Gambier a.k.a catechu, a common ingredient used by Asians in chewing betel nut, is prepared from parts of the shrub Uncaria gambier (Uncaria gambir) of the family Rubiaceae. There are two varieties of catechu: pale and black. Gambier is the pale variety, while black catechu is obtained from the tree Acacia Catechu.

Uses: Medicine: All parts of the plant have astringent properties. The leaves of the plant contain a tannin called catechin which has a high pH value, making it acidic. Younger leaves of the plant have a higher catechin content than the older ones. In India, gambier was used as skin lotions since, supposedly, remote times. The Malays also use gambier as a lotion and apply it to treat burns. In paste form, it is used to treat scurf. It has commonly been used by the Indians and Malays to treat diarrhoea and dysentery, and as a gargle for sore throat. In Borneo, gambier has been used in the treatment of sciatica and lumbago.

Other uses: Gambier Catechu yields a colour known as "Cutch Brown" which is used for dyeing and tanning cotton, wool and silk. It is also used on leather, such as calf and kip skins. The common 'khaki' colour is obtained from it.