Source, Etc

Two varieties of rhatany root, commercially distinguished as Para rhatany and Peruvian rhatany, are official; they are derived from two distinct species of Krameria belonging to the natural order Polygaleoe.

1. Peruvian rhatany is the root of K. triandra, Ruiz and Pavon, which grows on the mountain slopes of Peru and Bolivia.

2. Para rhatany is presumably obtained from K. argentea, Martius, a shrubby plant growing in Brazil.

Rhatany root has apparently been used for many years by the Peruvians for cleaning and preserving the teeth. The Spaniards became acquainted with it in Lima and introduced it into Europe.

Description

The root of Peruvian rhatany is large and knotty at its upper extremity, but divides near the crown into several long stout branches, from which again smaller branches proceed. The larger pieces have a dark reddish brown colour and a rugged, scaly bark; the smaller are usually rather brighter and smoother, not exhibiting any conspicuous transverse fissures. The bark, which can easily be separated from the smaller roots, is rather fibrous, but the wood breaks with a splintery fracture. The transverse section exhibits a pale reddish or yellowish wood and a comparatively narrow reddish brown bark occupying about one-fourth of the radius of a root of medium size. The wood is dense, and marked with numerous narrow medullary rays and minute vessels. The drug is quite odourless; the bark has a strongly astringent taste, but the wood is practically tasteless.

Para rhatany is usually imported in long, nearly straight, cylindrical pieces, not often exceeding 15 mm. in thickness. They are well characterised by their dark purplish brown colour, and by the presence of deep transverse cracks at more or less regular intervals in the bark, which in this variety is never rough or scaly, although transversely fissured and longitudinally wrinkled. The transverse section shows a reddish wood and a dark reddish brown bark, which, in this case occupies about one-half the radius of a root of medium size. In respect to odour and taste Para rhatany resembles Peruvian.

Fig. 157. - Peruvian Rhatany root. A, portion of an older root, showing scaly cork; natural size. B, portion of a younger root, natural size.

The student should carefully compare these two roots, and observe in Peruvian rhatany

(a) The reddish brown bark, which is scaly in large pieces, smoother in the smaller, and free from deep transverse cracks,

(b) The proportion of bark to wood as exhibited in the transverse section; in Para rhatany

Fig. 158. - Para Rhatany. Natural size.

(a) The dark purplish brown colour of the bark, which is not scaly, but exhibits deep transverse cracks,

(b) The proportion of the bark to wood in the transverse section, which is greater than in Peruvian rhatany.

Large pieces of Indian sarsaparilla (see p. 340) occasionally bear a considerable resemblance to small pieces of Para rhatany, both in colour and in the presence of transverse cracks; they may be distinguished by their agreeable odour and by the difference in the transverse section.

Constituents

The principal constituent of rhatany root is the tannin (krameria-tannic acid) that it contains. The proportion in which this substance is present has not been satisfactorily determined, but it has been stated to be 8.4 per cent, in the Peruvian root. The Para variety contains about the same quantity, one assay of the root showing rather more, and another rather less tannin than the Peruvian. These analyses, are, however, of comparatively little value, since the proportion of bark, in which alone the tannin resides, varies in different roots of each variety. The Peruvian root appears to contain a much larger amount of substances soluble in absolute alcohol than the Para root does (23.0 per cent, against 12.6 in the Para - Dunwody, 1890), and certainly yields a tincture possessing different properties, that from the Peruvian giving a cloudy and that from the Para a clear mixture with water. Notwithstanding this difference the Pharmacopoeia retains both, since the supply of each is subject to considerable irregularity.

The root contains in addition a dark red phlobaphene, krameria-red, produced by decomposition of the tannin, as well as starch, and about 2 per cent, of inorganic matter.

Uses

Rhatany root is employed solely as an astringent.

Varieties

Several other species of Krameria are known to yield astringent roots, but none are of commercial importance.