Rheum emodi, also known as Indian rhubarb is a plant of Mongolian origin. Roots of this plant are used as an astringent and purgative.
It gives a yellow color and also contains a number of derivatives and is used to dye wool and silk fibres. Coloring component of Rheum emodi has close resemblance with a typical anthraquinonoid type disperse dye.
Silk and woolen fabrics are dyed with the colorant extracted from Rheum emodi to make various shades of colors ranging from yellow to olive green.
The main colouring component of the root of Rheum emodi is chrysophanic acid, when extracted found to be associated with a number of compounds.