234 PIGMENTS 



RELATIONSHIP BETWEEN CHLOROPHYLL AND 

 HEMOGLOBIN. 



With a view to the further elucidation of the constitution 

 of the chlorophyll molecule, especially in regard to the com- 

 plex to which the carboxyl groups are attached, the oxidation 

 of the porphyrins by means of chromic acid in the presence 

 of sulphuric acid has been studied by Marchlewski * and by 

 Willstatter and Asahina.f These investigations point to the 



C-C 

 existence of the grouping I )N in the molecule, since 



CC/ 



the two chief oxidation products are found to be pyrrole 

 derivatives of the formulae 



CH 3 . C CO\ CH, . C CO\ 



II >NH ' || \NH 



COOH . CH 2 . CH ? . C CO/ CH 3 . CH 2 . C CO/ 



Haematinic acid imide Methylethylmaleinimide 



The former substance, which is the imide of a tricarboxylic 

 acid known as haematinic acid, of the formula 



CH 3 . C COOH 



II 

 COOH . CH 2 . CH 2 . C COOH 



has also been obtained from haemoglobin, the red colouring 

 matter of the blood, and a connexion between haemoglobin 

 and chlorophyll is thereby established. 



The relationship between this haematinic acid imide and 

 haemoglobin is as follows : 



Haemoglobin is readily hydrolysed by dilute acids or 

 alkalis with the formation of haematin ; this latter substance 

 contains iron, which can, however, be readily removed by 

 treatment with hydrogen bromide in acetic acid solution, J 

 giving an iron free compound haematoporphyrin, both 

 haematin II and haematoporphyrin on oxidation yield the 

 haematinic acid imide mentioned above. 



* Marchlewski : " Chem. Zentralbl.," 1902, I, 1017. 

 f Willstatter and Asahina : " Annalen," 1910, 373, 227. 

 JNencki and Zaleski : " Zeit. physiol. Chem.," 1900, 30, 423. 

 It should be noted that chlorophyll derivatives free from magnesium are by 

 analogy called porphyrins : cf. Fhylloporphyrin, etc. 



||Kiister: "Zeit. physiol. Chem.," 1899, 28, i ; 1900, 29, 185. 



