304 



Miss M. Wheldale and Mr. H. LI. Bassett. 



O O OH 



H0/V\-/ \0H HO./V\|^ \0H 



\A/ CH \/\/ CH 



HO CO HO CO 



Apigenin. Luteolin. 



As pointed out by Smiles,* the more intensely coloured flavones contain 

 two hydroxyl groups in the ortho position with respect to one another, 

 whereas the arrangement in apigenin is not so productive of colour. 



The close connection between the structure of the two substances, and the 

 fact of their occurrence together in Reseda luteola, also favour the assumption 

 that the yellow Antirrhinum pigment is luteolin. The presence of luteolin 

 in the allied genus Digitalis is also of interest. 



In order to corroborate this suggestion, attempts were made to form both 

 the acetyl and benzoyl derivatives of the yellow pigment. The attempts 

 failed, owing partly to the small amount of pigment available, and partly to 

 the following difficulties. In the case of the acetyl derivative, the method of 

 dissolving the pigment in caustic soda or pyridine and adding acetyl chloride 

 apparently failed to acetylate the pigment completely. The method 

 employed by Perkin and others of boiling the pigment with acetic anhydride 

 and anhydroiis sodium acetate was not found satisfactory when dealing with 

 such small amounts of substance, since there were produced simultaneously 

 brown decomposition products, from which it was impossible to isolate the 

 derivative. In attempts to benzoylate the yellow pigment by the Schotten- 

 Baumann method, the same difficulties arose, together with a further one, 

 namely, the fact that the melting point, 201° C, of the benzoyl derivative of 

 luteolin is only about 10° lower than that, 210-212° C, of the benzoyl 

 derivative of apigenin ; hence the possibility that the small amount of 

 product formed might be impure apigenin derivative produced from apigenin 

 retained in the luteolin used. It has been shown by Perkinf that in the 

 Schotten-Baumann method, under certain conditions, a tribenzoyl, instead of 

 a tetrabenzoyl, derivative may be formed. 



Finally, attempts were made to form the benzol sulphonyl derivative 

 described by Fleischer^ as obtained from digitoflavone, the latter substance 

 being extracted from Digitalis leaves and subsequently shown to be identical 

 with luteolin. Fleischer's benzol sulphonyl derivative was obtained by 



* Smiles, S., ' The Relations between Chemical Constitution and some Physical 

 Properties,' London, 1910. 



t Perkin, A. G., " Notes on Luteolin and Apigenin," ' Chem. Soc. Journ., Trans.,' 1902, 

 vol. 81, p. 1174. 



•J Fleischer, F., loc. cit. 



