Source, Etc

The official quassiawood is derived from Picroena excelsa, Lindley (N.O. Simarubeoe), a tree of moderate size, common on the plains and lower mountains of Jamaica.

Quassia wood was introduced into medicine about the middle of the eighteenth century, but was then obtained from Quassia amara, Linne, a smaller tree than Picroena excelsa, and indigenous to the north of South America, whence its usual, distinctive name of Surinam quassia. The wood of P. excelsa was found to possess the same properties, and has been substituted for it in England, but Surinam quassia remains official on the Continent.

The trunks and larger branches with the bark attached are exported in logs and billets about 1 1/2 to 2 metres in length and 20 to 30 cm. in diameter.

Description

The logs of Jamaica quassia wood are commonly covered with a thin, dark grey or nearly black bark. The wood is pale yellow in colour, light, rather dense, and easily split. When the smoothed transverse section is moistened and examined with a lens numerous, narrow medullary rays can be seen traversing somewhat irregular concentric rings. The latter are not annual rings, but are produced by the distribution, in more or less concentric zones, of bands of parenchyma (false annual rings). The vessels are usually in groups of two or three, and frequently extend from one medullary ray to the next.

Not unfrequently dark grey patches are visible in the wood; they are caused by a fungus, the dark hyphae of which penetrate the wood through the cells of the medullary rays and wood parenchyma.

The wood has no odour, but the taste is purely and intensely bitter. For use in pharmacy it is usually cut across the grain by large knives like chisels and the chips kiln-dried to prevent them becoming mouldy, as the wood often contains much moisture.

The student should observe

(a) The pale colour and intensely bitter taste of the drug,

(b) The distribution of the vessels.

Constituents

According to Massute (1890), Jamaica quassia wood contains two closely allied crystalline bitter principles, a-picrasmin, C35H46O10 (m.pt. 204°), and β-picrasmin, C36H48O10

(m.pt. 209° to 212°), which are to be regarded as the active constituents; it contains, further, a very small amount of a crystalline bitter principle melting at 234°, as well as a minute quantity of a yellow crystalline substance which exhibits in acidified alcohol a magnificent blue fluorescence. It contains no tannin.

Use

Quassia is used as a pure bitter tonic. It is also largely used for the preparation of horticultural insecticides and non-poisonous fly papers. Cups turned from the wood were formerly in use under the name of bitter cups.

Substitutes

Surinam quassia is usually in smaller billets than Jamaica quassia; it is best distinguished by its microscopical characters, most of the medullary rays being one cell wide, whereas in Jamaica quassia they are two or three cells wide; the wood parenchyma is free from crystals of calcium oxalate, which are contained in Jamaica quassia. The width of the medullary rays and the presence of calcium oxalate are therefore specified in the Pharmacopoeia in order to exclude Surinam quassia; for although the physiological action is presumably the same, it is desirable for the sake of uniformity to use one variety of the wood only. The bitter principles contained in Surinam quassia are distinct from those of Jamaica quassia, and have been called 'quassiins' (Massute, 1890).

Quassia chips that have been exhausted and re-dried yield less aqueous extract (2.7 as compared with 6.3 to 8.6 from genuine wood) and are less bitter.