APHANIN 



303 



sorbing zone, giving the appearance of a single wide absorption band with 2 

 maxima. The wide absorption range has no sharp hmits and although the two 

 maxima are clearly recognised their centres can only by approximately 

 determined." 



Solutions of the pigment in petrol and methanol are yellow, solutions in 

 benzene, chloroform and pyridine are orange, and solutions in carbon disulphide 

 are red-orange. 



Optical activity: Aphanin shows no optical rotation. 



Partition test: On partition between petroleum ether and 90% methanol, 

 the pigment is found entirely in the upper layer; if 95% methanol is used, 

 however, the lower layer is also weakly coloured. 



Chromatographic behaviour: Aphanin is adsorbed somewhat more strongly 

 than j3-carotene, but more weakly than aphanicin, on alumina from petrol 

 solution. If the chromatogram is developed with ether, the colour changes to 

 brown-red; on washing with benzene or chloroform, it becomes dark violet. 



Colour reactions: Concentrated aqueous hydrochloric acid gives no blue 

 colouration with an ethereal solution of aphanin. A chloroform solution of the 

 pigment assumes a deep blue colour which gradually changes to blue-green on 

 addition of concentrated sulphuric acid. With antimony trichloride in chloro- 

 form, aphanin exhibits a brownish-violet colour which turns blue-violet on 

 fading*. 



Physiological properties: Aphanin exhibits vitamin A activity which is about 

 half as great as that of j3-carotene^^. 



Detection and estimation: The separation of aphanin from the other carote- 

 noids of Aphanizomenon flos-aquae is carried out by means of chromatographic 

 adsorption on alumina. By this means, the pigment can be separated from the 

 more strongly adsorbed aphanicin and can be identified by its absorption 

 spectrum. 



Derivatives 

 Aphanin oxime C40H55ON: 



This compound is obtained on treating a solution of aphanin in pyridine 

 with free hydroxy famine. For purification, the crystallised oxime is chromato- 

 graphed on alumina and recrystallised from a mixture of benzene and methanol. 

 M.p. 208° (corr.). The oxime is rather sparingly soluble in benzene. 



For further colour reactions, cf. the original communication, Z. physiol. Chem. 

 251 (1938) 109. 



References p. J41-343. 



