Abstract

This study aimed at investigating the phytoconstituents of methanol leaf extract of Senna obtusifolia and their antibacterial activities against Staphylococcus aureus and Salmonella typhi. Leaves of Senna obtusifolia were collected around Kufaina, Zaria, and pure cultures of test organisms were obtained from the Department of Veterinary Microbiology, Ahmadu Bello University, Zaria. The leaves were shed, dried at room temperature, then powdered with a pestle and mortar. Muller-Hinton Agar and Peptone water were used to determine whether the extract inhibited growth or killed the test bacteria. The leaf extract showed presence of Saponins, Tannins, Flavonoids, Cardiac glycosides, Steroids, and Alkaloids. However, Phenols, Triterpenes, and Anthraquinones were not detected. The extract showed remarkable antibacterial activity against the organisms, with Salmonella typhi exhibiting three zones of inhibition at concentrations of 125 mg/mL, 250 mg/mL, and 500 mg/mL of the extract. While Staphylococcus aureus exhibited two zones of inhibition at concentrations of 250 mg/mL and 500 mg/mL. At the concentrations of 250mg/ml and 500mg/ml, Staphylococcus aureus were killed completely, while Salmonella typhi was only killed at the highest concentration of 500mg/ml, with no turbidity of the testing colonies. This study therefore confirmed the presence and inhibitory effect of the phytochemicals of Senna obtusifolia on the test organisms (S. aureus and S. typhi) and recommended pharmaceutical industries to consider using the leaves of Senna obtusifolia  in developing new medicines/herbal formulations that could treat bacterial infections. Further research also should be done to ascertain the presence or absence of other beneficial or toxic phytochemicals to decide their safety for consumption as food.