334 CAROTENOIDS OF UNCERTAIN STRUCTURE XIV 



occurs on shaking actinioerythrin with alkaHs was previously observed by 

 Fabre and Lederer'^* who were unable, however, to isolate a homogeneous 

 derivative and therefore assumed that decomposition of the pigment had taken 

 place. Violerythrin can only be obtained in relatively good yields by carrying 

 out the hydrolysis under very carefully controlled conditions. 



According to Heilbron and co-workers, a solution of actinioerythrin in 

 petroleum ether is shaken at room temperature with 2.5% methanolic sodium 

 hydroxide until the pigment has been entirely transferred to the lower layer (about 

 1 hour). The reaction mixture is then diluted with water, acidified with acetic acid 

 and extracted with ether. The ethereal solution is washed and dried, the solvent is 

 evaporated and the residue is crystallised from aqueous pyridine. 1 mg of viol- 

 erythrin was obtained in this way from 5 mg of actinioerythrin. 



The structure of this pigment is still unknown. It is not certain whether it 

 belongs to the carotenoid series. 



Violerythrin crystallises from aqueous pyridine in dark-violet micro- 

 crystals, m.p. 191-192°. It dissolves in carbon disulphide with a purple-red 

 colour, in alcohol and ether with a violet-red colour, in acetone and pyridine 

 with a blue colour, and in benzene with a deep-blue colour. The absorption 

 maxima in carbon disulphide are located at 625, 576 and 540 vafi. 



27. 8-CAROTENE 



WiNTERSTEiN®^ examined the shells of Gonocaryum pyriforme for carote- 

 noids and found besides lycopene, a-carotene, ^-carotene and y-carotene, a 

 new pigment for which he proposed the term 8-carotene. In the chromatogram, 

 S-carotene is found between y-carotene and j8-carotene. It could not be obtained 

 in a crystalline state so that its existence cannot be regarded as proven. 



Solvent: Absorption maxima: 



Carbon disulphide 526 490 457 mfi 



Chloroform 503 470 440 m/i 



Hexane 490 458 428 m/< 



WiNTERSTEiN^^ regards 6-carotene as the hitherto unknown carotene- 

 isomer derived from one half-molecule of a-carotene and one half-molecule of 

 y-carotene. 



28. FENICOTTERIN 



During an investigation of the pigments responsible for the red colour of 

 the fat of flamingo, C. Manunta^* discovered a carotenoid which is similar 

 to astacene but differs from the latter by a shorter-wavelength absorption 

 maximum (487 m/^ in carbon disulphide). As this compound was not obtained 

 in a pure state or analysed, its existence cannot be regarded as certain. 

 References p. 341-343. 



