The increment of the rate constant (nB) of the process factors
is in the order: the pressure > the temperature > the liquid–solid
ratio > the ethanol concentration. Thus, the pressure has remarkable
effects on the extraction rate. The reason is that the pressure
can induce the rupture of the cellular wall of plant material,
which can allow the solvent to penetrate easily into the plant cell
and the active ingredient to transfer conveniently into the solvent
through the gap and cranny of the cellular wall. Increasing temperature
favors the extraction process by enhancing solubility of
rutin and speeding molecular motion, which can increase the diffusion
rate and reduced the extraction time [31]. A faster extraction
rate was obtained with higher liquid–solid ratio. The driving
force during mass transfer within the cell is considered to be the
concentration gradient, which was greater when a higher liquid–
solid ratio is used, resulting in an increase of the diffusion rate
[34].