Optimisation of ultrasound-assisted extraction of natural antioxidants from mustard seed cultivars.

Background: Modified mustard varieties can produce edible oil with reduced amounts of erucic acid and glucosinolates and enhanced antioxidant potential. Therefore, this work focused on the optimisation of the ultrasound-assisted extraction of compounds with high antioxidant capacity from three white mustard seed cultivars using response surface methodology.

Results: The predicted optimum solvent polarity (57.2, 56.5 and 57.6) and ultrasound power-to-sonication time ratio (4.5, 4.8 and 4.3 W min(-1)) resulted in antioxidant capacities determined by the ferric-reducing antioxidant power (FRAP) assay [54.37, 65.75 and 68.55 mmol Trolox equivalent (TE) kg(-1)] and the 2,2'-diphenyl-1-picrylhydrazyl (DPPH) method (141.65, 175.26 and 185.10 mmol TE kg(-1)) and total phenolics content (23.70, 27.16 and 11.29 mg sinapic acid g(-1)) for extracts obtained from one traditional and two modified mustard seed varieties. The highest FRAP and DPPH values (69.51 and 197.73 mmol TE kg(-1)) revealed 50% methanolic extract prepared from modified mustard seed cultivar without erucic acid and glucosinolates treated with ultrasound for 30 min (ultrasound power/ultrasound time = 4 W min(-1)).

Conclusion: Ultrasound-assisted extraction was found to be a more rapid, convenient and appropriate extraction method with higher yield of antioxidants, shorter time and lower solvent consumption in comparison to conventional extraction.