Comparative Study of Antimicrobial Susceptibility and Phytoconstituent Analysis of Newbouldia laevis Root and Stem Barks

Newbouldia laevis is widely used in traditional medicine for managing microbial infections. This study evaluated the phytochemical components and antimicrobial properties of its stem and root bark extracts. Stem and root barks were collected from Agbani, Enugu State, authenticated, dried, pulverized, and extracted using methanol, ethyl acetate, and n-hexane. Qualitative phytochemical screening was conducted using standard methods. Thin Layer Chromatography (TLC) was performed with the three solvent systems. Antimicrobial activity was assessed against Escherichia coli, Staphylococcus aureus, Penicillium marneffei, and Aspergillus flavus using the broth dilution method to determine Minimum Inhibitory Concentrations (MICs). Methanol extracts of both stem and root bark exhibited the highest phytochemical diversity, containing alkaloids, tannins, flavonoids, saponins, steroids, terpenoids, and glycosides. Resins were absent in all extracts. TLC revealed 1–3 spots with retention factor (Rf) values ranging from 0.33 to 0.95 across all solvent systems. The methanol stem extract demonstrated MICs of 6.25 mg/ml against A. flavus, 12.5 mg/ml against P. marneffei, and 25 mg/ml against S. aureus. MICs for the root extract were slightly higher, showing 25–50 mg/ml against bacteria and fungi, with E. coli being the least susceptible (MIC: 50 mg/ml). The findings reveal that methanol extracts of the stem and root bark of N. laevis are rich in bioactive compounds with strong antimicrobial activity, particularly against A. flavus and P. marneffei. In the face of rising multidrug-resistant pathogens, the potent bioactivity of N. laevis supports its therapeutic relevance and positions it as a promising candidate for development into novel antimicrobial agents to address global resistance threats.