124 IV. BILE PIGMENTS 



blue-violet, with a strong absorption band in the orange to yellow 

 parts of the spectrum; their zinc complex salts are green to blue with 

 a remarkably strong red fluorescence, a strong absorption band in 

 the orange, and a weaker one in the yellow. Such compounds have 

 been obtained: 



(a) by ferric chloride oxidation of mesobilane and mesobilene {S5S,1673, 



167 8-lGSO ,1690, 2550) ; 

 {b) from mesobilane with copper salts as copper complexes {777;800;861, 



p. 691; 1673); 



(c) as prosthetic groups of phycocyanin of algae (1673,1690); 



(d) from feces and urine {S61, p. 654; 1995 ;297 1-2973); 



(e) by synthesis (2550); 



(/) from the blue to violet stages of the Gmelin reaction or by oxidation of 



hiliruhins and biliverdins by nitrous acid (1680,1688,2552,2535,2556); 

 (g) by bromine oxidation of bilirubins (850,1269,2550); 

 (h) by treatment of bilirubins or biliverdins with iodine in the presence of 



zinc acetate (97,174,1680,1679,1711); 

 (?) from bilirubins and biliverdins with cupric salts (859,1605,1607 ,1673, 



1681); 

 (j) from biliverdins with quinone in alcohols (870) ; 

 (Ic) from oxidized verdohemochrome or choleglobin (1681,1712); 

 (I) from biliverdin by the action of oxygen liberated from oxyhemoglobin 



by acids (1680); 

 (m) by action of light on porpliyrin sodium complex salts (804)' 



We know now, particularly through the work of Siedel (2550,2552, 

 2553,2555,2556), that two main classes of biliviolinoid pigments 

 exist. The substances obtained by methods enumerated under a-d 

 are biladienes-(a,b), in fact always mesobiladiene-(2'a,5'b) (Fig. 14), 



ME MP PMME 



hq/ n c n c N C n ^oh 



H H H H. H 



Fig. 14. Mesobila(iiene-(2'a,5'b); mesobiliviolin. 



while those under e-m,, mainly formed by oxidation of rubins or 

 verdins, are products containing more oxygen, such as biladiene- 

 (a,b)-ones-(c), biladiene-(a,b)-diols or related substances (cf. Section 

 2.4. and Table III). 



Nomenclature. Siedel calls the former biliviolins, the latter bilipurpurins 

 and has separated mesobiliviolins from mesobilipurpurins by chromatogra- 

 phy. (The name "bilipurpurin" has been used before for the substance now 



