Olax manii stems were collected in Ikire, Osun State, Nigeria. Using the hydrodistillation process, essential oil was extracted from the stem of Olax manii. To ascertain the chemical composition of the essential oil, Gas chromatography mass spectrometry (GCMS) technique analysis was employed. Using doses ranging from 100 to 25 µg/ml, the antioxidant properties of the essential oil were examined using the 2, 2-Diphenyl-1 picryl hydroxyl (DPPH) radical scavenging activity method. The results of the Gas chromatography mass spectrometry (GC-MS) analysis indicated that the main chemical constituents were squalene (6.18 %), amyrone (4.49%), and neophytadiene (4.22 %). The minor constituents were identified as limonene (0.23 %), caryophyllene (0.31 %) and phytol (1.62 %). The essential oil radical scavenging activity at a concentration of 100 mg/ml was compared to the standard ascorbic acid at the same concentration and it revealed that the essential oil exhibited a significant percentage radical scavenging activity of 78.52 %. The percentage radical scavenging activities increased with increase in concentrations of the essential oil. The Essential oil constituents which possess antioxidant activities could be responsible for the antioxidant activities and ethnomedicinal uses of Olax manii.
