Rapid analysis of polymethoxylated flavones from citrus oils by supercritical fluid chromatography

The analysis of citrus essential oils for their content of polymethoxylated flavones (PMFs) using packed column supercritical fluid chromatography (SFC) is described. Samples of sweet orange and mandarin oil were quantitatively analyzed and the resulting flavone levels compared to the values obtained using liquid chromatography. In addition, milligram quantities of all six individual flavone compounds were isolated from a sample of sweet orange oil. Flavone retention in SFC is explained on the basis of substituent dipolarity. Dipoles were calculated using molecular modeling techniques, and the effects of substituent positions or neighboring dipoles were investigated. It is postulated that steric hindrance plays a role in the retention mechanism.