Abstract

Essential oil from the rhizomes of Tulbaghia violacea of the family Alliaceae was obtained by hydro-distillation using an all-glass Clevenger-type apparatus. In vitro antioxidant activities of the oil at various concentrations were assessed using 2, 2-diphenyl-1-picryl hydrazyl (DPPH), nitric oxide scavenging, reducing power and lipid peroxidation inhibition assay. The results were compared with butylated hydroxytoluene (BHT) and ascorbic acid. Brine shrimp lethality test was used to determine cytotoxicity of the oil. Gas chromatography/mass spectrophotometer (GC/MS) analyses of oil revealed 7 polysulfides with a pungent garlic-like odor. The principal constituents were dimethy disulfide, dimethy trisulfide, (methyl methylthio) methyl, 2,4-dithiapentane (11.35%) and (methylthio) acetic acid, 2- (methylthio) ethanol, 3-(methylthio)- and propanenitrile (7.20%). The essential oil demonstrated moderate radical scavenging activities. Although, their EC₅₀ value was lower than those of the BHT and ascorbic acid, the value was close to those reported for other Alliaceae family. The LC₅₀value of 12.59 µg/ml obtained showed that the essential oil of T. violacea was toxic. The implication of the toxicity of the oil is discussed.

Key words: Tulbaghia violacea, antioxidant, essential oils, gas chromatography/ gas chromatography-mass spectrophotometer (GC/GC-MS), toxicity.