Phytochemical profile and antibacterial activity of stem bark extracts of stereospermum kunthianum (pink jacaranda)

Abstract

The global rise of antimicrobial resistance necessitates the search for novel therapeutic agents from natural sources, particularly medicinal plants. Stereospermum kunthianum (Pink Jacaranda) has long been employed in traditional medicine for the treatment of infectious diseases; however, its antibacterial efficacy requires scientific validation. This study investigated the phytochemical constituents and antibacterial activity of stem bark extracts of S. kunthianum. The dried stem bark powder was sequentially extracted with hexane, ethyl acetate, acetone, and methanol using a Soxhlet apparatus. Phytochemical screening revealed the presence of tannins, flavonoids, alkaloids, saponins, terpenoids, phenols, steroids, cardiac glycosides, phlobatannins, and carbohydrates. Antibacterial activity was assessed against clinical isolates of Escherichia coli and Staphylococcus aureus, using standard bioassay methods. The extracts demonstrated variable antibacterial effects, with inhibition zones ranging from 5.0 to 17.0 mm. Ethyl acetate and methanol extracts exhibited the most pronounced activity, particularly against S. aureus and E. coli. Minimum inhibitory concentration (MIC) tests revealed that methanol extract inhibited S. aureus and E. coli at 12.5 mg/ml, while ethyl acetate extract inhibited S. aureus at 12.5 mg/ml and E. coli at 25 mg/ml. Although less potent than chloramphenicol (control), the findings affirm the antibacterial potential of S. kunthianum stem bark and provide scientific support for its ethnomedicinal use. These results highlight its promise as a source of bioactive compounds for drug discovery, warranting further investigation into its safety, mechanism of action, and potential for development into effective antimicrobial agents.