Comparative Phytochemical Analysis and Bioactivities of Leaf and Stem Extracts of Nigerian Indigofera spicata

Background and Objective: The chemical composition of medicinal plants can vary across geographical regions, influencing their therapeutic potential. Indigofera spicata, a species widely used in traditional medicine, remains underexplored in Nigeria. This study aimed to comparatively evaluate the phytochemical composition and biological activities of the leaf and stem extracts of I. spicata collected in Nigeria, to identify potential pharmacologically active compounds. Materials and Methods: Leaf and stem samples were extracted using methanol, ethyl acetate, and n-hexane solvents. Phytochemical constituents were screened using standard qualitative assays. Antimicrobial activity was assessed through susceptibility tests, Minimum Inhibitory Concentration (MIC), and Minimum Bactericidal Concentration (MBC) analyses. Antioxidant potential was determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, while cytotoxicity was evaluated using the Brine Shrimp Lethality Assay (BSLA). Statistical analyses were performed using appropriate comparative tests with significance set at p<0.05. Results: The leaf extract contained tannins, flavonoids, and cardiac glycosides, whereas the stem extract contained saponins, alkaloids, steroids, and cardiac glycosides. The stem extract exhibited stronger antimicrobial activity (MIC 0.39 mg/mL; MBC 3.125 mg/mL) against Escherichia coli. It also demonstrated superior antioxidant potential (IC₅₀ = 245.77 μg/mL) compared to the leaf extract (LC₅₀ = 1081.33 μg/mL). Cytotoxicity results indicated higher potency for the stem extract (LC₅₀ = 290 μg/mL) relative to the leaf extract (LC₅₀ = 507.5 μg/mL). Conclusion: The stem extract of Indigofera spicata collected in Nigeria exhibited superior antimicrobial, antioxidant, and cytotoxic properties compared to the leaf extract, suggesting it as a promising source of bioactive compounds for pharmaceutical and medicinal applications. Further isolation and characterization of active constituents are recommended to validate these findings.