Which Compound in certain plant -Juices can liberate 

 iodine from potassium iodid? 



By 



K. Aso, 



Assistant Professor in the University of Tokyo 



Some time ago Kastle and Loewenhart 1 ) endeavored to 

 render probable the hypothesis that the oxidizing actions of 

 plant Juices are caused by organic peroxids, and Bach and 

 Chodat 2 ) observed the liberation of iodine by tousching a fresh 

 section of the stein of Lathraea with a paper moistened with 

 iodid of potassium starch, wich also was attributed to an organic 

 peroxid. However the further Observation that plant Juices soon 

 lose this property is not in favor of the view, that this oxidi- 

 zing principle would be identic with the oxidase characterized 

 by the guaiacum blue reaction, since this can still be observed, 

 although weaker, with a plant juice after standing a few days. 

 Also the further interesting Observation of these authors that 

 in the wilting of a plant the iodine reaction disappears first, 

 speaks against the identity of this oxidizing principle with the 

 common oxidase (laccase) 8 ). I have made a series of tests with 

 the juices of potato tubers, young pea plants, shoots of Nelumbo, 

 Colocasia, Bambusa and Hordeum, and also the roots of radish 

 plants wich objects yield the guaiacum reactions for oxidase 

 and peroxidase very well, but not the iodine reaction. As I 

 supposed that these juices might contain some substance which 

 interfered with the formation of iodine starch by binding the 

 iodine immediately after being liberated, I have treated those 

 juices with an excess of absolute alcohol and after washing the 

 precipitates, containing the oxidizing enzyms, with alcohol they 

 were dissolved again in some water. These Solutions also yiel- 

 ded the guaiacum reactions upon oxidase and peroxidase very 



!) Americ. ehem. Jonrn. XXVI. 1901. No. 6. Dez. 

 -i Ber. Deut. ehem. Gesell. XXXV. S. 2466. 



3 ) Also Eaudnitz arrived at the conclusion that the iodine reaction 

 is not due to any of the known oxidases. 



