This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
The bark of the root of Berberis vulgaris is the part designated in the U. S. Pharmacopoeia as officinal. The plant is a shrub, sometimes attaining the size of a small tree, indigenous in Europe, but growing wild in various parts of our own country, as in New England and on the banks of the Hudson. A species of the genus, designated by Pursh as Berberis Canadensis, grows in our country from its northern boundaries to the Carolinas. Hooker, however, considers it as merely a variety of B. vulgaris; and, whatever may be the fact on this point, there can be little doubt that it possesses the same medical virtues.
The bark of the root is grayish on the outer, and yellow on the inner surface; is very bitter, staining the saliva yellow when chewed; and yields its virtues and colouring properties to water and alcohol. Long employed in medicine, it never enjoyed a very high reputation, and seems to have fallen into almost entire neglect; but, when it was ascertained to contain a peculiar alkaloid, and that alkaloid found to be diffused among various other medicines, some of them very greatly esteemed, as columbo, xanthorrhiza, xanthoxylum, hydrastis, etc., attention was again forcibly drawn to it, with the result of introducing it into the present edition of our Pharmacopoeia, though in the secondary catalogue. For the method of extracting berberina from the bark, I must refer to the U. S. Dispensatory (12th ed., p. 168). Of the alkaloid itself, the most important and characteristic properties may be given in a few words. When obtained by crystallization from the hot solution, resulting from the decomposition of its sulphate by means of oxide of lead, added to a heated solution of that salt, it is in the form of a yellow powder, shown by the microscope to consist of groups of minute acicular crystals. It is inodorous, bitter, soluble in 100 parts of cold water, and requiring still more of cold alcohol, but freely dissolved by both these liquids with the aid of heat, and insoluble in ether. Its most characteristic property is probably that of being copiously precipitated by muriatic acid from its solution in cold water, owing to the very difficult solubility of the resulting muriate. This property, taken in connection with the bright-yellow colour of the muriate, is sufficient to distinguish berberina from ail other alkaloids. Notwithstanding the very difficult solubility of the muriate in cold water, yet enough is dissolved to produce a deep-yellow colour. Another alkaloid has also been found in the root for which the name of vinetina has been proposed. But little is known of its physiological properties. Both alkaloids consist of carbon. hydrogen, nitrogen and oxygen; but their precise atomic composition can scarcely be said to have been yet determined, though that of berberina has been given as C40H17No8' of vinetina C32H20No11.
Barberry is tonic, and when freely given, cathartic, with a supposed action on the liver. It has been used in intermittent fever, dyspeptic affections with constipation, and in jaundice. Whether it has any real influence on the liver is not vet determined, and would form a good subject for careful inquiry. It was probably first introduced into the treatment of jaundice on the doctrine of signatures, which implies a certain relation between the sensible properties of the medicine and those of the part diseased, or some product of the disease; as, in this case, between the yellowness of the bark and that of bile. But, baseless as this principle is, some medicines introduced into use on the grounds of it, have retained their place from their real virtues; and the same may possibly be the case with barberry.
The substances which follow, belonging to the subdivision of bitter tonics of peculiar properties, owe their peculiarity in general to the association of some other active constituent with their bitter principle. This associated constituent is, with one or two exceptions, a stimulant volatile oil. The most decided exception to this general rule is afforded by the wild-cherry bark, in which, though a somewhat stimulating volatile oil is always generated when it is exposed to the action of water, whether within the stomach or out of it, yet, in connection with this oil, a powerful sedative is also produced, hydrocyanic acid, namely, to which the medicine is mainly indebted for its peculiar and characteristic effects.