i64 CAROTENOID HYDROCARBONS OF KNOWN CONSTITUTION X 

 Optical activity: y-Carotene is optically inactive. 



Partition test: On partition between petroleum ether *and 90% methanol, 

 y-carotene is entirely epiphasic. 



Chromatographic behaviour: y-Carotene is more strongly adsorbed from 

 petroleum ether solution than /5-carotene. In the chromatogram on calcium 

 hydroxide or alumina it is found above /9-carotene and below lycopene. 



Detection and estimation: The separation of y-carotene from other carotenoid 

 hydrocarbons is achieved by chromatographic adsorption on alumina or 

 calcium hydroxide. Its presence can be established by the determination of the 

 absorption maxima. 



Physiological properties: y-Carotene exhibits strong vitamin A potency^^^. 

 Several investigators have reported on the supposed function of y-carotene in 

 the sexual metabolism of various plants^^^. 



Stereoisomers of y-carotene: By the treatment of y-carotene with heat, light, 

 or iodine, or fusion of the crystals, Zechmeister and PolgAr^^' partly con- 

 verted y-carotene into various cis-trans isomers. None of these compounds has 

 so far been obtained in the crystalline state. The different isomers are separated 

 by means of chromatographic adsorption on calcium hydroxide and can be 

 distinguished by their absorption spectra. 



A bsorption maxima 

 (in petroleum ether) 



Neo-y-carotene U 489 457 m/x 



(Natural y-Carotene) 494 461.5 m/< 



Neo-y-carotene A 486 455.5 m/x 



Neo-y-carotene B 486 455.5 m/^ 



Neo-y-carotene H 489 457.5 m/i 



Neo-y-carotene A' 485.5 455 m/i 



Neo-y-carotene B' 486 455 m/t 



Neo-y-carotene G' 483 452 mix 



(y-Carotene with all-c?s configuration) 456 m// 



The vitamin A activities of y-carotene and pro-y-carotene have recently 

 been investigated by Zechmeister and co-workers^^'^. 



6. PRO-y-CAROTENE C4oH5g 



In 1941, Zechmeister and Schroeder^^^ found a new polyene pigment in 

 the fruit of Butia capitata which they termed pro-y-carotene. The new pigment 

 has also been observed in the following plants: Pyracantha angustifolia 

 Schneid^^", Evonymus fortunei L.^^^ and Mimulus longiflorus Grant^^^. 

 References p. 165-iyo. 



