Synergistic effects of ultrasound and extraction solvent on the bioactive compound in kenaf seed oil

Kenaf seed oil was extracted with 3 different solvents, i.e. hexane, ethanol and aqueous enzymatic medium with or without ultrasonic assistance. The synergistic effects of ultrasound and extraction solvent on the content of bioactive compound in kenaf seed oil was investigated. Results show that ultrasound-assisted extraction with hexane obtained the highest yield (84.71%), while yield with aqueous enzymatic medium was the lowest (51.12%). Two endothermic peaks exhibited on the melting curve of kenaf seed oil at the temperature range - 37 to - 25 °C and - 12 to - 2 °C, respectively. Linoleic, oleic and palmitic acid are the major fatty acids, accounting for above 96% of the total fatty acids. The content of vitamin E, phosphatide, total phenols and sterol are 92.38-105.01 mg/100 g oil, 0.38-22.28 g/kg, 0.51-71.02 mg GAE/100 g and 161.79-533.12 mg/100 g, respectively. The solvent employed has significant effect (p < 0.05) on the thermal property, fatty acid composition and bioactive constituents of the extracted kenaf seed oil. The oil extracted with ethanol contained more nervonic acid and bioactive components such as β-carotene, phosphatide, total phenols and sterols. The introduction of ultrasound reduced the extraction time remarkably. The results demonstrate that extraction with ethanol combined with ultrasound is an effective method to extract kenaf seed oil, as more reasonable fatty acid composition and higher content of bioactive components can be achieved.