Coupled oxidation of ascorbic acid and haemoglobin: Studies on the formation of bile pigments from choleglobin and verdohaemochromogen and on their isolation from erythrocytes.
IN a preliminary paper [Lemberg, Legge & Lockwood, 1938] we have already reported the isQlation of biliverdin (dehydrobilirubin) and of biliviolin from. choleglobin solutions. Under remarkably mild conditions haemoglobin is thus transformed. into bile pigments; these conditions are such as are found in the cells of organs forming bile pigment, except that acid was used for the removal of the iron. It will be shown in the present paper that the breakdown of choleglobin to bile pigments with the removal of iron probably occurs in the later stages of the reaction with ascorbic acid at a physiological pH. We describe here in greater detail the bile pigments obtained by acid splitting from choleglobin and verdohaemochromogen. The hope of gaining information on the constitutional differences between cholehaem and verdohaem by the study of the splitting products was not fulfilled owing to secondary reactiqns by which the primary splitting products are altered and owing to the complicated nature of the mixtures of bile pigments thus formed. Great difficulties had, therefore, to be overcome in working out quantitative methods enabling us to estimate the yield of bile pigment from the bile pigmenthaematin compounds. This was, however, achieved and we can now correlate the yield of bile pigments obtained from choleglobin solutions by splitting with' acids with the choleglobin concentration of these solutions. In the above-mentioned preliminary publicationwe had also reported the isolation of bile pigments from erythrocytes. In the present paper we describe these experiments in greater detail.