Botanical Origin—The trees from which this drug is manufactured are of two species, namely:—

1. Acacia Catechu Willd. (Mimosa Catechu L. fil., M. Sundra Roxb.[923]), a tree 30 to 40 feet high, with a short, not very straight trunk4 to 6 feet in girth, straggling thorny branches, light feathery foliage, and dark grey or brown bark, reddish and fibrous internally.

It is common in most parts of India and Burma, where it is highly valued for its wood, which is used for posts and for various domestic purposes, as well as for making catechu and charcoal, while the astringent bark serves for tanning. It also grows in the hotter and drier parts of Ceylon. A. Catechu abounds in the forests of Tropical Eastern Africa; it is found in the Soudan, Sennaar, Abyssinia, the Noer country, and Mozambique, but in none of these regions is any astringent extract manufactured from its wood.

2. A. Suma Kurz[924] (Mimosa Suma Roxb.), a large tree with a red heartwood, but a white bark, nearly related to the preceding but not having so extensive a geographical range. It grows in the South of India (Mysore), Bengal and Gujerat. The bark is used in tanning, and catechu is made from the heartwood.

The extract of the wood of these two species of Acacia is Catechu in the true and original sense of the word, a substance not to be confounded with Gambier, which, though very similar in composition, is widely diverse in botanical origin, and always regarded in commerce as a distinct article.

History—Barbosa in his description of the East Indies in 1514[925] mentions a drug called Cacho as an article of export from Cambay to Malacca. This is the name for Catechu in some of the languages of Southern India.[926]

About fifty years later, Garcia de Orta gave a particular account of the same drug[927] under its Hindustani name of Kat, first describing the tree and then the method of preparing an extract from its wood. This latter substance was at that period made up with the flour of a cereal (Eleusine coracana Gärtn.) into tablets or lozenges, and apparently not sold in its simple state: compositions of this kind are still met with in India. In the time of Garcia de Orta the drug was an important article of traffic to Malacca and China, as well as to Arabia and Persia.

Notwithstanding these accounts, catechu remained unknown in Europe until the 17th century, when it began to be brought from Japan, or at least said to be exported from that country. It was known about 1641 to Johannes Schröder,[928] and is quoted at nearly the same time in several tariffs of German towns, being included in the samples of mineral origin.[929]

In 1671, catechu was noticed as a useful medicine by G. W. Wedel of Jena,[930] who also called attention to the diversity of opinion as to its mineral or vegetable nature. Schröck[931] in 1677 combated the notion of its mineral origin, and gave reasons for considering it a vegetable substance. A few years later, Cleyer,[932] who had a personal knowledge of China, pointed out the enormous consumption of catechu for mastication in the East,—that it is imported into Japan,—that the best comes from Pegu, but some also from Surat, Malabar, Bengal, and Ceylon.

Catechu was received into the London Pharmacopœia of 1721, but was even then placed among “Terræ medicamentosæ.”

The wholesale price in London in 1776 was £16 16s. per cwt.; in 1780 £20; in 1793 £14 14s., from which it is easy to infer that the consumption could only have been very small.[933]

Manufacture—Cutch, commonly called in India Kát or Kut, is an aqueous extract made from the wood of the tree. The process for preparing it varies slightly in different districts.

The tree is reckoned to be of proper age when its trunk is about a foot in diameter. It is then cut down, and the whole of the woody part, with the exception of the smaller branches and the bark, is chopped into chips. Some accounts state that only the darker heartwood is thus used. The chips are then placed with water in earthen jars, a series of which is arranged over a mud-built fireplace, usually in the open air. Here the water is made to boil, the liquor as it becomes thick and strong being decanted into another vessel, in which the evaporation is continued until the extract is sufficiently inspissated, when it is poured into moulds made of clay, or of leaves pinned together in the shape of cups, or in some districts on to a mat covered with the ashes of cow-dung, the drying in each case being completed by exposure to the sun and air. The product is a dark brown extract, which is the usual form in which cutch is known in Europe.

In Kumaon in the north of India,[934] a slight modification of the process affords a drug of very different appearance. Instead of evaporating the decoction to the condition of an extract, the inspissation is stopped at a certain point and the liquor allowed to cool, “coagulate,” and crystallize over twigs and leaves thrown into the pots for the purpose. How this drug is finished off we do not exactly know, but we are told that by this process there is obtained from each pot about 2 lb. of “Kath” or catechu, of an ashy whitish appearance, which is quite in accordance with the specimens we have received and of which we shall speak further on.

In Burma the manufacture and export of cutch form, next to the sale of timber, the most important item of forest revenue. According to a report by the Commissioner of the Prome Division, the trade returns of 1869-70 show that the quantity of cutch exported from the province during the year was 10,782 tons, valued at £193,602, of which nearly one-half was the produce of manufactories situated in the British territory. Vast quantities of the wood are consumed as fuel, especially for the steamers on the Irrawadi.[935]

Description—Cutch is imported in mats, bags, or boxes. It is a dark brown, extractiform substance, hard and brittle on the surface of the mass, but soft and tenacious within, at least when newly imported. The large leaf of Dipterocarpus tuberculatus Roxb., the Ein or Engben of the Burmese, is often placed outside the blocks of extract.

Cutch when dry breaks easily, showing a shining but bubbly and slightly granular fracture. When it is soft and is pulled out into a thin film, it is seen to be translucent, granular and of a bright orange-brown. When further moistened and examined under the microscope, it exhibits an abundance of minute acicular crystals, precisely as seen in gambier. We have observed the same in numerous samples of the dry drug when rendered pulpy by the addition of water, or moistened with glycerin and viewed by polarized light.

The pale cutch referred to as manufactured in the north of India, is in the form of irregular fragments of a cake an inch or more thick, which has a laminated structure and appears to have been deposited in a round-bottomed vessel. It is a porous, opaque, earthly-looking substance of a pale pinkish-brown, light, and easily broken. Under the microscope it is seen to be a mass of needle-shaped crystals exactly like gambier, with which in all essential points it corresponds. We have received from India the same kind of cutch made into little round cakes like lozenges, with apparently no addition. The taste of cutch is astringent, followed by a sensation of sweetness by no means disagreeable.

Chemical Composition—Extractiform cutch, such as that of Pegu, which is the only sort common in Europe, when immersed in cold water turns whitish, softens and disintegrates, a small proportion of it dissolving and forming a deep brown solution. The insoluble part is Catechin in minute acicular crystals. If a little of the thick chocolate-like liquid made by macerating cutch in water, is heated to the boiling point, it is rendered quite transparent (mechanical impurities being absent), but becomes turbid on cooling. Ferric chloride forms with this solution a dark green precipitate, immediately changing to purple if common water or a trace of free alkali be used.

Ether extracts from cutch, catechin. This substance has been investigated by many chemists, but as yet with discrepant results. It agrees, according to Etti (1877), with the formula C₁₉H₁₈O₈, when dried at 80° C. By gently heating catechin, Catechu-tannic acid, C₃₈H₃₄O₁₅, is produced:

2(C₁₉H₁₈O₈)-OH₂ = C₃₆H₃₄O₁₅.

This is an undoubted acid, readily soluble in water, of decidedly tanning properties, precipitating also the alkaloids and albumin. Catechu-tannic acid being the first anhydride of catechin, there are several more substances of that class; one of them is called Catechuretin. This blackish brown almost insoluble substance is obtained by heating catechin with concentrated hydrochloric acid at 180°:

2(C₁₉H₁₈O₈)-4 OH₂ = C₃₈H₂₈O₁₂.

Catechin, by melting it with caustic potash, affords Protocatechuic acid, C₆H₃(OH)₂COOH, and Phloroglucin, C₆H₃(OH)₃:

C₁₉H₁₈O₈ + 2 OH₂ = 4 H · C₇H₆O₄ · 2 C₆H₆O₃.

Gautier (1877) also obtained the two latter products, but he is of the opinion that they are due to a somewhat different reaction, the formula of catechin, as derived from his analyses, being C₂₁H₁₈O₈. He also asserts that the so-called catechin from Uncaria (see Gambier) is not identical with the substance under notice, nor with that found in the Mahogan wood, to which Gautier assigns the formula C₄₂H₃₄O₁₆.

Crystallized deposits of catechin are sometimes met with in fissures of the trunk of Acacia Catechu, and used medicinally in India under the name Keersal.[936]

Löwe (1873), by exhausting cutch with cold water and then agitating the solution with ether, obtained upon the evaporation of the latter a yellow crystalline substance which he ascertained to be Quercetin, C₂₇H₁₈O₁₂. Its solubility in water is probably favoured by the presence of catechin, water having but very little action upon pure quercetin. The amount of quercetin in cutch is exceedingly small.

When either cutch or gambier is subjected to dry distillation it yields, in common with many other substances, Pyrocatechin, C₆H₄(OH)₂.

Commerce—The importations of cutch into the United Kingdom from British India (excluding the Straits Settlements and Ceylon) were as under, almost the whole being from Bengal and Burma:—

The total value of the cutch imported in 1872 was estimated at £124,458.

Uses—Cutch under the name of Catechu, which name it shares with gambier, is employed in medicine as an astringent.

Analogous Products—See our articles Semen Arecæ and Gambier.