Because of the structure diversity of alkaloids, there is no single method
of their extraction from nature raw materials. Most methods exploit the property
of most alkaloids to be soluble in organic solvents but not water. Most alkaloids
are present in the raw plants in the form of salt of organic acids. Usually
inorganic acidic extraction is used, so that the organic acid of alkaloids salt is
replaced inorganic acid salt, and increasing its solubility. The advantage of
acidic extraction is changing alkaloids molecules into small molecular organic
acid salts, increasing the solubility in water, Each monomer of alkaloids often
has different alkaline, we can use the pH gradient extraction to separate. For
example, separating A and D agent from the bark that is using their different
alkaline, have the concentrated solution basified to leach in pH9-10. A agent
was extracted of its low alkaline but B agent whose pH is higher than A agent.
Precipitation method separate water-soluble impurities which remaining in the
filtrate, in order to obtain higher purity water-soluble alkaloids or salts.