Oil extraction
Unhulled silflower seeds (700 g) were ground, and hexane (2.5 L) was added. The mixture was heated at 55 °C in an oven for 6 h, filtered, and the solvent was evaporated with a rotary evaporator. The defatted meal was extracted again with hexane (2.5 L) at 55 °C for 3 h. The combined oil was dissolved in 200 ml hexane, stored in a freezer (-20 °C) overnight, and filtered. Solvent was removed with a rotary evaporator and then a vacuum pump. The exactly the same conditions were used to extract oil from unhulled sunflower seeds. The oils were stored under argon until analyses. Oil contents are reported as the average values of duplicate extractions.