Neutral lipid classes of black cumin (Nigella sativa L.) seed oils

Abstract.

n-Hexane (H) and chloroform:methanol (CM) were used to extract the oils of Nigella sativa L. seeds. A combination of column and thin-layer chromatography procedures on silica gel were performed to fractionate the main neutral lipid classes of seed oils. The fatty acid pattern of neutral lipid (NL) fractions, triacylglycerol (TAG) and sterol content were determined. NLs constituted 97.2% and 96.1% of total H and CM extract, respectively. TAGs were the major neutral lipid class (80.8–83.1% of the total NLs), while the NL profile was characterized by high levels of free fatty acids (14.3–16.2% of the total NLs). Linoleic acid (C18:2) was the predominant fatty acid followed by oleic (C18:1) and palmitic (C16:0) acids in all examined classes. A good resolution of the TAG critical pairs was accomplished employing a gas liquid chromatograph equipped with a flame ionization detector. The separation of the TAG critical pairs C48:0, C50:1, C52:2 and C54:3 [equivalent carbon number (ECN)=48] as well as C42:0, C48:3 and C54:6 (ECN=42) was accomplished without the aid of any interacting ion such as silver. Six TAG species were determined, but two of them, C54:3 (ECN=48) and C54:6 (ECN=42) were present to the extent of 74% or above of the total TAG content. The 4-desmethylsterols isolated from the unsaponifiable fractions were β-sitosterol (1135–1182 µg/g oil) as the main component followed by Δ5-avenasterol (925–1025 µg/g oil), and Δ7-avenasterol (615–809 µg/g oil). Stigmasterol, campesterol, and lanosterol were detected in small amounts.