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.
Guarana is prepared from the seeds of Paullinia Cupdna, Humboldt, Bonpland, and Kunth (N.O. Sapindaceoe), an elegant climbing shrub indigenous to and common in Brazil, especially in the basins of the Amazon and its tributaries. It derives its name from the Guarinis, an aboriginal tribe of Indians. The difficulty of collecting the seeds from the wild plants, which, though common, are not easily accessible, has apparently led to their cultivation, the plants being trained to poles like hops. When the pods open to discharge the ripe seeds they are collected, and the seeds, which resemble small horse-chestnuts in shape and colour, are separated by shelling. They are first washed and then roasted to loosen them from a papery shell, from which they are freed by beating. The broken kernels are made into a dough with water; this is then divided into masses of varying size and shape, sometimes representing a fish or other animal, which are finally dried at a gentle heat by means of a slow fire. From the hard mass thus obtained portions are grated off with a large file and served in glasses of water, forming a refreshing drink.
Guarana commonly appears on the market in the form of extremely hard, heavy, sausage-shaped masses, varying from 10 to 30 cm. in length and from 2.5 to 4 cm. in thickness. The outer surface is dark chocolate brown in colour, and would be smooth and uniform were it not that small angular fragments, often of lighter colour than the rest, project slightly; these fragments are evidently the larger pieces of the broken seed. The fractured surface, smoothed with a knife, is reddish in colour, and exhibits, like the outer surface, small paler irregular fragments embedded in a darker reddish mass, but no definite structure is discernible. The powder, in which form the drug is administered, is of a pale red colour; it has a scarcely perceptible Odour and slightly astringent, bitter taste.
The student should observe
(a) The extremely hard heavy masses in which the drug occurs,
(b) The presence of small, paler fragments embedded in them.
The detection of foreign substances in such a drug as guarana is attended with considerable difficulty. The amount of caffeine should not be less than 2.5 per cent. Microscopical examination has shown the presence of the seed-coats, which therefore are only imperfectly separated, and frequently of foreign starches; the latter, according to Schar (1897), are regularly present. Thorns (1894) found in guarana 8.63 per cent, of moisture, 1.68 per cent, of ash, and 2.68 per cent, of caffeine, the seeds themselves yielding closely concordant figures.
Guarana is employed as a nervine stimulant in the same way that tea and coffee are, and produces similar effects. It has been long in common use in Brazil.