Chemical Composition and Antioxidant Properties of the Essential Oil of Nigella Sativa L

The chemical composition of the essential oil obtained from N. sativa was analyzed by GC/MS and the components identified were: p-cymene (22.05%) followed by α-thujene (6%), α-pinene (1.11%), camphene (11%), sabinene (1%), β-pinene (7%), β-myrcene (0.21%), α-phellandrene (0.45%), limonene (0.13), γ-terpinene (5.12%), terpinolene (0.23%), camphor (1%), carvone (0.32%), thymoquinone (20.32%), thymol (10.12%), carvacrol (10%), longicyclene (0.9%) and borneol (0.43). The oils were also subjected to screening for their possible antioxidant activity by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Thymol (13.0 ± 0.8 μg/ml), thymoquinone (12.6 ± 0.0 μg/ml) and carvacrol (12.03 ± 0.0 μg/ml) showed appreciable antioxidant activity in DPPH test. Antioxidant activity guided fractionation of the oil was carried out by the TLC-bioautography screening and fractionation resulted in the separation of the main antioxidant compound which were identified as thymoquinone (51%), thymol (25%) and carvacrol (8%). Introduction Essential oils are aromatic oily liquids, volatile, characterized by a strong odour, rarely coloured, and generally with a lower density than that of water. They can be synthesized by all plant organs and therefore extracted from these parts, where they are stored in secretory cells, cavities, canals, epidermic cells or glandular trichomes (Burt 2004; Bakkali et al. 2008). In nature, essential oils play an important role in as antibacterials, antivirals, antifungals, insecticides, herbicides, or have feeding deterrent effects against herbivores by reducing their appetite for such plants. The antioxidant activity of essential oils is another biological property of great interest because they may preserve foods from the toxic effects of oxidants (Maestri et al. 2006). Black cumin (Nigella sativa L.) belongs to Ranunculaceae family. As an aromatic plant, N.sativa is widely grown in different parts of the world and the seeds of black cumin have been used to promote health for countries especially in the Middle East and Southeast Asia (Hedrick 1972). N. sativa seeds yield esters of fatty acids, free sterols and steryl esters (Menounos et al. 1986). The seeds also contain lipase, phytosterols and sitosterol (Duke 1992). During the past few decades, many phytochemical and pharmacological studies have been conducted on N. sativa seeds because of its marked biological activities, antioxidant, anti-inflammatory and antiulcer activity (Ali and Blunden 2003). The biological properties of the essential oils have been found to be directly linked to their chemical compositions, which are influenced by the origin of the plants (Celiktas et al. 2007). An Iranian N. sativa essential oil was found to be dominated by phenylpropanoid components and displayed a trans-anethole chemotype (Nickavar et al. 2003). The main purpose of this study was to investigate the chemical composition of N.sativa essential oil and to determine its antioxidant activity by scavenging of DPPH (2,2-diphenyl-1-picrylhydrazyl) test. Author for correspondence: .