The
swelling of Morinda sp. root cells also increased
the surface area and facilitated the extraction
efficiency by the solvents. In addition, the elevated
mass transfer coefficient due to the decreased
ethanol viscosity in the presence of water for up
to 50% could all play parts in optimal extraction
at such situation. The significant role of acetone
in boosting the effect of anthraquinone extraction
efficiency could be explained in term of higher
mass transfer coefficient that allowed the better
access of acetone to the anthraquinone reserve in
each cell of Morinda sp. Furthermore, the
similarity of carbonyl functional group (C=0) in
acetone to that of anthraquinone might also play
part in the improvement of anthraquinone
extraction efficiency (Hemwimol et al., 2006).