Supercritical carbon dioxide extraction of selected medicinal plants--effects of high pressure and added ethanol on yield of extracted substances.

The possibilities and limitations of supercritical fluid extraction of natural products of low, medium and high polarity under very high pressure and with polar modifiers has been investigated. The medicinal herbs marigold (Calendula officinalis), hawthorn (Crataegus sp.) and chamomile (Matricaria recutita) were used as models in this study. Extraction profiles and the spectra of extractable metabolites were recorded following extraction with mixtures of carbon dioxide:ethanol of varying proportions (0-20% ethanol) and at various pressures in the range 300-689 bar. Components were identified by HPLC-PAD-MS or GC-MS and quantified by HPLC or GC as appropriate. Extraction yields under the varying conditions depended to a large extent on the profiles of secondary metabolites present in the three drugs. Whereas the extractability of lipophilic compounds increased substantially at pressures above 300 bar, the yields of polyphenolic and glycosidic compounds remained low even at 689 bar and with 20% modifier in the extraction fluid.