150 



IV. BILE PIGMENTS 



constitution was elucidated by Siedel and Moller {2558) (cf. Fig. 27). It is 

 probably a mixture of side chain isomerides. 



Mesobilifuscin (with an ethyl instead of the vinyl group) is the prosthetic 

 group of myobilin {cf. above). The "body II" obtained by Fischer as a by- 

 product of the sodium amalgam reduction of bilirubin to mesobilane {861, 

 p. 693), was identified as the same substance and evidently arises from bili- 

 fuscin present as an impurity in the bilirubin. The structure of mesobili- 

 fuscin was proved by its formation from the corresponding a.a'-dibromo- 

 pyrromethene with sodium methoxide (replacing bromine by hydroxyl), 

 and also in the way illustrated in Figure 27. The methyl ester was not 

 obtained crystalline; its melting point is 172-176° C. The absorption spec- 

 trum shows no distinct absorption band, the absorption rising from 500 mju 

 toward a faint maximum at 280 m/x. The zinc salt is insoluble and does not 

 fluoresce. 



From the sweat and urine of certain sheep showing a golden coloration of 

 their wool, Rimington and Steward {2275) isolated a brown pigment which 

 they called lanaurin. It gave no typical bile pigment reactions. Analyses 

 indicated the formula C33H36O10N4 but can equally well be interpreted as 

 indicating C16H18O5N2. From this and from observations on the products 

 of reduction by hydroiodic acid it can be concluded that lanaurin is identical 

 with bilifuscin and thus a dipyrrolic pigment. The conclusion of Rimington 

 that the golden coloration is caused by a hereditary hyperactivity of hemo- 

 globin breakdown is in agreement with this {cf. Chapter X, 9.). 



Probably the "copronigriri' of Watson, an artifact obtained from human 

 feces {2971), belongs to the same class, and Siedel suggests the same for 

 "xanthoruhin" {609,687,1897) {cf. Chapter XI, 7.1.). The absorption spec- 

 trum of xanthorubin in etheral solution {609,687) is, however, in disagree- 

 ment with Siedel's assumption, and suggests rather that xanthorubin is a 

 bilipurpurin. 



8.2. Pentdyopent 



The reaction series given in Figure 27 also supplies evidence of the nature 

 of pentdyopent. Bingold has described in a series of papers {270,272-275, 

 277) the formation of a substance with an absorption band at 525 m;u (hence 

 the name pentdyopent). It is formed when hematin or hemoglobin is exposed 



HO 



N 

 H 



^C^N^OH 



/. 



H 



HO N C N OH 

 H ,/ H 



O 



A B 



Fig. 28. Suggested formulas for propentdyopent (A) and pentdyopent (B). 



to rather large concentrations of hydrogen peroxide in the absence of catalase 

 and the colorless solution (propentdyopent) then treated with potassium 

 hydroxide and dithionite. In ammonia the band is found at 540 myu. The 



