Catechu

Catechu (also known as cutch, cashoo, or Japan earth) is an extract of any of several species of Acacia&mdash;but especially Acacia catechu&mdash;produced by boiling the wood in water and evaporating the resulting brew.

Catechu (called katha in Hindi) is an astringent and has been used since ancient times in Ayurvedic medicine as well as in breath-freshening spice mixtures. Black Catechu has recently also been utilized by Blavod Drinks Ltd. to dye their vodka black. 

Also called cutch, it is a brown dye used for tanning and dyeing and for preserving fishing nets and sails.

White cutch, also known as gambier, gambeer, or gambir, has the same uses.