This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
This plant is a climbing shrub indigenous to the Malay Archipelago and largely cultivated on the small islands between Singapore and Sumatra, as well as in British North Borneo, and on other islands of the Archipelago. The drug was introduced into Europe towards the end of the eighteenth century, but was probably used in India at much earlier times for chewing with betel leaf (the leaf of Piper Betle, Linne).
The leaves and young shoots of the shrub are collected and boiled with water; the decoction is evaporated to a syrup in copper pans (iron pans would discolour it) and cooled; during the cooling the workman works a stick up and down in an oblique direction in the liquor, by which crystallisation is induced and a mass of the consistence of soft clay is obtained. This is usually conveyed in a moist state, often dripping with the mother liquor that drains from the crystalline mass, to Singapore, where it is cut into cubes from 2 to 3 cm. in diameter and dried. Occasionally it is formed into strips, plates, or small round discs, or sometimes it is imported in large blocks, but cube gambier is the form in which it is usually employed in pharmacy.
Gambier, as observed, is usually seen in the form of tolerably regular cubes, measuring from 2 to 3 cm. each way; it is light in weight, and of a. dull, dark reddish brown colour externally, which, however, varies slightly, even on different sides of the same piece. The cubes break easily, and internally are of a pale cinnamon-brown colour, porous and friable. The drug has no odour; the taste is at first bitter and astringent but afterwards sweetish.
Gambier of good quality is almost entirely soluble in boiling water, and yields not less than 80 per cent, to alcohol.
The filtrate from the alcoholic solution, made strongly alkaline with solution of potash and shaken with petroleum spirit, imparts to the latter a brilliant green fluorescence, a reaction which is characteristic of gambier.
A little of the powdered drug mounted in water and examined under the microscope exhibits numerous minute acicular crystals (of catechin), but should be free from starch. The residue left after extraction with alcohol may also be tested for starch. The ash should not exceed 5 per cent.
Gambier consists principally of catechin and catechutannic acid, these two substances in varying proportions constituting together in good specimens over 60 per cent, of the drug; the percentage of catechin varies from 7 to 33 per cent., that of catechutannic acid from 22 to 50. These figures, however, vary with the care with which the drug has been prepared. Brown substances, rubinic and japonic acids, of unknown chemical nature are also present.
Catechin, C15H1406,4H10, forms white, silky, acicular crystals with an astringent taste; it is sparingly soluble in cold but freely in boiling water, the solution giving an intense green colour with ferric salts. In the presence of caustic alkalies and water, catechin readily absorbs oxygen and yields a black dye; with carbonated alkalies the colour is red. Cotton may be dyed brown by steeping in a hot solution of gambier containing a little copper sulphate and then immersing it in a hot solution of potassium dichromate; the catechin is probably first converted into catechu tannic acid and then oxidised to japonic acid. Gambier also contains small quantities of a second catechin, C15H1406, differing from the foregoing in its melting point and crystalline form.
Catechutannic acid has been obtained as a reddish, amorphous substance easily soluble in cold water and in alcohol, the former being used to extract it from the drug. It is apparently produced from catechin by loss of a molecule of water, and itself yields an insoluble red substance, catechu-red, when boiled with water or with dilute mineral acids. These three substances, catechin, catechutannic acid, and catechu-red, appear therefore to stand in close relation to one another, and the relative proportion in which they occur in the drug depends largely upon the care with which it is manufactured, well-prepared gambier containing most catechin. Hence commercial gambier may contain as much as 50 per cent, of catechutannic acid, and as little as 7 per cent, of catechin.
Trimble (1888) found in three samples of gambier the following composition: -
Ash . . . .
Colouring matter, etc........
Other investigators have obtained larger proportions both of catechin (up to 33 per cent.) and catechutannic acid (up to 50 per cent.).
Other constituents of the drug are catechu-red, quercetin, and gambier-fluorescin, a fluorescent substance which can be removed from an alkaline solution of gambier by shaking with petroleum spirit. This fluorescent substance is absent from black catechu and many similar extracts, and forms therefore a valuable means of identifying gambier (Dieterich, 1897).
Gambier is employed medicinally as a local astringent in the form of a lozenge or as a general astringent in diarrhoea; its use for these purposes is, however, insignificant compared with the quantities consumed in the dyeing and tanning industries; for the former, a mixture of catechin and catechutannic acid is said to give the best results.