470 X. BILE PIGMENT FORMATION, ETC. 



The oxidation product is dehydroascorbic acid; in the later stages 

 of the coupled oxidation, however, irreversible oxidation of ascorbic 

 acid beyond the dehydro stage takes place. Reduced glutathionje 

 protects ascorbic acid from oxidation and is oxidized instead, verdo- 

 hemochrome being formed with small concentrations of ascorbic acid 

 in the presence of an excess of glutathione. Pure glutathione alone 

 was not found by Lemberg and co-workers {1697) to form verdo- 

 hemochrome. The formation of a green compound in the reaction 

 with glutathione has been observed by Lyman and Barron {1794-), 

 but this was not verdohemochrome. 



Other hemochromes, such as a nicotine hemochrome, are also 

 oxidized to verdohemochromes. Denatured globin hemochrome is 

 oxidized very slowly and hematin not at all, their oxidation-reduction 

 potentials being so low that the ferric compound is not reduced by 

 ascorbic acid to a large extent. The optimal pll for the oxidation 

 of pyridine hemochrome to verdohemochrome is 7.6. In air at 37°C. 

 about twenty molecules of ascorbic acid are oxidized for one mole of 

 hemochrome oxidized to verdohemochrome. At a lower oxygen 

 pressure the ratio is smaller, since the rate of oxidation of ascorbic 

 acid is roughly proportional to the oxygen pressure, while verdohemo- 

 chrome formation, at least to a pressure as low as 30 mm. of mercury, 

 is almost independent of it. 



Other hydrogen donors which form verdohemochrome are hydra- 

 zine, pyrogallol, and adrenaline (850). The verdohemochrome formed 

 by oxidation of pyridine hemochrome with hydrogen peroxide in the 

 presence of pyrogallol was again mistaken for a chlorophyll derivative 

 by Haurowitz {1169). Veer {2863) has found that adrenochrome 

 converts hemochrome into verdohemochrome. This author assumes 

 th,at adrenochrome oxidizes hemochrome first directly and later by 

 means of hydrogen peroxide formed by autoxidation of leucoadreno- 

 chrome. A direct oxidation of hemochrome to verdohemochrome by 

 a quinone appears unlikely. It is more probable that the solution of 

 pyridine hemochrome prepared by pyridine treatment of erythrocytes 

 contained reducing substances; adrenochrome is reduced by reduced 

 pyridine nucleotides to leucoadrenochrome {104-4)- 



Cysteine in the presence of copper was also found to yield verdo- 

 hemochrome, while copper-free cysteine, and glutathione (with and 

 without copper) led to the formation of a little of a hemochrome with 

 an absorption band at 585 m/x, perhaps a hemochrome with carbonyl 

 side chains {1698). 



