Asterin.(CHAPTER VIII. Pyran Group. Cyanidin and its derivates.)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Asterin is one of the pigments of the purple-red aster (Callistephus chinensis, Nees, syn. Aster chinensis, Linn.), and has been isolated by Willstatter and Burdick (Annalen, 1916, 412, 149), (cf. callistephin).

The colouring matter after separation from the pelargonidin derivative (callistephin) that accompanies it in the flowers as described on p. 268, was finally purified by recrystallisation from aqueous methyl alcoholic hydrochloric acid - containing but a very small per cent, of HCl - by allowing the alcohol to evaporate slowly.

Asterin chloride, C₂₁H₂₁O₁₁Cl, forms fine bronze-brown to redbrown crystals (prisms) having metallic lustre, which contain water of crystallisation and have the composition C₂₁H₁₂O₁₁Cl, 1½H₂O. Both the anhydrous and hydrated forms are isomeric with the respective forms of chrysanthemin chloride, but the crystals of the two pigments differ greatly.

The salt is soluble in water yielding a brown-red solution which assumes a more bluish tinge on dilution, then becomes colourless as the result of pseudo-base being formed. It gives reactions identical with those of chrysanthemin chloride in respect of ferric chloride, sodium carbonate, sodium hydrate, and distribution between amyl alcohol and aqueous acid, viz. with ferric chloride in alcoholic solution, a blue coloration; sodium carbonate added to an acid solution gives a violet colour, whilst sodium hydrate produces a blue; the distribution number for this compound resembles that for other monosaccharide anthocyans. On the other hand, it differs greatly from chrysanthemin chloride in respect of its solubility in acids, as may be seen from the following data given by Willstatter and Burdick:

	EtOH (Containing HCl)	0.5 per cent HCl	3 per cent HCl	7 per cent HCl	7 per cent. H2SO4
Asterin chloride	Easily soluble cold.	Very easily soluble.	Easily soluble.	Appreciably soluble cold; on slight warming very easily soluble.	Fairly easily soluble.
Chrysanthemin chloride	Fairly difficultly soluble.	Much less soluble.	Difficultly soluble.	Very insoluble, only appreciably soluble boiling, and rapidly separates on slight cooling.	Very easily soluble, much more so than asterin chloride.

On hydrolysis asterin chloride yields cyanidin chloride (1 mol.) and glucose (1 mol.).