Comparison of different strategies for soybean antioxidant extraction.

Three extraction strategies including Soxhlet extraction, conventional solid-liquid extraction, and ultrasonic-assisted extraction (UAE) were compared for their efficiency to extract phenolic antioxidants from Virginia-grown soybean seeds. Five extraction solvents were evaluated in UAE and the conventional extraction. The soybean extracts were compared for their total phenolic contents (TPC), oxygen radical absorbance capacity (ORAC), and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*)) scavenging activities. The results showed that UAE improved the extraction of soybean phenolic compounds by >54% compared to the conventional and Soxhlet extractions. Among the tested solvents, 50% acetone was the most efficient for extracting soybean phenolic compounds. There was no significant correlation between the TPC and antioxidant activities of the soybean extracts. The extracts prepared by 70% ethanol had the highest ORAC values. Overall, UAE with 50% acetone or 70% ethanol is recommended for extracting soybean antioxidants on the basis of the TPC and ORAC results.