Bile pigment formation in vitro from haematin and other haem derivatives

first showed that the green haemin of Warburg & Negelein (1930), on treatment with methanolic hydrogen chloride, gave a ferric salt of a biliverdin ester from which the ester of biliverdin itself could be obtained by shaking the chloroform solution of the salt with water. Lemberg concluded that green haemin possessed the structure of a verdohaemochromogen, i.e. it possessed an open bile pigment structure maintained as a ring by the central iron atom to which pyridine was still co- ordinated. The pyridine-free material (verdohaematin) on reduction with sodium amalgam gave a urobilinoid pigment with an intense Ehrlich reaction, and showed urobilin-like behaviour with zinc acetate and iodine. Condensation with ammonia reclosed