Bilirubin is a dark orange, yellow pigment that is the product of the breakdown of iron in the blood; it is conjugated in the liver and excreted in the bile.It is a member of the class of biladienes that is a linear tetrapyrrole with the dipyrrole units being of both exovinyl and endovinyl type
Bilirubin, an end product of heme catabolism, forms from the breakdown of erythrocyte hemoglobin in the reticuloendothelial system.Bilirubin is commonly found bound to serum albumin, when circulating in blood, in its dianion form. Bilirubin is also associated with bile salts, in its monoanion form.