Thymbra spicata var. spicata is known as “Zahter ”, “Sater” or “Karabaş thyme in the Southeastern Anatolia Region of Turkey and leaves and flowers are consumed as spices and tea, while young shoots are consumed as salads.This study was carried out to determine the change in essential oil content and chemical compositionduring the daytime of the Thymbra spicata plant in Ermenek district of Karaman.In order to determine the diurnal variation, the harvest was done at 5 different hours during the daytime (6:00, 9:00, 12:00, 15:00 and 18:00) in the flowering period. The harvested plants were dried in the shade and the essential oil contents were determined by Clevenger apparatus by hydro distillation and analyzed by GC-MS. The highest content of essential oil was obtained at 18.00 hours with 2.96% and the lowest one’s was obtained at 12.00 hours with 2.20%.The main components of the essential oil were determined as carvacrol (23.29% - 39.89%), thymol (16.24% - 21.52%) and γ-terpinene (18.01% - 20.90%).

In this study, antioxidant, oxidant and oxidative stress index of Thymbra spicata L. collected from Duhok (Iraq) region were determined. The aerial parts of the plant were extracted with ethanol. Rel Assay Diagnostics kits were used for detect TAS, TOS and OSI values. As a result of the studies, it was determined that TAS value of plant extract was determined 8.399±0.102, TOS value was 6.530±0.115 and OSI value was 0.078±0.001. As a result, it was determined that T. spicata has high antioxidant potential and in this context, can be used as a natural resource.