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-alpha-tocopherol, DL-gamma-tocopherol, all-trans-retinol, thymoquinone and thymol in different brands of A 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-alpha-tocopherol, DL-gamma-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-alpha-tocopherol, DL-gamma-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 A sativa. It is concluded that N. sativa provides an important source of antioxidants. (c) 2005 Elsevier Inc. All rights reserved.