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.
Eucalyptus Kino, or as it is commonly termed ' red gum,' is a variety of Australian kino obtained from Eucalyptus rostrata, Schlechtendal (N.O. Myrtaceoe), and other species (E. marginata, Smith, E. amygdalina, Labillardier, &c). They are all Australian trees, E. rostrata forming large forests on the banks of the Murray River in New South Wales and yielding a valuable timber. This species is usually preferred as the source of red gum for medicinal use, because the tree is gregarious, cannot easily be mistaken for others, and yields freely a drug of good quality. The gum, which is secreted in cavities in the wood, or sometimes between the bark and the trunk of the tree, forming carbuncles, is obtained by making an incision and inserting a trough-shaped piece of tin by which the treacly liquid as it drains from the cut is carried into buckets or tins. In a few days it dries into a solid mass which soon becomes friable, breaking up into very dark fragments; or it may be evaporated by boiling, and the official drug is probably prepared by this method. The yield of each tree is very variable, the average being about a litre, some yielding none, others as much as 18 litres (Maiden, 1897).
Red gum is seen in commerce in small pieces, about the size of a pea or less. They are of a dark reddish brown colour, opaque, and more or less dusty, but thin laminae are transparent and ruby-red, the powder being pale reddish in colour. It is somewhat tough, and has when chewed an astringent taste, colouring the saliva red and adhering to the teeth. Cold water should dissolve from 80 to 90 per cent. According to Brownscombe (1899) good qualities should yield not less than the latter percentage.
The student should observe
(a) The reddish colour,
(b) The dusty appearance of the drug.
Red gum contains about 47 per cent, of kinotannic acid (Maiden, 1897), which is undoubtedly its principal constituent. There is also present kino-red, a gelatinisable tannin glucoside, cate-chin, pyrocatechin, and about 15 per cent, of moisture, the remainder consisting of substances not at present exactly known. According to Smith (1904), eucalyptus kinos contain two tannins giving with ferric chloride a violet and a green reaction respectively; the former gelatinises readily but the latter does not.
Red gum is not so powerful an astringent as kino, but its action is said to be slower and more prolonged.