electron microscope, and their micrographs are shown in Fig. 4.
The cellular wall is the main barrier to extract active ingredient
from plant cell [30]. Thus, we have mainly studied how the cellular
wall is changing under high pressure. As can be seen from Fig. 4,
the cellular wall of untreated sample is in an orderly intact state;
the change in the cellular wall of HRE sample is not considerably
different from that of the untreated sample, and only few slight
loosened phenomena happened; while, in the PSE sample, the cellular
wall is found remarkably cracked and became porous floccules
with distorted cell shape. Therefore, the solvent could
easily enter the cell through the gap and cranny of the cellular wall,
contact the solid substances, and move its active ingredient into
the solvent.