Asbarg(CHAPTER VII. Flavonol Group.)

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.

Asbarg consists of the dried flowers and flowering stems of the Delphinium zalil, which is found in great quantity in Afghanistan. The dyestuff is collected and taken to Multan and other Punjab towns, from which it is conveyed all over India. It is much used in silk dyeing for the production of a sulphur-yellow colour known as "gandkaki," and, together with Datisca cannabina, to obtain a similar shade on alum-mordanted silk; it is also used in calico-printing. The flowers, which are bitter, are likewise employed medicinally as a febrifuge.

The colouring matters of asbarg are present entirely as glucosides, and are best isolated in the crude condition by digesting the boiling aqueous extract with a little sulphuric acid (Perkin and Pilgrim, Chem. Soc. Trans., 1898, 268). A brownish-yellow powder thus separates, which contains three substances: isorhamnetin, quercetin, and kaempferol.

Isorhamnetin, C₁₆H₁₂O₇, the sparingly soluble constituent, forms yellow needles, resembling rhamnetin in appearance. With lead acetate in alcoholic solution, an orange-red precipitate is formed, whilst ferric chloride gives a greenish-black coloration. Fused with alkali, phloroglucinol and protocatechuic acid are produced, and when air is aspirated through its alkaline solution, phloroglucinol and vanillic acid are obtained.

With acetic anhydride isorhamnetin gives a tetra-acetyl derivative, C₁₆H₈O₇(C₂H₃O)₄, colourless needles, melting-point 195-196°; and with methyl iodide a trimethyl ether, which is identical with quercetin tetramethyl ether. As, moreover, by the action of hydriodic acid wrhamnetin yields quercetin, its constitution can only be represented as follows: [KUVA PUUTTUU]

The dyeing properties of isorhamnetin are similar in character to those given by kaempferol. isoRhamnetin is also present in yellow wallflowers (Cheiranthus cheiri) (Perkin and Hummel), and in red clover flowers, Trifolium pratense (Power and Salway, Chem. Soc. Trans., 1910, 97, 245). A description of the more soluble colouring matters quercetin (quercitron bark) and kaempferol (Delphinium consolida) is given elsewhere.

In dyeing properties asbarg closely resembles quercitron bark, but yields with aluminium mordant a purer or less orange-yellow. It is, however, a much weaker dyestuff, having but 35 per cent, the dyeing power of quercitron bark. The colouring matter of the flowers, apart from the flowering stalks, is present to the extent of 3,47 per cent.

The stems and flowers of the D. saniculafolium give shades analogous to, though somewhat weaker than, those yielded by the D. zalil.