Effective extraction of tocopherols from soybean oil deodorizer distillate methyl esters using phenolic deep eutectic solvents

Nature tocopherols are mainly produced from vegetable oil deodorized distillates. And development of simple and green extraction method is highly desirable for nature tocopherols separation. In this work, a green, rapid and mild (room temperature) solvent extraction method based on phenolic deep eutectic solvents (DES) has been developed to simultaneously extract three isomers of tocopherols (α-, γ-, δ-tocopherol) from soybean oil deodorizer distillate methyl esters (SODD-ME) for the first time. Tetrabutyl ammonium chloride-based DESs (TBAC-DESs) were used as extraction solvents. The effect of factors on the extraction efficiency of three individuals and total tocopherols was investigated. The optimal extraction conditions were determined as follows: DES composed of TBAC and 4-methylphenol (molar ratio of 1:1), DES/SODD-ME 6:1 (w/w), hexane/SODD-ME 1:1 (w/w) and vortex-assisted extraction of 1 min at room temperature. Under these conditions, the maximum extraction efficiency of total tocopherols was (97.5 ± 0.5)%. And the molecular structure of the phenolic DESs had significant effect on the extraction selectivity on α-, γ- and δ- tocopherol from SODD-ME. The underlying extraction mechanism was that the TBAC-phenol DESs combined the three tocopherols by both hydrogen bonding and π-π interaction.