132 



IV. BILE PIGMENTS 



lie 10 m/x more toward the infrared than those of the corresponding meso 

 compounds. 



Mesobihpurpurin I can be distinguished from mesobiHviohn as well as 

 from mesobihpurpurin II by the behavior of its chloroform solution toward 



HO A^C A.^cA/^C^fA OH 

 H H H H 



biliverdin 



A ArA A„A A„/x A 



HO N 



purpurin I 

 dihydr oxy biladiene - (a,b) 



N 



OH 



O, 



HO 



/\ ApA ArA ,Ar A^/ 

 H H Ho H O 



CO 



chrysin 

 dehydrobilene-(a)-one-(c) 



HO 



A^AcA 



H 



>^pA A 



N J^ N 



^ /CO 



o ^^ 



H 



purpurin II 

 dehydrobiladiene-(a,b)-one-fc) 



Fig. 20. Bilipurpurins and bilichrysins. 



aqueous hydrochloric acid. Shaking with 1% hydrochloric acid transforms 

 mesobihviolin into its hydrochloride, which remains in the chloroform phase 

 with blue color; it extracts mesobihpurpurin I from the chloroform as red- 

 violet hydrochloride and leaves mesobilipurpurin II in the chloroform as 

 neutral compound. Shaking the chloroform solutions with hydrochloric acid 

 of different concentrations appears to be a suitable test for differentiation of 

 bilipurpurins {1712). A curious phenomenon is the favoring of the hydro- 

 chloride formations in the chloroform phase by an increase of temperature. 

 Probably higher temperature favors the formation of an unstable, more 

 strongly basic tautomeric form in equilibrium with a less basic form. 



