igo CAROTENOIDS CONTAINING HYDROXYL GROUPS XI 



b) Mutatoxanthin: 



\/ 



C CH3 CH, 



CHjj C=CH CH3 CH3 CH3 CH3 C 



HOCH C CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-C CH, 



CH2I HsC-C CHOH 



CH3 Mutatoxanthin " \ / 



CH2 



Mutatoxanthin was first obtained by Karrer and Rutschmann^^ by the 

 action of dilute hydrochloric acid on natural violaxanthin (cf. p. 195). It has 

 the formula C4oH5g03, and contains 10 double bonds and 2 hydroxyl groups®^. 

 The nature of the third oxygen atom was first established by the partial 

 synthesis^^ of the pigment, in which mutatoxanthin was obtained by the action 

 of acidic chloroform on zeaxanthin mono-epoxide (antheraxanthin) (cf. p. 62). 

 The formula given above for mutatoxanthin is in accord with all the properties 

 of the pigment. This formulation also explains the formation of mutatoxanthin 

 from violaxanthin. By the action of dilute hydrochloric acid on the latter, one 

 of the epoxide groups is converted into a more stable furanoid system, while the 

 oxygen of the other epoxide group is split off. (With regard to the formula of 

 violaxanthin, see below). 



Mutatoxanthin crystallises from methanol or from a mixture of benzene 

 and methanol. M.p. 177° (uncorr., evacuated capillary). On partition between 

 methanol and petroleum ether, the pigment is found in the lower layer. On 

 treating an ethereal solution of mutatoxanthin with concentrated aqueous 

 hydrochloric acid, a blue colouration is produced which is weaker than that 

 given by auroxanthin (cf. p. 197) and not very stable. 



Solvent: Absorption maxima: 



Carbon disulphide 488 459 m/i 



Ethanol 457 427 m/^ 



Benzene 468 439 m// 



Petroleum ether 456 426 m/i 



Chloroform 468 437 m^u 



Pyridine 473 443 m/z 



c) Violaxanthin, Zeaxanthin di-epoxide: 



CH, CH, CH, CH, 



C CH3 CH3 CH3 CH3 C 



/\ II I I /\ 



CHj C-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-C CH^ 



)0 0{ 



HOCH C C CHOH 



\ y \ Violaxanthin / \ / 



CHa CH3 H3C CHa 



References p. 214— 2iy. 



