Increasing antimicrobial resistance among clinically relevant organisms such as Staphylococcus aureus and Escherichia coli has driven interest in natural medicinal plants as potential alternative sources of antibacterial agents. This study evaluated the antibacterial potential, phytochemical composition, and sub‑chronic toxicological profile of leaves of Cassia senna to inform future screening and isolation of bioactive compounds.
Leaves of Cassia senna were extracted using three solvents of differing polarity: n‑hexane, methanol, and water (aqueous). These three extracts were carried forward into antibacterial assays to compare activity across solvent types. The methanolic extract was the main subject for phytochemical screening and toxicological testing.
Antibacterial activity was assessed against clinical isolates of S. aureus and E. coli using multiple standard in vitro methods: agar well diffusion, disc diffusion, and broth microdilution assays. Reference antibiotics used for comparative purposes were gentamicin, vancomycin, and chloramphenicol. Minimum inhibitory concentrations (MICs) were determined by broth microdilution.
To identify active constituents within the methanolic extract, thin‑layer chromatography (TLC) coupled with bioautography was performed. Bioautography allowed visualization of zones on chromatograms corresponding to antimicrobial activity, indicating the presence of compounds that inhibited bacterial growth.
Qualitative phytochemical screening was carried out on the methanolic extract. Screening results reported presence of flavonoids and tannins, and absence of phenolics, saponins, alkaloids, and terpenoids in the tested methanolic fraction.
A sub‑chronic oral toxicity study was performed in mice with daily dosing of the methanolic extract at 1000 mg per kg of body weight for 30 consecutive days. Animals were monitored for mortality and overt adverse effects. Outcome measures included changes in body weight, gross organ appearance, complete blood cell counts, biochemical profiles, and histological examination of relevant tissues. The study was conducted under institutional and national guidelines with appropriate ethical approval.
The S. aureus clinical isolate tested in this study was sensitive to all three reference antibiotics (gentamicin, vancomycin, chloramphenicol). In contrast, the E. coli isolate showed resistance to those antibiotics. Among plant extracts, the methanolic extract demonstrated substantially greater antibacterial activity than the aqueous extract, producing larger inhibition zones in diffusion assays and lower MICs in broth microdilution. The n‑hexane extract displayed no detectable antibacterial activity in the applied assays. Overall, antibacterial effect of Cassia senna leaf extract was higher against the Gram‑positive S. aureus than against Gram‑negative E. coli.
TLC coupled with bioautography of the methanolic extract revealed at least four distinct compounds or fractions that contributed to the observed antibacterial activity. Phytochemical screening of the methanolic extract detected flavonoids and tannins, which are classes of compounds commonly associated with antimicrobial properties; the screened methanolic fraction did not show presence of phenolics, saponins, alkaloids, or terpenoids by the reported tests.
During the 30‑day repeated oral dosing at 1000 mg/kg/day, there were no deaths or observable adverse effects in treated mice. Treated animals had comparable body weight trajectories and gross organ appearance relative to control animals. Hematological parameters, biochemical profiles, and histological examinations showed no reported abnormalities attributable to the extract at the tested dose and duration. These findings indicate that, under the conditions described, the methanolic leaf extract of Cassia senna was tolerated in mice.
The study demonstrated that Cassia senna leaf extracts, particularly the methanolic extract, possess measurable antibacterial activity in vitro, with stronger effects against Staphylococcus aureus than against Escherichia coli. TLC‑bioautography implicated at least four active compounds within the methanolic extract, and phytochemical screening identified flavonoids and tannins as constituents. A 30‑day sub‑chronic toxicity study in mice at 1000 mg/kg/day did not reveal mortality or detectable adverse effects. Collectively, these results support further exploration of Cassia senna leaves as a source of antibacterial compounds and justify additional work to isolate, identify, and characterize the active molecules.
Details such as yields of each extract, exact MIC values, chromatographic retention factors, identities or structures of the active compounds, detailed hematological and biochemical numeric results, and species/strain identifiers for the bacterial isolates were not reported in the abstract. Future studies should include full chemical characterization of active fractions, determination of precise MIC and minimum bactericidal concentration values, evaluation across a broader panel of clinical strains (including characterized resistant isolates), dose‑response toxicology, and mechanistic assays to define mode of action.