II GAZANIAXANTHIN 313 



The behaviour of fucoxanthin towards hydrochloric acid has akeady been 

 described on p, 312. Willstatter and Page^^ showed that a definite amount 

 (4 mols) of hydrochloric acid is consumed in this reaction. The compound 

 formed has the formula 640115403.4 HCl. 



Crystalline fucoxanthin is fairly stable in air, no uptake of oxygen being 

 observed during a period of several weeks. However, the pigment absorbs water 

 from the air and forms various hydrates. If an ethereal solution of the pigment 

 is allowed to stand in the presence of iodine, a tetraiodide of fucoxanthin soon 

 crystallises. This derivative forms short, pointed, violet-black prisms with a 

 coppery lustre. M.p. 134-135° (corr., after slight sintering). 



Little is known concerning the pigments** designated as "fucoxanthin 

 a, b, c" and their homogeneity is uncertain; the same applies to "neofuco- 

 xanthin A" and "neofucoxanthin B"*^. 



II. GAZANIAXANTHIN 



History and Occurrence 



1938 ScHON isolates a new phytoxanthin, gazaniaxanthin, from the blossoms 

 of Gazania rigens^^. 



1943 Zechmeister and Schroeder*' propose a tentative formula for gazania- 

 xanthin. 



Preparation^'' 



1 kg of blossom leaves of Gazania rigens are dried at 40-50° and extracted with 

 petroleum ether at room temperature. After saponification with methanolic pot- 

 assium hydroxide, the pigment mixture is chromatographed on calcium hydroxide 

 from petroleum ether solution. Depending on the age of the blossoms, the yield of 

 gazaniaxanthin varies between 380 and 620 mg. 



Chemical Constitution 

 CH, CH, CH3 CH, 



C CH3 CH, CH, CH, CH 



/\ I I I I \ 



CH2 C-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-CH CH^ 



HOCH C-CHs HjC-C CH, 



\ y^ Gazaniaxanthin ( ?) \ / 



CH2 CHa 



According to Schon*^, gazaniaxanthin has the molecular formula C4oHg40 

 or C4oH5gO. The oxygen atom is present in the form of a hydroxyl group, as 

 shown by Zerewitinoff determinations and the preparation of an acetate. 

 On catalytic hydrogenation gazaniaxanthin absorbs 11 mols of hydrogen*'. 

 According to Zechmeister and Schroeder*' the molecular formula is C40H58O 

 References p. 341-243. 



