CHAPTER I 



Mode of occurrence of carotenoids in plants 



and animals 



Detection and estimation of carotenoid pigments 



I. MODE OF OCCURRENCE IN PLANTS 



Relatively little information is available regarding the mode of occurrence 

 of carotenoids in plants. In view of their non-polar nature, the majority of 

 natural polyene pigments are insoluble in water and do not normally occur 

 dissolved in the celLfluid. An, exception is provided by crocetin which occurs 

 in the cell fluid in the form of its water-soluble gentiobiose ester, crocin. Water 

 solubility can be conferred not only by esterification with sugars, as in the 

 case of crocin, but also by combination with proteins. Esterification can occur 

 with the carotenoid carboxylic acids (e.g. crocetin, bixin and azafrin), while 

 combination with proteins has so far been observed mainly with polyene 

 pigments (e.g. astacene) occurring in animals. (Compare Menke^). 



The majority of vegetable carotenoids occur in the chromatophores. They 

 seldom occur crystalline, but are usually present in colloidal suspension in the 

 cell hpoids or in admixture with solid or semi-solid fats. Menke^ has recently 

 found that certain carotenoids in the plastids are combined with proteins; 

 this is in accord with the observations of Junge^ regarding the mode of occur- 

 rence of carotenoids in animals. According to Goldowski and Podolskaja^ 

 the carotenoids of the sunflower seeds occur in the aqueous and not in the oily 

 phase. This is in contrast to the findings of Savellis^, according to whom the 

 carotenoids are present in separate lipoid droplets in the chloroplasts. It will be 

 clear from these partly contradictory results that this question has not yet 

 been fully clarified. For further data and examples, reference should be made 

 to the original literature^. 



2. MODE OF OCCURRENCE IN ANIMALS 



Many attempts have been made in recent years to determine the fate of 

 carotenoids taken up with the vegetable food by the animal organism. It has 

 References p. 8-g. 



