227 



27. L. MAKCHLEWSKI n\. c. Barwiki, otrzymane przy dziataniu izatyny 

 na wyci^gi Isatis tinctoria. ( On colonrhig nxittei-s ohtnhmhle by 

 the action of isatin ou extrocts of Isatin finrtofln). (Matières co- 

 lorantes obtenues par l'action de l'isaiine sur les extraits d'Isatis tinctoria). 



Isatis tinctoria cuntains. as shown l)v Dr. E. Öchunck. a sub- 

 stance which under certain conditions splits up yielding indigotin 

 and suijar. Some years ago, when engaged in the study of the con- 

 stitution of glucosides in gênerai, I expressed the opinion that in- 

 dican is a glucosîde of indoxyl. an opinion which has been proved 

 to be correct by Hoogewerff and ter Meulen in their brilliant expéri- 

 mental research on Polygonum tinctorium'). The authors hâve isoiated 

 from this plant a crystalline body which is hydrolised under the 

 influence of acids yielding glucose and indoxyl. which latter in its 

 turn is oxidised under the influence of air giving indigotin. 

 About the same time Beijerinck -) had also paid attention to the che- 

 mistry of indigo producing plants, and arrived at the conclusion 

 that not all thèse plants eontain the glucoside of indoxyl, but that 

 on the contrary Isatis tinctoria does not eontain this glucoside at 

 ail, but free indoxyl. These results were very unexpected, especially 

 considering that Dr. Schunck, who for the first tinie put forward 

 the glucoside nature of indican, based his views upon results oh- 

 tained from the study of this plant. 



Beijerinck supports his contention bv the following observa- 

 tions. If extracts of Indigofera lepto.stachya or Pcjlygonuni tincto- 

 rium are treated with isatin at elevated température, a formation 

 of indirubin, the condensation product of indoxyl and isatin. will 

 take place only after treating the said extracts with acid.s, the rôle 

 of thèse acids being to split up the preexisting glucoside into indo- 

 xyl and glucose. Now, using an extract of Isatis tinctoria the forma- 

 tion of indirubin takes place withont previous treatment witli acids, 

 and it may be inferred from this lact, that Isatis tinctoria contains 

 free indoxyl and not a Compound of it. 



The action of isatin on extracts of woad bas been studied 



') KoninklijUo Akademie v.au Wuttenscliappen te Amsterdam. Froceedings 

 etc. 1900, p. 520. 



'l 1. c. 189H, p. 120. 



