Enhancement of the encapsulation and transmembrane permeation of isoflavone-containing red clover extracts in phospholipid-based microemulsions using different extraction processes.

Several isoflavone-enriched red clover extracts (RCE) prepared by using solid- or liquid-phase extraction or a combination of both were studied for their encapsulation into a phospholipid-based microemulsion system. The optimization process with regard to the bioactive ingredient-encapsulated amounts and transmembrane efficiency of various RCE micelles was demonstrated. The results indicated that the encapsulated amounts of isoflavones in RCE-encapsulated microemulsions (ME) of ME-RC5, ME-RC6, and ME-RC7 were increased by >10-fold when compared with that of the raw red clover extracts. Comparison of the permeability coefficient K(p) of the formononetin among the ME-RCs from the in vitro skin permeation study showed that ME-RC5 significantly exhibited the least permeability, whereas ME-RC6 exhibited enhanced permeability after two-stage solid-phase extraction, indicating the potential role of the matrix material as a barrier or enhancer in the transmembrane study.