Gas Chromatography-mass Spectrometry (GC-MS) Profiling and Antibacterial Activity of Newbouldia laevis Root Methanol Extract against ESKAPE Pathogens

Abstract

Background: The emergence and rapid spread of ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) represent a critical global health crisis due to their remarkable multidrug resistance profiles. Newbouldia laevis (Bignoniaceae) is a medicinal plant widely used in African traditional medicine for treating various infectious diseases. This study investigated the phytochemical composition of N. laevis root methanol extract using Gas Chromatography-Mass Spectrometry (GC-MS) and evaluated its antibacterial activity against clinical ESKAPE isolates. Methods: Root samples of N. laevis were collected, authenticated, air-dried, pulverized, and extracted by cold maceration using 80% methanol according to established protocols. Phytochemical profiling was performed using GC-MS analysis. Antibacterial activity was evaluated against clinical isolates of ESKAPE pathogens using agar well diffusion and broth microdilution methods to determine zones of inhibition (ZOI) and minimum inhibitory concentrations (MICs). A total of six clinical isolates (one per ESKAPE species) were tested, with all assays performed in triplicate. Results: GC-MS analysis revealed the presence of 24 bioactive compounds, with γ-sitosterol (24.50%), stigmasterol (12.30%), betulinic acid (8.20%), and ursolic acid (6.80%) as the major constituents. The methanol extract demonstrated significant antibacterial activity against all ESKAPE isolates, with ZOI ranging from 12.3 ± 1.2 mm to 28.6 ± 1.8 mm and MIC values between 62.5 and 500 µg/mL. S. aureus exhibited the highest susceptibility (MIC: 62.5 µg/mL), while E. faecium showed relative resistance (MIC: 500 µg/mL). Conclusion: N. laevis root methanol extract contains diverse bioactive compounds with substantial antibacterial activity against clinically relevant ESKAPE pathogens. These findings support the ethnomedicinal use of N. laevis and highlight its potential as a source of lead compounds for developing novel antimicrobial agents against multidrug-resistant infections.