CHEMISTRY OF CHLOROPHYLL: THE CAROTINOIDS 49 



Chlorophyll, Hemoglobin, and Evolution. — From an evolu- 

 tionary point of view it has been highly suggestive to observe 

 that there is a striking chemical similarity between chlorophyll, 

 the characterizing green pigment of plants, and hemoglobin, the 

 characteristic red-colored material of the blood of animals. If 

 chlorophyll is treated with an acid and then an alkali, the porphy- 

 rin resulting is called phylloporphyrin; and if hemoglobin is treated 

 in a similar manner, the substance hematoporphyrin is obtained. 

 These two porphyrins have almost identical spectra and formulae. 

 The iron has been removed from the hemoglobin in the same way 

 that the magnesium was removed from the chlorophyll. 



A further connection between chlorophyll and hemoglobin is 

 shown by the fact that these two porphyrins give the same de- 

 composition products, as shown in the accompanying diagram: 



Chlorophyll Hemoglobin 



i i 



Phylloporphyrin Hematoporphyrin 



Hemopyrrol. 



Nentski and M archie wski (1901) obtained hemopyrrol from both 

 of them. The pyrrol ring is seen from the formula given on page 48 

 to be found in four different places in etiophyllin. Iron has been 

 found by Baly to be one of the best catalyzers for the formation 

 of the pyrrol ring, 



H H 



I I 

 C=C 



\nh 

 c=c 



H H 



and this may explain its importance in chlorophyll formation. 



If the formulae for chlorophyllin and hematin are compared, it 

 will be seen that the chief difference is the element at the center of 

 the molecule. In chlorophyllin it is magnesium while in hematin 

 it is iron. In agreement with this are the results of Kiister (1926), 

 who showed that both hemoglobin and chlorophyll can be derived 



