The aim of this study was to determine antioxidant activity of the water and methanol extracts from the aerial parts of Origanum haussknechtii Boiss. (Lamiaceae), which is an endemic to Turkey. The water and methanol extracts of the plant were evaluated for their antioxidant capacity in 2,2-diphenyl-1- picrylhydrazyl (DPPH) radical scavenging, trolox equivalent antioxidant capacity (TEAC) and inhibition of lipid peroxidation with thiobarbituric acid (TBA) assays. In addition, the total phenolic content in both extracts was determined with spectrophotometric method. The extracts were found to have different levels of antioxidant properties in the test models used. Both extracts of the plant were shown to possess DPPH radical scavenging activity compared to reference substances, but that of methanol extract (IC50=1.22 ± 1.25 mg/mL) was found to be more pronounced. In the TEAC assay, the methanol extract displayed higher antioxidant capacity (1.35 ± 0.28 mmol trolox/g) than the water extract. In the TBA method, the methanol extract (IC50=23.62 ± 2.42 μg/mL) also showed higher inhibitory activity on the lipid peroxidation than the water extract when compared to propyl gallate. The results revealed that the methanol extract of O. haussknechtii is a good antioxidant source of natural origin.
Keywords: Lamiaceae, Origanum haussknechtii Boiss., Plant extracts, Antioxidant activity, Total phenolics