Phytochemical profiling and in-vitro antibacterial activity of Croton macrostachyus Hochst. ex Delile leaf and stem bark extracts against selected human pathogens

Medicinal plants have long been utilized for their antiseptic, antiallergic, antibacterial, and antiviral properties in the treatment of human diseases. Croton macrostachyus is a prominent medicinal plant widely used in traditional African medicine for the treatment of various diseases like malaria, tuberculosis, cough, diabetes, rabies and dysentery. This study aimed to investigate the in-vitro antibacterial activity of ethanol, methanol and ethyl acetate extracts derived from the leaves and stem bark of C. macrostachyus against selected human bacterial pathogens. Crude extracts were prepared using the maceration method with the aforementioned solvents. Antibacterial activity, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were determined following clinical laboratory standards institute guidelines. Additionally, qualitative phytochemical analyses were also performed using the standard protocols. All extracts exhibited the inhibitory against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, with S. aureus showing the highest susceptibility. The antibacterial effect was concentration dependent, and leaf extracts demonstrated greater activity compared to stem bark extracts. Among the tested solvents, the methanolic crude extracts ahowed the strongest antibacterial activity. The MIC values of leaf extracts ranged from 0.625 to 2.25 mg/mL while MBC values ranged from 1.25 to 5 mg/mL. Phytochemical analysis of leaf extracts revealed the presence of tannins, alkaloids saponins, flavonoids, glycosides and phenolic compounds in ethanol and methanol based extraction, whereas alkaloids were absent in ethyl acetate based extraction. In contrast stem bark extracts contained glycosides across all solvents, while alkaloids, flavonoids, and phenolic compounds were absent. Tannins and saponins were detected in ethanol and ethyl acetate extracts but not in methanol extracts. Therefore, the present research concludes that the leaf extracts of C. macrostachyus exhibited highest antibacterial activity compared to stem bark extracts. The presence of bioactive phytochemicals supports the traditional use of C. macrostachyus in the treatment of various diseases.