The other alkaloids of cinchona bark - quinidine, cinchonidine, and cinchonine - also possess similar properties, but all are much less effective than quinine.
The inactive mixture may be resolved into its active components by fractional crystallization of the cinchonine salt, when the salt of the dextro modification separates first; or the ammonium salt may be fermented by Penicillium glaucum, when the laevo form is destroyed and the dextro form remains untouched; on the other' hand, Saccharomyces ellipsoideus destroys the dextro form, but does not touch the laevo form.
Lepidine(y-methylquinoline) was first obtained by distilling cinchonine with caustic potash.
It has also been shown by Broughton that C. Peruviana, which yields cinchonine but no quinine at a height of 6000 ft., when grown at 7800 ft.
From analyses of the leaves, bark and root, it appears that quinine is present only in small quantities in the leaves, in larger quantity in the stem bark, and increasing in proportion as it approaches the root, where quinine appears to decrease and cinchonine to increase in amount, although the root bark is generally richer in alkaloids than that of the stem.
Cinchoninic acid (quinoline-y-carboxylic acid) is formed when cinchonine is oxidized by nitric acid, or by the oxidation of lepidine.
The other alkaloids are distinguished from quinine thus: quinidine resembles quinine, but is dextro-rotatory, and the iodide is very insoluble in water; the solution of cinchonidine, which is laevo-rotatory, does not give the thalleoquin test, nor fluorescence; cinchonine resembles cinchonidine in these respects, but is dextrorotatory.
The inactive variety may be split into the component active forms by means of its cinchonine salt (G.