RELATED COMPOUNDS 661 



7. Methods for the Preparation of Carotenoids 



In the preparation of different carotenoids, the same general methods 

 apply. If the source of the material is a substance which contains a mix- 

 ture of different polyenes, the carotenoids are first extracted from the 

 saponified mixture with petroleum ether or with a similar solvent. The 

 carotenols can easily be separated from the hydrocarbons by extraction 

 with methanol (95-90%). In the preparation of a hydrocarbon, the 

 petroleum ether solution is washed several times to remove any dissolved 

 alcohol; it is then dried over a suitable dehydrating agent such as sodium 

 sulfate, after which the solution is chromatographed. The adsorption 

 zone of the desired fraction is removed as described earlier, the carotenoid is 

 eluted, the eluting agent is removed by washing with water, the solution is 

 dried, and the petroleum ether solution is again chromatographed. This 

 procedure may be repeated several times to obtain a product of satisfactory 

 purity. After it is eluted, it is transferred to a suitable solvent, which is 

 evaporated to a small volume. If the crj^stals are desired, it can be 

 allowed to crystallize in the cold. 



A similar procedure may be employed when the product belongs to the 

 group of carotenols. However, the carotenoid must be transferred to a 

 non-polar solvent such as petroleum ether or benzene before chromatog- 

 raphy. This is readily accomplished by the addition of sufficient water to 

 decrease the methanol to a 50% aqueous solution. It is then extracted 

 with petroleum ether, and the petroleum ether is finally washed with water 

 to remove any dissolved methanol. After drj^ing, as described above, the 

 solution is chromatographed. The product eluted from the adsorption 

 zone may be purified from hydrocarbons by a new extraction of the petro- 

 leum ether solution on 95% methanol. This may be rechromatographed 

 after being transferred to petroleum ether. Ultimate crystallization can 

 be carried out as described for the carotenes. For specialized methods of 

 preparation of the different carotenoids, the reader is referred to Zech- 

 meister's monograph. ^^ 



8. Related Compounds 



(1) Phytofluene 



One of the polyenes closely related to the carotenoids which is widely 

 distributed in nature is a colorless compound first isolated bj" Zechmeister 

 and Polgar."' It was later proposed that this compound be designated as 

 "phytofluene. "534 



a. Occurrence. Phytofluene has a distribution in plants which roughly 



5" L. Zechmeister and A. Polgdr, Science, 100, 317-318 (1944). 



"^ L. Zechmeister and A. Sandoval, Arch. Biochem., 8, 425-430 (1945). 



