A second bitter principle, Chiratin, C₂₆H₄₈O₁₅, may be removed by means of tannic acid, with which it forms an insoluble compound. Chiratin is a neutral, not distinctly crystalline, light yellow, hygroscopic powder, soluble in alcohol, ether and in warm water. By boiling hydrochloric acid, it is decomposed into Chiratogenin, C₁₃H₂₄O₃, and ophelic acid. Chiratogenin is a brownish, amorphous substance, soluble in alcohol but not in water, nor yielding a tannic compound. No sugar is formed in this decomposition.
These results exhibit no analogy to those obtained in the analysis of the European gentians. Finally, Höhn remarked in chiretta a crystallizable, tasteless, yellow substance, but its quantity was so minute that no investigation of it could be made.
The leaves of chiretta, dried at 100° C., afforded 7·5 per cent. of ash; the stems 3·7; salts of potassium and calcium prevailing in both.
Uses—Chiretta is a pure bitter tonic, devoid of aroma and astringency. In intense bitterness it exceeds gentian, Erythræa and other European plants of the same order. It is much valued in India, but is not very extensively used in England, and not at all on the Continent. It is said to be employed when cheap, in place of gentian, to impart flavour to the compositions now sold as Cattle Foods.
Substitutes and Adulteration—Some other species of Ophelia, namely, O. angustifolia Don, O. densifolia Griseb., O. elegans Wight, O. pulchella Don, and O. multiflora Dalz, two or three species of Exacum, besides Andrographis paniculata Wall., are more or less known in the Indian bazaars by the name of Chiretta[1623] and possess to a greater or less degree the bitter tonic properties of that drug. Another Gentianacea, Slevogtia orientalis Griseb., is called Chota Chiretta, i.e. small chiretta. It would exceed due limits were we to describe each of these plants: we have therefore given a somewhat detailed description of the true chiretta, which will suffice for its identification. We have frequently examined the chiretta found in the English market, but have never met with any other than the legitimate sort.[1624] Bentley noticed in 1874 the substitution of Ophelia angustifolia, which he found to be by far less bitter than true chiretta.
CONVOLVULACEÆ.
SCAMMONIUM.
Scammony; F. Scammonée; G. Scammonium.
Botanical Origin—Convolvulus Scammonia L., a twining plant much resembling the common C. arvensis of Europe, but differing from it in being of larger size, and having a stout tap-root. It occurs in waste bushy places in Syria, Asia Minor, Greece, the Greek Islands, extending northward to the Crimea and Southern Russia, but appears to be wanting in Northern Africa, Italy, and in all the western parts of the Mediterranean basin.
History—The dried milky juice of the scammony plant has been known as a medicine from very ancient times. Theophrastus in the 3rd century b.c. was acquainted with it; it was likewise familiar to Dioscorides, Pliny, Celsus, and Rufus of Ephesus, each of whom has given some account of the manner in which it was collected. Scammony used then also to be called Diagrydion, from the Greek word δάκρυ, tear. The mediæval Arabian physicians also knew scammony and the plant from which it is derived. The drug was used in Britain in the 10th and 11th centuries, and would appear to be one of the medicines recommended to King Alfred the Great, by Helias, patriarch of Jerusalem.[1625] It is repeatedly named in the medical writings in use prior to the Norman conquest (a.d. 1066), in one of which directions are given for recognizing the goodness of the drug by the white emulsion it produces when wetted.