Chemical Composition, Antimicrobial and Antioxidant Activities of Dioscorea dumetorum (Bitter Yam) Leaves and Stem Essential Oil

Background: Dioscorea dumetorum (bitter yam) is an underutilized West African species valued for its nutritional and ethnomedicinal importance. While its tubers have been extensively studied, the essential oils of its aerial parts remain largely unexplored. This study investigated the chemical composition, antimicrobial activity, and antioxidant potential of essential oils extracted from the leaves and stems of Dioscorea dumetorum, to provide scientific insight into their bioactive properties and industrial relevance. Methods: Leaves and stems were air-dried, pulverized, and hydro distilled using a Clevenger-type apparatus. Oil yields and physicochemical properties were determined, while chemical constituents were characterized by Gas Chromatography–Mass Spectrometry (GC-MS). Antimicrobial activity was evaluated against selected bacterial (Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Salmonella typhi, Pseudomonas aeruginosa, Klebsiella pneumoniae) and fungal (Candida albicans, Aspergillus niger, Penicillium notatum, Rhizopus stolonifer) pathogens using the agar well diffusion method. Antioxidant potential was assessed by Ferric Reducing Antioxidant Power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays. Results: The leaf and stem oils yielded 0.50% and 1.07%, respectively. GC-MS analysis revealed 23 and 20 compounds dominated by 2-pentadecanone (20.64%) and phytol (16.74%) in the leaf oil, and di-n-octyl phthalate (34.43%) and eicosanoic acid esters (15.97%) in the stem oil. Both oils exhibited broad-spectrum antimicrobial effects, with leaf oil showing larger inhibition zones (18–26 mm) than stem oil (14–24 mm). Antioxidant assays demonstrated concentration-dependent activities: leaf oil showed stronger ferric-reducing power, whereas stem oil displayed higher radical-scavenging potential. Conclusions: These findings demonstrated that Dioscorea dumetorum essential oils possess significant antimicrobial and antioxidant properties with distinct phytochemical profiles, supporting their potential applications as natural sources of bioactive compounds in nutraceutical, pharmaceutical, and cosmetic formulations.