Bioactive Compound Profiling and Antimicrobial Potential of Ritchiea longipedicellata Gilg Root: A Bioassay-Guided GC–MS Investigation

Aims: This study investigated the phytochemical composition, antimicrobial activities and bioactive constituents of Ritchiea longipedicellata Gilg root extracts using bioassay-guided fractionation and gas chromatography-mass spectrometry (GC-MS) to identify potential therapeutic agents against multidrug-resistant (MDR) pathogens. Study Design: Experimental laboratory-based investigation involving phytochemical screening, antimicrobial bioassays, chromatographic purification, and GC–MS characterization. Place and Duration of the Study: The study was conducted at the Departments of Pure and Industrial Chemistry and Microbiology, University of Port Harcourt, Rivers State, Nigeria. Root samples were collected from Okigwe, Imo State, Nigeria, in July 2016, and laboratory analyses were subsequently performed. Methodology: Powdered roots were serially extracted with n-hexane, dichloromethane, ethyl acetate, methanol, and water. Methanol and aqueous extracts were screened for phytochemicals, while antibacterial and antifungal activities were evaluated against selected Gram-positive, Gram-negative, and fungal pathogens using the agar well diffusion method. The most active extract was purified by thin-layer and column chromatography, and the bioactive fraction was characterized by GC–MS. Results: The aqueous extract recorded the highest yield (12.71%), followed by the methanol extract (4.20%). Alkaloids and saponins were detected in both extracts, whereas flavonoids were confined to the methanol extract and phenolic compounds and cardiac glycosides to the aqueous extract. All extracts exhibited concentration-dependent antimicrobial activity, with Gram-positive bacteria generally more susceptible than Gram-negative bacteria. Fraction C displayed the greatest antimicrobial activity. GC–MS identified nine compounds, dominated by 5-(hydroxymethyl)-2-furancarboxaldehyde (71.95%) and 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (14.65%). Conclusion: Ritchiea longipedicellata roots are a promising source of bioactive metabolites with broad-spectrum antimicrobial activity. The identified compounds provide potential lead molecules for developing affordable plant-derived therapeutics against MDR pathogens, thereby supporting Sustainable Development Goal 3 (Good Health and Well-being).