300 CAROTENOIDS OF UNCERTAIN STRUCTURE XIV 



6. APHANIN C40H54O 

 History and Occurrence 



Although the pigments of blue algae have been repeatedly investigated 

 within recent years, our present knowledge concerning these compounds is 

 still very incomplete. In 1927, Kylin^^ investigated extracts of the blue algae 

 Calotrix scopulorum by capillary-analytical methods, and found, besides 

 carotene, three new pigments. These were not, however, isolated in a pure 

 state and analysed. 



In 1936, Heilbron and Lythgoe investigated the carotenoids from 

 Oscillatoria ruhescens^^, and reported the presence of j3-carotene and xantho- 

 phyll, as well as of two new pigments, myxoxanthin and myxoxanthophyll 

 (cf. p. 225). Very recently, Karrer and Rutschmann" reinvestigated the 

 polyene pigments from Oscillatoria rubescens and found a previously unknown 

 acidic pigment, oscillaxanthin, besides /3-carotene, zeaxanthin, myxoxanthin 

 and myxoxanthophyll, but no xanthophyll (cf. p. 335). 



TisCHER^^ investigated the carotenoids of the blue algae Aphanizomenon 

 flos-aquae and was able to isolate four new polyene pigments besides j8-carotene. 

 He proposed the term aphanin, aphanicin, flavacin and aphanizophyll for 

 these pigments. They have so far only been observed in Aphanizomenon flos- 

 aquae. 



Preparation^^ 



The algae Aphanizomenon flos-aquae are collected Irom their aqueous suspen- 

 sions by means of nets, freed from impurities and dehydrated with ethanol. The 

 residue, still alcohol-moist, is mixed with sand and ammonium sulphate and ex- 

 tracted at room temperature with ether which has been freshly distilled from 

 sodium. The ether is removed by distillation and the aqueous ethanolic residue is 

 extracted with petroleum ether (Extract A). The petroleum ether-insoluble 

 pigments from the alcoholic layer r re obtained in the form of a red flocculent 

 precipitate b}^ salting out with ammonium sulphate. The alcoholic extracts which 

 remain after the dehydration of the algae also yield a small amount of red pigment, 

 which is combined with that obtained by salting-out and dissolved in pyridine 

 (Extract B). 



The material remaining after extraction with ether is once more extracted with 

 ethanol at 40° (Extract C). 



The petroleum ether extract A is adsoibed on alumina and the chromatogram 

 is developed with petrol. The carotenoids are adsorbed on the column in the 

 following downward sequence: 1. aphanicin, 2. aphanin, 3. flavacin and 4. /3-caro- 

 tene*. 



a) Aphanicin: The pigment is again chromatographed on alumina, saponified 

 with methanolic potassium hydroxide after elution and once more chromatographed 

 on alumina. Aphanicin is eluted with petrol containing a little ethanol and the solu- 



For a detailed description, see J. Tischer, Z. physiol. Chem. 251 (1938) 109. 

 References p. 341-342. 



