Transformation of haemins into bile pigments

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Abstract
"Green hemin" is prepared according to Warburg and Negelein by action of O on pyridine-hemochromogen in presence of hydrazine. A corresponding compound is obtained from mesohemin. The "green hemins" are characterized as pyridine-hemochromogens of isobiliverdins. The name "verdohemochromogens" is proposed. Their formation is due to oxidative scission of the porphyrin nucleus of the hemochromogen, catalysed by haem Fe. The "green ester," obtained by Warburg and Negelein by action of methyl alcoholic HC1 on green hemin, is identified with the ferrichloride of biliverdin ester. From mesohemin the ferrichloride of mesobiliverdin is obtained in the same way. The ferri-chlorides can be transformed into the biliverdin esters and these can be identified with products prepared from bilirubin of gall stones. Since hemin has been synthesized, its transformation into biliverdin means the total synthesis of the latter. It is suggested that the formation of bile pigments in the animal body proceeds in a similar way, yielding biliverdin (dehydrobilirubin), which is afterwards reduced to bilirubin. The nature of the unsaturated side-chains of bilirubin and biliverdin is discussed and it is suggested that they are vinyl groups like those of hemin.

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