Homoquinine is decomposed on treatment with caustic soda into quinine and a new alkaloid, cupreine, in the proportion of 2 to 3.
Cupreine is soluble in a solution of caustic soda (differing in this respect from quinine), and therefore it is easy to prepare sulphate of quinine perfectly free from either homoquinine or cupreine.
The medicinal properties of cupreine and homoquinine are of no practical importance.
Thus quinine is methoxycinchonine or methylcupreine, cupreine being an oxycinchonine.
OH; cupreine = C19H20N2(OH)21 quinine =C19H20N2(OH) (OCH 3).