COPPER BILIRUBINATE AND BLACK PIGMENT GALLSTONE

A series of copper bilirubinate complexes (CuBR) was synthesized in solution and in solid state to mimic the black color of the black-pigment gallstone and to explore the formation mechanism of the gallstone in vitro. The variation of the copper contents of these samples indicated that CuBR also exhibits nonstoichiometric characteristics from the FTIR study, i.e., both the so-called acid and neutral copper complex moieties exist in CuBR. The NH groups in pyrrole and lactam groups of bilirubin (H(2)BR) are binding to the copper ions. An EPR study demonstrates the generation of free radicals and the variation of its electronic structure and conjugation system in the skeleton of H(2)BR molecule during complex formation. A polymer of CuBR may form through the reaction of H(2)BR with copper ions. (C) 1995 John Wiley & Sons, Inc.