Phytochemical and Functional Group Characterization of Polyalthia longifolia Extracts from Nigeria and Their Potential in Crude Oil Souring Mitigation

The petroleum industry is increasingly seeking sustainable solutions to microbial challenges due to the limitations of conventional synthetic biocides. This study investigates the bioactive potential of Polyalthia longifolia leaf extracts as a green alternative for mitigating souring in crude oil systems. The extracts were analyzed using phytochemical screening, Fourier-transform infrared spectroscopy (FTIR), and gas chromatography–mass spectrometry (GC-MS) to elucidate their chemical composition. The FTIR results revealed key functional groups indicative of alcohols, phenols, ketones, and aromatic compounds with potential antimicrobial activity. GC-MS profiling identified 14 prominent bioactive compounds, including long-chain alkanes (such as tritetracontane, hexadecane), fatty acid derivatives (e.g., methyl stearate, palmitic acid), phenolics (e.g., 2,4-di-tert-butylphenol), and nitrogenous heterocycles, which are associated with antimicrobial, antioxidant, and pesticidal properties. These constituents suggest synergistic mechanisms for inhibiting sulfate-reducing bacteria (SRB) and limiting hydrogen sulfide (H2S) production. The presence of rare halogenated compounds enhances the biocidal potential of the extract. The findings demonstrate the promise of P. longifolia as a natural and environmentally friendly alternative to synthetic chemical treatments for microbial control in oilfield applications. This study provides a foundation for further development of plant-derived biocides in the context of green oilfield management.