Natural amines found in plants are easy to isolate. The extract is first acidified. The amines will form a water-soluble complex which can be separated from the organic medium. Then an alkali is added to reform the amine which is then extract with organic solvents. To the early scientists studying medicinal plants, amines have the properties of an alkali in this aspect. So it is not surprising that pharmacologist W. Meissner proposed that such plant extracts be known as alkaloids (alkali-like compounds).

Many alkaloids are familiar to us because of their physiological properties. The most popular are those with toxic or adductive properties. Below are some of the better known alkaloids.

Morphine: X = HO , Y = HO. Codeine: X = CH3O , Y = HO. Heroin: X = CH3−C(O)O, Y = CH3−C(O)O.