RUBIXANTHIN 



173 



Source References 



Cuscuta salina G. Mackinney, /. biol. Chem. 112 (1935) 421. 



Cuscnta subinclusa, do. 



Gazania rigens K. Schon, Biochem. J. 32 (1938) 1566. — L. Zech- 



MEiSTER and W. A. Schroeder, /. Am. Chem. Soc. 



65 (1943) 1535. 

 Rosa canina, Rosa rubigi- 

 nosa, Rosa damascena R. Kuhn and H. Grundmann, Ber. 6y (1934) 341, 



1133. 

 Rosa rugosa H. Willstaedt, Svensk Kemisk Tidskr. 4J (1935) 113. 



Rubus Chamaemorus H. Willstaedt, Scand. Arch. Physiol. 75 (1936) 155. 



Preparation 



27 Kg of fresh, ripe hips (Rosa riibiginosa) are mashed, dehydrated with pure 

 methanol and dried at 37*^. The kernels are separated from the skins by grinding 

 in a mill and the skins are extracted at room temperature with a mixture of benzene, 

 absolute methanol and petroleum ether. The dark red extract is concentrated 

 (finalh' in vacuum) to a small volume and saponified with ethanolic potassium 

 hydroxide for two hours at 40°, and for a further two hours at room temperature. 

 After this period, the pigments are extracted with a benzene-petrol (1 :4) mixture, 

 the solution is washed free from alkali, dried and adsorbed on alumina. The chro- 

 matogram is developed with the same solvent mixture and the rubixanthin is 

 eluted with petroleum ether containing a little ethanol. The pigment is crystallised 

 from a benzene-petroleum ether (1 :5) mixture. The yield is about 400 mg. 



For further purification the crude pigment is again saponified by allowing a 

 benzene solution to stand with about 50 ml of 10% ethanolic potassium hydroxide 

 for 4 hours at 40°. The pigment is extracted with petroleum ether and the solvent 

 is removed by distillation. The rubixanthin is recr^^stallised from a mixture of 

 benzene and methanol. The yield of pure pigment amounted to 36 mg. 



Chemical Constitution 

 CHj CH3 CH, CH, 



C CHo CHo Clio CHo C, 



/\ \ I I I V 



CH2 C-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-CH CH 



I II II I 



HO-CH C-CH3 HgC-C CHg 



\y Rubixanthin \^ 



CHg CHj 



The formula for rubixanthin was proposed by Kuhn and Grundmann^. 

 Like y-carotene, the pigment takes up 12 mols of hydrogen on catalytic hydro- 

 genation and therefore contains i isocyclic ring. On ozonisation the pigment 

 yields 0.94 mol of acetone, evidently derived from the open end of the molecule. 

 Rubixanthin exhibits absorption bands of the same wavelength location as 

 y-carotene and the two polyenes may therefore be assumed to have the same 

 References p. 214-217. 



