Bromsulfthalein (also known as bromsulphthalein, bromosulfophthalein, and BSP) is a phthalein dye used in liver function tests. Determining the rate of removal of the dye from the blood stream gives a measure of liver function.[1] The mechanism by which the liver detoxifies BSP is to attach it to glutathione which is the body’s master antioxidant.
References
^Rosenthal, Sanford M. (1925). "Clinical Application of the Bromsulphalein Test for Hepatic Function". JAMA: The Journal of the American Medical Association. 84 (15): 1112. doi:10.1001/jama.1925.02660410020008.