Typically, bioactive compounds in herbal plants are present in
low concentrations. Thus, it is very important to develop more
effective and selective extraction methods for the recovery of the
desired bioactive compounds from the herb materials. Traditional
organic solvent-based extraction often suffers from low extraction
yields, long extraction times, and residual toxic organic solvents
in final products. The residual solvents are problematic because
residual toxic organic solvents in extracts can deteriorate the quality
of the extracts and can cause serious health problems when the
extracts are taken into thehumanbody. Hence, high level of vacuum
under heating, that is a high energy-consuming evaporation process,
is often needed to remove the residual solvents in the extracts
to permitted levels. Supercritical fluid extraction (SFE), especially
supercritical carbon dioxide (scCO2) extraction, of bioactive materials
from herb plants is a potential alternative to conventional liquid
solvent extractions [9]. Themajor disadvantage of scCO2 extraction,
however, is that extraction of polar components is highly limited by
the poor solvent power of scCO2 for the polar components.