Novel isolation of phytochemical compositions by phase transition extraction with acetonitrile

Based on the phenomenon that hydrophilic acetonitrile can be separated from water by adding a hydrophobic solvent, a phase transition extraction (PTE) method for isolation of phytochemical compositions was developed. The isolation efficiency of the proposed method was assessed in complete grouping of the constituents in three important traditional Chinese medicine plants. Further study of the PTE for Scutellaria bacalensis Georgi found that the constituents in the organic phase are all flavonoid aglycones while the ones in the aqueous phase are all flavonoid glycosides, revealing the property of high structure selectivity for the proposed PTE process. The effect of using different modifiers on the isolation efficiency was investigated. The results obtained by using non-oxygenated hydrophobic solvents are perfect while those by inorganic salts are acceptable, but those by oxygenated hydrophobic solvents are bad. Subsequent GC analysis revealed that the solvent composition difference between the two separated phases among PTE processes using different types of modifier is responsible for the different isolation results obtained. Finally, the proposed method was proved to be insensitive to both the acetonitrile concentration and the added amount of modifier.