456 X. BILE PIGMENT FORMATION, ETC. 



that sulfhemoglobin appears to be most closely related to hemoglobin, 

 since it is reconvertible to protohemochrome, while choleglobin 

 appears to be most closely related to the verdoheme compounds, 

 since its iron — like that of verdoheme compounds — is easily 

 detached. Research in this field is complicated by the fact that none 

 of these pigments have yet been obtained in a pure state, that most 

 of them are unstable, and that the prosthetic group is attached more 

 firmly to the protein than in hemoglobin. 



2. MODEL EXPERIMENTS ON BILE PIGMENT 

 FORMATION. VERDOHEMOCHROMES 



2.1. Introduction 



When hemochromes are exposed to atmospheric oxygen in the 

 presence of a great variety of reducing substances, such as polyhydric 

 phenols, adrenaline, ascorbic acid (1469), sulfhydryl compounds, 

 extracts of yeast or minced animal or plant tissues (850), green com- 

 pounds are obtained. The complete literature is given in the papers 

 of Fischer and Lindner (850) and of Lemberg (1681). Several workers 

 had speculated on a relationship of these substances to bile pigments, 

 but Fischer and Lindner found the green pigments to contain iron 

 and to possess an absorption spectrum different from that of any 

 known bile pigment. Warburg and Negelein (£952) obtained the 

 green compound by coupled oxidation of pyridine hemochrome with 

 hydrazine and, under the name "green hemin," related it to the 

 green hematin compounds of chlorophyll derivatives. 



By the action of methanolic hydrochloric acid on their green 

 hemin, these authors obtained a crystalline ester of the composition 

 C36H4o06N4FeCl4, which they considered to be a green hemin ester. 



On incubation of hemoglobin or hematin with liver brei or liver 

 extracts at 70° C. and pH 7-8, Schreus and Carrie (2^70) obtained a 

 green, ether-soluble pigment, which the authors considered, however, 

 to be a secondary oxidation product of bilirubin. 



In 1935 Lemberg (1681), realizing the fact that the bilatrienes 

 (biliverdins) were more closely related in structure to the porphyrins 

 than the biladienes-(a,c) (bilirubins) (Fig. 1), reinvestigated this 

 problem. He identified the "green hemin ester" of Warburg and 

 Negelein as the "double salt" of biliverdin dimethyl ester hydro- 

 chloride and ferric chloride — bilatriene dimethyl ester ferrichloride, 

 C35H3906N4 • FeCU — which he had previously obtained from bili- 



