3.5. Kinetic of destruction of andrographolide
It might seem that raising the temperature would always
be a good way to save time by making reaction go faster.
However, the problem with raising the temperature is that
all reactions are accelerated, including all the unwanted
side reactions. Since andrographolide is a lactone, the opening
of the lactone ring can be the most likely destruction
mechanism. However, the lactone ring would react in different
manner with water and ethanol. The former will open
the ring by hydrolysis, whereas the latter will do it by
trans-esterification. Hydrolysis is expected to be much faster
reaction compared to trans-esterification. Then the rate of
destruction should be depending both on the temperature
and on the composition of the solvent.