Chemical structure of a new family of bile pigments from human urine.

Seven bilirubin metabolites negative to the diazo reaction were identified in the urine of healthy persons by enzyme-linked immunosorbent assay (ELISA) using the anti-bilirubin monoclonal antibody 24G7. Two of the seven metabolites were isolated and their chemical structures were determined using fast-atom bombardment-mass spectroscopy (FAB-MS) and 1H-NMR. The two metabolites are 1,14,15,17-tetrahydro-2,7,13-trimethyl-1,14- dioxo-3-vinyl-16H-tripyrrin-8,12-dipropionic acid and 1,14,15,17-tetrahydro-3,7,13-trimethyl-1,14-dioxo-2-vinyl-16H- tripyrrin-8,12-dipropionic acid. They are regioisomers of each other. The two bilirubin metabolites are novel tripyrrole biocompounds and belong to a third group of bile pigments following biliverdin and bilirubin. We gave these compounds the generic names biotripyrrin-a and biotripyrrin-b, respectively.