This section is from the book "Materia Medica And Therapeutics: An Introduction to the National Treatment of Disease", by John Mitchell Bruce. Also available from Amazon: The pharmacology and therapeutics of the materia medica.
Cinchonae Flavae Cortex - Yellow-Cinchona Bark. - The bark of Cinchona Calisaya. Collected in Bolivia and southern Peru.
Characters. - In flat pieces, uncoated or deprived of the periderm, rarely in coated quills, from six to eighteen inches long, one to three inches wide, and two to four lines thick, compact and heavy; outer surface brown, marked by broad shallow irregular longitudinal depressions; inner surface tawny-yellow, fibrous; transverse fracture shortly and finely fibrous. Powder cinnamon-brown, somewhat aromatic, persistently bitter.
Cinchonae Pallidae Cortex - Pale - Cinchona Bark. - The bark of Cinchona Condaminea, D.C., vars. Chahuarguera Pavon, and crispa Tafalla. From Loxa.
Characters. - From half a line to a line thick, in single or double quills, from 6 to 15 inches long, 2 to 8 lines in diameter, brittle, easily splitting longitudinally, and breaking with a short transverse fracture; outer surface brown and wrinkled, or grey and speckled with adherent lichens, with or without numerous transverse cracks; inner surface bright orange or cinnamon-brown; powder pale brown, slightly bitter, very astringent.
Cinchonae Rubrae Cortex - Red-Cinchona Bark. - Trip bark of Cinchona succirubra. Collected on the western slopes of Chimborazo.
Characters. - In flat or incurved pieces, less frequently in quills, coated with the periderm, varying in length from a few inches to two feet, from one to three inches wide, and two to six lines thick, compact and heavy; outer surface brown or reddish-brown, rarely white from adherent lichens, rugged or wrinkled longitudinally, frequently warty, and crossed by deep transverse cracks; inner surface redder; fractured surface often approaching to brick-red; transverse fracture finely fibrous; powder red-brown; taste bitter and astringent.
Cinchona Lancifoliae Cortex - Lance-Leaved Cinchona Bark. - The bark of Cinchona lancifolia, Mutis. Spongy or orange Carthagena bark.
Characters. - Either in quills of various size with brownish epidermis, and whitish crustaceous and foliaceous lichens, extremely fibrous, moderately bitter; or as curved pieces, of an orange or red colour, with an extremely fibrous liber, of stringy fracture, very slightly bitter.
Composition. - Cinchona bark contains (1) four alkaloids, namely: quinia, cinchonia, quinidia, and cinchonidia; (2) two peculiar acids: kinic and kinovic acids; (3) a variety of tannic acid, called cincho-tannic acid; (4) cinchona red; and (5) an aromatic volatile oil.
The Alkaloids Of Cinchona. a. Quinia, C20H14N2O2, occurs (as the hydrate) in white acicular crystals, inodorous, very bitter; reacting like an alkali, and forming neutral and acid salts with acids; presenting fluorescence in dilute solutions of the sulphate; and turning the plane of polarisation to the left. An amorphous form of quinia is found after crystallisation of the sulphate from the mother-liquors, and from quinoidia, which appears to be a compound of the alkaloids with resin and colouring matters.
b. Cinchonia, C20H14N2O, consists of colourless prisms, inodorous, and bitter; forms salts with acids; but possesses no fluorescence in solution; and deflects the plane of polarisation to the right.
c. Quinidia, C20H14N2O2, i.e. isomeric with quinia, closely resembles quinia, but crystallises in prisms, and deflects the plane of polarisation to the right.
d. Cinchonidia. C20H14N2O, i.e. isomeric with cinchonia, resembles that alkaloid, but yields fluorescent solutions, and left-handed polarisation.
As a rule quinia is most abundant in yellow bark, cinchonia in pale bark, and the red bark contains a considerable proportion of each. Quinidia is specially abundant in the bark of lancifolia. More exactly, yellow bark yields 2.5 to 3.8 per cent, of quinia; pale bark, 0.7 to 1.4 per cent, of alkaloids, chiefly cinchonia or quinidia with a little quinia; the best red bark, 2.6 per cent, of quinia, and 1.5 per cent. of cinchonia.
2 and 3. The acids of cinchona. - a. Kinic or quinic acid, C7Hl206, occurs in large colourless prisms, soluble in water. In the bark it is probably combined with the alkaloids, and is found also in the coffee-bean, the Vaccinium myrtillus, and other plants. It is closely allied to benzoic acid, and appears in the urine as hippuric acid. See Benzoinum, page 281.
b. Kinovic acid, C24H38O4, "kinova bitter," is a white amorphous "body, insoluble in water. It appears to be a product, with glucose, of kinovin, a glucoside.
c. Cincho-tannic acid, the astringent principle and soluble red-colouring matter of the bark, amounts to 1 to 3 per cent. It is a yellow hygroscopic body, and differs from ordinary tannic acid in striking green with persalts of iron, and in being very readily oxydised, one of the products being 4. Cinchona red, a reddish-brown substance without taste or smell, nearly insoluble in water.
6. The volatile oil, obtained by distillation, has the odour of the bark.
Impurities. - Inferior barks are detected by the absence of the true characters of the officinal barks, and by a quantitative test. This consists in (1) boiling 100 gr. of the bark in water acidulated with HC1, macerating, and percolating; (2) precipi-tating the colouring matter with solution of subacetate of lead; (3) adding caustic potash to the filtrate, until the precipitate first formed is nearly redissolved; (4) agitating with ether, and evaporating the resulting solution. This should yield not less than 2 gr. of quinia from yellow bark; 2 gr. of alkaloids from red bark; and 1/2 gr. of alkaloids from pale bark. The yellow bark is adulterated with elm, larch, and Winter's barks, known by absence of bitter taste; the pale bark with cascarilla, which is whiter; the red bark with red sandal wood, logwood, and larch barks, which are all devoid of a bitter taste.
Incompatibles. - Ammonia, lime-water, metallic salts, and gelatine. May be combined with mineral acids.