Extraction and separation of flavonoids and iridoids from Eucommia ulmoides leaves using choline tryptophan ionic liquid-based aqueous biphasic systems

The choline tryptophan ionic liquid (IL)-based aqueous biphasic system (ABS) was designed and applied to extract and separate flavonoids and iridoids from Eucommia ulmoides leaves. This ABS possessed a unique viscous layer enriching iridoids that can be directly removed at the interface between the IL-rich and salt-rich phases. The extraction yield of total flavonoids was optimized by RSM to obtain a predicted maximum of 2.91% at the IL concentration of 36.73%, liquid to solid ratio of 38, extraction temperature of 44 degrees C and extraction time of 105 min. The determined extraction yield of total flavonoids is 2.78% +/- 0.12% under revised optimization condi-tions. The distribution coefficient K and extraction rate E of total flavonoids in the IL-rich phase reach the maximum of 129% and 98.53% at the K3PO4 content of 26% in the ILABS, respectively. The HPLC analysis shows a high content of rutin in the flavonoids precipitate induced by water as an anti-solvent. Aucubin content reaches 15.19% in the intermediate viscous layer enriching iridoids. Hence, the designed process has the potential to be applied to the separation and enrichment of rutin and aucubin from other industrial crops.

Automated summary

The choline tryptophan ionic liquid-based aqueous biphasic system was used to extract and separate flavonoids and iridoids from Eucommia ulmoides leaves. The system showed a unique feature of a viscous layer that enriched iridoids and could be easily removed. The optimized extraction conditions resulted in a yield of 2.78% +/- 0.12% for total flavonoids. The distribution coefficient and extraction rate of total flavonoids reached maximum values of 129% and 98.53%, respectively, at a K3PO4 content of 26% in the system.