Levels of selenium, dl-α-tocopherol, dl-γ-tocopherol, all-trans-retinol, thymoquinone and thymol in different brands of Nigella sativa seeds

The seeds of Nigella sativa are used commonly in the Middle East as a traditional medicine to treat a variety of health conditions. This paper examines the levels of selenium, dl-α-tocopherol, dl-γ-tocopherol, all-trans-retinol, thymoquinone and thymol in different brands of N. sativa seeds purchased from local markets in Riyadh, Saudi Arabia. Selenium was determined by the inductively coupled plasma spectrometry coupled with the hydride system. dl-α-tocopherol, dl-γ-tocopherol, all-trans-retinol, thymoquinone and thymol were measured by high-performance liquid chromatography. The average mean concentrations (mg/kg fresh weight) of selenium, dl-α-tocopherol, dl-γ-tocopherol, all-trans-retinol, thymoquinone and thymol in all tested seeds were 0.17±0.10, 9.02±4.84, 5.42±3.96, 0.27±0.27, 2224.49±1629.50 and 169.35±100.12, respectively. The concentrations of these analytes were significantly affected by the country of origin of the N. sativa. It is concluded that N. sativa provides an important source of antioxidants.