Abstract

---

Senna occidentalis is widely used by herbalists in northern Nigeria for the treatment of microbial diseases. This study determined the phytochemical constituents and antibacterial activities of aqueous extracts of the leaf and seed of S. occidentalis against some selected clinical pathogens. The Leaf and seed were reduced to powder and extracted by maceration using sterile distilled water. Extracts were concentrated using rotary evaporator and freeze drier. Phytochemical screening was conducted using standard methods while antibacterial activities were determined using the agar well diffusion method. The diameter of the zones of inhibition of bacterial growth was assessed as an index for antibacterial properties of the extracts against the selected bacteria. The phytochemical screening of the leaf and seed revealed the presence of flavonoids (33 % and 22 %), alkaloids (3.6% and 6%), saponins (1.2 % and 2.1 %), phenols (0.036 mg/mL and 0.042 mg/mL) and glycosides (2.68 mg/mL and 2.02 mg/mL) respectively, while steroids and tannins were absent in both. Both leaf and seed extracts exhibited significant (p<0.05) antibacterial activities at all the concentrations used (200mg/mL, 150mg/mL, 100mg/mL, and 50mg/mL) against the selected Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Salmonella Typhi, Escherichia coli, and Pseudomonas aeruginosa) as compared to the standard antibiotic (Amoxicillin 10mg/mL) used as positive control. The antibacterial activities of the extracts increased significantly with increase in concentration for all organisms and the seed extracts were most active with mean inhibitory activity between 19-32mm compared to the leaf extracts with mean inhibitory activity between 12-31mm except E. coli where the leaf extracts were more potent (20, 25, 28, 31 mm) than the seed’s (19, 22, 25, 32 mm) at concentrations ≤150 mg/mL. Hence, aqueous extracts of both plant parts possess the potential to be used as antibiotics to treat selected microbial diseases.

Keywords: Antimicrobial activities, phytochemical screening, plant extracts, Senna occidentalis, traditional medicine