Catechu

Catechu, or Cutch, an astringent extract largely employed in tanning and dyeing and to some extent in medicine, which is prepared from several plants. Ordinary black catechu, Pegu cutch, or, as it was long ago named in European pharmacy, when its origin was unknown, terra japonica, is prepared in India from the dark red heart-wood of Acacia Catechu, a small spinous tree, and that of A. Suma, by boiling and evaporation. It is dark brown, almost black, shining and brittle. The pale catechu, Catechu pallidum of pharmacy, or gambier of general commerce, is prepared from the leaves of Uncaria Gambir and U. acida, rubiaceous plants of the Straits Settlements and adjoining states. It is pale brown or yellow, less lustrous and more earthy in its fracture. Catechu is soluble in boiling water, and consists chemically of a mixture of the more soluble amorphous catechu-tannic acid, the less soluble white needle-like crystals of catechin or catechuic acid, and a brown colouring substance. In dyeing, catechu yields various drabs and browns with different mordants, and in tanning it is mainly used for canvas, fishing-nets, and very inferior leather. Great Britain imports several thousand tons of catechu annually from Bengal, and a considerably larger quantity of gambier from Singapore. A substance chemically distinct and but little used in Europe is the kassu, a dark-brown glossy extract from the seeds of Arcca Catechu, the Betel palm. The pharmacopoeial preparations of catechu are an infusion, tincture, lozenges (trochisci), and compound powder (pulvis catechu compositus). They contain an astringent principle allied to tannic acid. The powder and tincture are very useful in certain forms of diarrhoea. The lozenges are useful in relaxed sore throat.