A colorless compound formed in the intestines by the reduction of bilirubin. Some is excreted in the feces where it is oxidized to urobilin. Some is reabsorbed and re-excreted in the bile as bilirubin. At times, it is re-excreted in the urine, where it may be later oxidized to urobilin.

Synonyms: Urobilinogen, 14684-37-8, 21H-Biline-8,12-dipropanoic acid, 2,17-diethyl-1,4,5,10,15,16,19,22,23,24-decahydro-3,7,13,18-tetramethyl-1,19-dioxo-