200 CAROTINOIDS AND RELATED PIGMENTS 



Isolation oj Carotin 



Carrots. The carrot root naturally suggests itself as the most 

 available source of the pigment carotin. Several methods have been 

 proposed by various investigators, each of which may be indicated 

 briefly. 



The method of Arnaud (1886) was to submit the fresh grated car- 

 rots to heavy pressure and add an excess of neutral lead acetate to 

 the juice. The precipitate was filtered off, dried in vacuum and added 

 to the pressed carrot pulp, which had also been dried. The combined 

 material was then washed with carbon disulfide at a low temperature. 

 Crude carotin crystallized out of this extract on concentrating it to a 

 low volume and allowing it to stand, if sufficient material had been 

 used. Arnaud obtained three grams from 100 kgs. of carrots by this 

 method. He states that most of the impurities could be washed away 

 from the crude crystalline material by cold petroleum ether. 2 Final 

 purification was secured in Arnaud's work by dissolving the crystals 

 in the least possible amount of carbon disulfide and then adding a 

 large excess of absolute alcohol, in which carotin is practically in- 

 soluble. This was followed by a spontaneous crystallization from 

 cold pertoleum ether, a final washing with cold absolute alcohol, and 

 drying in vacuum. 



Kohl's (1902e) method for isolating carotin from carrots offers 

 certain advantages over that of Arnaud, particularly because smaller 

 quantities of extraction solvent are required. The carrots are sliced 

 and then boiled and pressed. The writer has noticed that there is 

 practically no loss of pigment in either the water in which the carrots 

 are boiled or in the press juice, inasmuch as the heat coagulation of 

 the proteins seems to fix the carotin in the tissues. Kohl washed the 

 first press cake with cold alcohol, pressed it again, ground it and 

 allowed it to dry in the air. A bright orange-red powder resulted 

 if well colored carrots were chosen. Kohl extracted this powder with 

 ether in an extractor of the continuous type until all the pigment was 

 extracted. The ether was removed by evaporation, and saponification 

 carried out in the extraction flask by boiling for an hour with alcoholic 

 potash. The evaporation of the alcohol was carried out in the same 

 flask in a current of CO 2 , and the dried soap extracted with chloro- 



2 It is almost necessary to use a fat solvent in this case because of tbe high content 

 of oil in the carrot root. It is to be expected, also, that some pigment will be lost in 

 carrying out the operation. 



