304 CAROTENOIDS OF UNCERTAIN STRUCTURE XIV 



The spectrum of aphanin oxime exhibits two bands. The Hmits of the wide 

 absorption band are less clear than in the case of aphanin and cannot be deter- 

 mined exactly^®. For various colour reactions of the oxime, the original commu- 

 nication^^ should be consulted. 



Aphanol C^^Yi^^O: 



During the reduction of aphanin with aluminium isopropoxide and iso- 

 propylalcohol a compound which shows the absorption spectrum of crypto- 

 xanthin is obtained amongst other products. According to Tischer^^ this 

 compound is identical in structure with cryptoxanthin. 



7. APHANICIN 



This pigment was first isolated by Tischer^^ from Aphanizomenon flos- 

 aquae*. 



Chemical Constitution 



Very little is yet known concerning the constitution of aphanicin. Various 

 considerations lead Tischer to regard aphanicin as a "di-carotenoid" of the 

 empirical formula CgoH^QgOg, consisting of 2 molecules of aphanin combined by 

 an oxygen bridge. As compounds of this type have not otherwise been 

 encountered in nature, nor prepared synthetically, this suggestion can only be 

 accepted with reserve. Experimentally the following results were obtained. The 

 elementary analysis of aphanicin gave the values C, 86.14%; H, 9.35% 

 (Calculated for C4(,H540: C, 87.20: H, 9.89%). The pigment formed an oxime, 

 found: N, 3.97%. (C40H55ON requires N, 2.48%. Calculated for C40H55ON. 

 yaNHgOH, 3.61 %**). The aphanicin molecule thus contains at least i carbonyl 

 group. On microhydrogenation, aphanicin absorbs 12 mols of hydrogen. As the 

 absorption spectrum of aphanicin is very similar to that of aphanin, it may 

 be assumed that the two compounds contain very similar or identical chromo- 

 phoric systems. Aphanicin has only about half the vitamin A activity of 



For the isolation of the pigment, see under aphanin, p. 300. 

 ** Addition products of free hydroxylamine and carotenoids have been observed, 

 J. Tischer, Z. physiol. Chem. 26y (1941) 281. 



References p. 341-343. 



