4 ZEAXANTHIN 187 



Physalien has been partially synthesized from zeaxanthin and palmitic 

 acid chloride, thus confirming its constitution. 



PhysaHen is best prepared from physalis cups^^, the pigment content of 

 which is exceptionally large, amounting to 0.9-1.8% of dry weight. A third 

 of the pigment consists of cryptoxanthin (cf. p. 176). 



Physalis cups are dried at 40-50°, coarsely ground and exhaustively extracted 

 with benzene at room temperature. The combined extracts are concentrated in 

 vacuum to a small volume and the polyene wax is precipitated with acetone. The 

 precipitation is not carried out all at once, but at intervals of several hours, each 

 precipitate being filtered separately. The mother liquors are finally diluted with 

 much ethanol and set aside in the cold. In this way additional amounts of pigment 

 are obtained. The purification of physalien is carried out as follows: the pigment 

 wax is dissolved in hot benzene and fractionally precipitated in the hot with 

 methanol. The first fractions sometimes contain a waxy colourless substance, which 

 must be separated from the solution by filtration through a steam-jacketed filter. 

 The subsequent fractions yield the physalien. It is purified by re-crystalUsation 

 from a mixture of benzene and methanol. 



The purification of crude physalien can also be achieved more simply by dis- 

 solution in about 60 parts of hot benzene, followed by addition of 160 parts of hot 

 ethanol. On cooling, the pigment wax separates and can be purified by crystalli- 

 sation from a mixture of benzene and methanol. 1 g of the crude products yield 

 about 0.5 to 0.7 g of pure physalien. 



Physalien can also be isolated from Physalis berries^*. 2 kg of berries yield 

 about 1 g of polyene wax. L. Zechmeister and von Cholnoky^^ also describe the 

 isolation of the pigment from fresh Lycium berries, 5 kg of which yielded 5 g physalien. 



Proferties 



Physalien crystallises from a mixture of benzene and methanol in long, 

 flat rods, or in fine needles. It can also be obtained in the form of stout needles. 

 From cyclohexane and ethanol, the pigment separates in flat, dark red prisms, 

 several millimeters long. In larger quantities, physalien has the appearance 

 of a fiery brilliant red powder, with the consistency of a hard wax. It melts at 

 98.5-99.5°. It is very easily soluble in carbon disulphide, benzene, chloroform, 

 and carbon tetrachloride, and readily soluble in petroleum ether, hexane, 

 tetralin, decalin, ether and pyridine. Cyclohexane, glacial acetic acid and acetic 

 anhydride readily dissolve the pigment in the hot, but only sparingly in the 

 cold. The compound is almost insoluble in ethanol and acetone. 



According to Kuhn and Brockmann^^, physalien is optically inactive. The 

 positions of the absorption bands are indistinguishable from those of zeaxanthin. 

 Quantitative extinction measurements are reported by Hausser and Smakula^'. 

 On standing in air, physalien slowly absorbs oxygen, which results in a lightening 

 of the colour, lowering of the m.p. and increase in the solubility in ethanol. 

 Physalien dissolves in concentrated sulphuric acid to give a dark blue solution^. 

 Further colour reactions are de scribed by KuH N and Wiegand^^. 

 References p. 214—21'j. 



