7 CAPSORUBIN 251 



CH, CH, CH3 CH, 



\V \V 



C CH3 CH3 CH3 CH3 c 



CH2 C-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-CO CH3 



I II 



CH2 0*0x13 



CHa 



Solvent Absorption maxima 



Polyene Ketone (III) Capsanthin 



Carbon disulphide 543 503 543 503 m^ 



Petroleum ether 503 473 503 475 m/z 



Most of the colour reactions exhibited by capsanthin on treatment with 

 different acids and metalHc chlorides^* are also given by the polyene ketone. 

 The two compounds, however, differ somewhat in their behaviour towards 

 concentrated aqueous hydrochloric acid : the acid layer is coloured red on shaking 

 with an ethereal solution of capsanthin but remains colourless in the case of 

 the polyene ketone. 



7. CAPSORUBIN C4oHgo04 



History and Occurrence 



In 1934, Zechmeister and von Cholnoky^"^ isolated a new pigment, 

 capsorubin, during the chromatographic purification of capsanthin. Capsorubin 

 has so far only been found in Capsicum annuum. 



Preparation 



The paprika pods are pre-treated with ethanol, and then extracted with 

 petroleum ether. The combined extracts are concentrated in vacuum and the 

 pigment esters are chromatographed on calcium carbonate. After repeated chro- 

 matographic adsorption, the capsorubin ester is saponified with methanolic pot- 

 assium hydroxide, and the pigment is finally chromatographed repeatedly on 

 calcium carbonate from carbon disulphide solution. For further purification, the 

 pigment is crystallised from a mixture of benzene and petrol. The yield of analyti- 

 cally pure pigment amounts to about 130 mg from 5 kg of pods. 



Chemical Constitution^'^^' ^^^ 

 CHq CHo CHo CH.J 



CH3 CH3 CH, CH3 C 



/\ I I I 1 /\ 



OHj 00-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-CO CH2 



HOCH CH,-CH, HoC-CH, CHOH 



CH2 OH2 



References p. 253-255. 



