronic toxicity study revealed that repeated oral administration of 1000 mg/kg/day of Cassia senna leaf extract did not cause any mortality or adverse effect in mice, with the treated animals showing comparable results to the control group in terms of body weight, organ appearance, blood cell count, biochemical profile, and histology. The present study demonstrated that Cassia senna leaves had a considerable antibacterial effect, especially against S. aureus isolate, and were safe and tolerable in mice at a repeated oral dose of 1000 mg/kg/day for 30 days. Therefore, it can be suggested that Cassia leaf extract can be further explored as a promising source of antibacterial compounds.