4 a-CAROTENE 159 



aqueous hydrochloric acid, the acid layer assumes a very weak, unstable blue 

 colouration. 



Solvent: Absorption maxima: 



Carbon disulphide 503 471 m^u 



Benzene 484 455 m/x 



Petroleum ether 471 442 mfj, 



Chloroform 483 454 m/z 



a-Carotene mono-epoxide occurs in the blossoms of various plants {Trago- 

 -pogon pratensis, Ranunculus acery^^. According to von Euler, a-carotene mono- 

 epoxide possesses vitamin A potency"^. 



CH3 CH3 



(] , CHo CHo 



A \V 



CHa C=CH CH3 CH3 CH3 CH3 C 



CH, C CH— C=CHCH=CH-C=CHCH = CHCH=C-CH=CHCH=C-CH=CH-CH CHj 



Flavochrome H3C-C CHj 



CH 



Flavochrome is formed by the action of dilute acids (e.g. hydrogen chloride 

 in chloroform) on a-carotene mono-epoxide. It crystalhses from a mixture of 

 benzene and methanol in thin lustruous yellow plates, m.p. 189° (uncorr., in 

 vacuum). It exhibits a colour reaction with hydrochloric acid, similar to that 

 of a-carotene mono-epoxide. 



Solvent: Absorption maxima: 



Carbon disulphide 482 451 m^ 



Benzene 462 434 m/i 



Petroleum ether 450 422 m/x 



Chloroform 461 433 m/z 



Flavochrome does not exhibit growth-promoting properties. Both a-caro- 

 tene mono-epoxide and flavochrome are epiphasic in the partition test. Flavo- 

 chrome occurs in Ranunculus acer and Tragopogon pratensis. 



^:6-Dihydro-a-carotene and ^:6'dihydro-^-carotene C^^r,^: 



PoLGAR and Zechmeister"' treated solutions of a-carotene or /5-carotene 

 in petroleum ether with cold concentrated hydrogen iodide, and in both cases 

 obtained several chromatographically separable reduction products, from 

 which two pigments could be isolated in the crystalline state. 



From the analytical data, the results of catalytic hydrogenation, the ab- 

 sorption maxima, and the absence of isopropylidene groupings, these compounds 

 References p. 165-170. 



