nRubian(Chem) One of several color-producing glycosides found in madder root.
Century Dictionary and Cyclopedia
nrubianA bitter principle and colorproducing matter (C28H34O15) of madder. It is a glucoside, amorphous, very soluble in water and alcohol, and has a yellow color and a slightly bitter taste. It is a very weak dye by itself, but is decomposed on boiling with an acid, and deposits insoluble yellow flocks, which, after being separated by filtration and well washed, serve as dye for the same colors as those given by madder. The tinctorial power of these flocks is due to alizarin.