This section is from the book "Materia Medica And Therapeutics - Vegetable Kingdom", by Charles D. F. Phillips. Also available from Amazon: Materia Medica And Therapeutics: Vegetable Kingdom.
Active Ingredients. - The ingredients which confer physiological and therapeutic power upon the cinchona barks are very numerous. They may be divided into four groups, varying in importance, but perfectly well distinguished from one another, and, excepting the last, these are again resolvable into smaller groups. The primary ones are as follows: (1) Alkaloids; (2) Simple Acids; (3) Tannins; (4) the resinoid Kinovine.
1. Alkaloids. - These are resolvable into (a) Quinine; (b) Cincho-nine; (c) Quinidine; (d) Cinchonidine; (e) Aricine. There is likewise the so-called Quinoidine, an impure residue of manufacture from which is prepared the amorphous quinine of Liebig.
(a) Quinine, C20H14N2O2, exists in all the medicinal cinchonas, but is most plentiful in "yellow bark," occurring in natural combination with kinic acid and kino-tannic acid. The pure alkaloid is a strong base. It completely neutralizes acids, and produces with them both neutral salts and acid salts which are crystalline. It is very insoluble in water, freely soluble in alcohol, and less so in ether.1 The solutions are distinguished by a remarkable blue fluorescence. Excess of chlorine-water, and the subsequent addition of ammonia, produce with the salts an emerald green. Quinine per se, is never employed in medicine. By far the most commonly used salt is the neutral sulphate (2C20H14N2O4,HO,SO3 + 7HO), which substance crystallizes in tufts of fine silky needles, and occasionally scales. These are so light that the aggregate of the mass occupies considerable space. In ordinary states of the atmosphere and of storage, the sulphate contains at least two equivalents of extraneous water, which can be entirely driven off by a temperature of 248 ° F., but speedily becomes reabsorbed. The purely bitter taste of quinine is highly characteristic.
Of late years, however, and especially in Germany, the neutral hy-drochlorate of quinine has been preferred by many physicians, particularly by Binz, not only on account of its superior medicinal qualities, but because it is less subject to the fungus which spoils ordinary quinine solutions.
Numerous other salts of quinine will be mentioned under the head of
1 The hydrate, with three equivalents of water, is much more soluble in ether than the anhydrous alkaloid.
Preparations. Here it will suffice to state that the sulphate and the hy-drochlorate are probably capable of accomplishing all the good that can certainly be effected by quinine.
(b) Cinchonine, C20H14N2O, is most abundant in the paler varieties of bark. It forms clear, colorless, four-sided prisms, which are soluble in thirty parts of water, and are very insoluble in alcohol and in ether. With acids it forms soluble salts, which do not fluoresce in solution, and are turned lightish brown-yellow by the chlorine and ammonia tests.
(c) Quinidine, C20H14N2O2, contained in many varieties of bark, is an alkaloid isomeric with quinine, with two equivalents of water, but is less intensely bitter, and less soluble in water and in ether. It gives a similar fluorescence, and the same color with the chlorine and ammonia tests. Sulphate of quinidine is much more soluble in water than sulphate of quinine.
(d) Cinchonidine, C20H14N2O, is isomeric with cinchonine. It occurs in large, shining, striated, rhombic prisms, which are anhydrous, and scarcely at all soluble in ether. The solutions are fluorescent, but do not answer to the chlorine and ammonia tests. In taste, compared with quinine, it is less bitter.
(e) Aricine, C23H16N2O4. Concerning this it is unnecessary to say anything in detail, since there is no probability of its ever being brought into use in practical medicine.
2. Simple Acids. - The simple acids contained in the cinchona barks are the Kinic and the Kinovic.
(a) Kinic acid (or Quinic acid), C7H12O8, forms large, transparent, colorless tablets, the taste of which is strongly and purely acid. They dissolve very easily in cold water; much less readily in boiling water. They are more soluble in weak than in strong alcohol, and in ether are nearly insoluble.
(b) Kinovic acid, C24H38O4, was for a long time supposed to be obtainable only by artificial (chemical) means from the resinoid Kinovine. It is now known to be a natural ingredient of the raw kinovine, or at all events of the kinovine which is furnished by the cinchonas grown in Java. This acid is probably of far greater importance than the kinic; recent researches, as will be shown presently, have invested it with much interest.
3. Tannin. - The tannic acids of the cinchonas are two: (a) Kino-tannic acid, and (b) Kinovi-tannic acid.
(a) Kino-tannic acid, as prepared by Schwarz's process, is a bright yellow mass, easily pulverized, but very hygroscopic, and possessed of a sour and astringent, but not bitter taste. Friction renders it electrical. It dissolves readily in water, alcohol, and ether. (Formula, C24H30O35?)
(b) Kinovi-tannic acid is of a clear, transparent, yellow color, and in taste is somewhat bitter. It is soluble in water and in alcohol, but not soluble in ether.
Whether either of these two tannic acids exists in the officinal cinchonas is, however, somewhat doubtful.
4. Kinovine (or Quinovine), C30H48O8, is an amorphous resinoid body, which can be rubbed into a smooth white powder, possessed of manifestly electric properties. When warmed, it evolves a feebly balsamic odor. The taste, though very slight, is sharp, and unpleasantly bitter. The reaction is neutral; it is excessively hygroscopic; hardly at all soluble in water, very soluble in spirit, somewhat less so in ether. Dry distillation with lime develops metacetone and resinoid bodies. Heating with strono-nitric acid causes the evolution of red fumes. Concentrated sulphuric acid gradually dissolves it with a dark red color. Hydrochloric acid vapor conducted into an alcoholic solution causes, as above stated, the development of kinovic acid along with kinova sugar.