The identification of monoconjugates of bilirubin in bile as amide derivatives.

Recent reports have shown that bilirubin can be esterified in vivo to form a variety of acyl glycosides (Kuenzle, 1970; Heirwegh, Van Hees, Leroy, Van Roy & Jansen, 1970). The question as to whether these conjugates are present in bile as monoconjugates as well as diconjugates remains in doubt. Indirect evidence for the existence of bilirubin monoglucuronide, based on the estimation of the molar ratio of bilirubin to glucuronic acid and on the production of equal amounts of azobilirubin and of azobilirubin glucuronide on diazotization of an isolated bilirubin conjugate, has been presented by several groups of workers (Billing, Cole & Lathe, 1957; Giovanetti, Maggiore & Vivaldi, 1961; Jacob-