Submitted to: Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/16/2006
Publication Date: 7/7/2007
Citation: Luthria, D.L., Biswas, R., Natarajan, S.S. 2007. Comparison of extraction solvents and techniques used for the assay of isoflavones from soybean. Food Chemistry. 105:325-333. Interpretive Summary: Isoflavones-enriched extracts have been tested in the prevention of a wide range of conditions such as menopause, heart problems, osteoporosis, and breast, prostate, and colon cancers. This article provides a comparison of four commonly deployed and three modified solvent mixtures used for the extraction of isoflavones from soybean seeds. In addition, comparison of six different extraction procedures with an optimized extraction solvent mixture has also been examined. Extraction yields of isoflavones increased by more than 15% with the modified extraction solvent mixture contained 5% dimethyl sulfoxide. The highest total isoflavones recoveries from soybean samples were obtained with a dimethyl sulfoxide:ethanol:water (5:70:25, % v/v/v) solvent mixture using a pressurized liquid extractor. Improved estimation of isoflavones content of soybean seeds will enable researchers to accurately evaluate the role of isoflavones in health and develop better dietary and safety guidelines on consumption of isoflavones.
Technical Abstract: The impact of extraction solvents and techniques on the assay of isoflavones from soybean was investigated. This systematic study was undertaken to address substantial variations in the solvents and procedures used for the extraction of isoflavones from soybeans by different research groups as described in the recent peer-reviewed published literature. Comparison of four previously optimized and commonly deployed solvent mixtures (acetonitrile:water 58:42 (v/v); ethanol:water 70:30 (v/v); methanol:water 90:10 (v/v); superheated pressurized water) was carried out for the extraction of isoflavones. In addition, we also examined the extraction efficiencies of three additional new solvent mixtures (dimethyl sulphoxide:acetonitrile:water, 5:58:37 (v/v/v); dimethyl sulphoxide:ethanol:water, 5:70:25 (v/v/v); Genapol:water 5:95 (v/v) for the extraction of isoflavones from soybeans. Assessments of six commonly used extraction techniques (shaking, vortexing, sonication, stirring, Soxhlet, and pressurized liquid extraction (PLE)) with an optimized extraction solvent mixture was also performed. Both, the total isoflavones content and the isoflavones HPLC profile varied significantly with different extraction solvents and techniques. Optimum total isoflavones recoveries from soybean samples were obtained with dimethyl sulphoxide:ethanol:water (5:75:25, v/v/v) solvent mixture using a PLE. Intermediate extraction recoveries of total isoflavones from soybean samples were obtained with the other extraction solvent mixtures and techniques tested. The extraction efficiencies of isoflavones with shaker, vortex, stirring, and Soxhlet were between 65 – 70 % as compared to PLE. Total isoflavones extracted by the sonication procedure was 93.3 % as compared to PLE.