African Marigold - Tagetes patula(CHAPTER VII. Flavonol Group.)(Osa artikkelista)

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.

Quercetagetin was isolated from the flowers of the African marigold, Tagetes patula, by Latour and Magnier de la Source (Bull. Soc. Chim., 1877, (ii.), 28, 337), who state that it also occurs in other varieties of the same plant. In appearance and general properties it is described as resembling quercetin, the colouring matter of quercitron bark, and from this fact, together with its origin, the name quercetagetin is evidently derived. On the other hand, according to these authors, its crystalline form, solubility in 60 per cent, alcohol, and the numbers obtained on analysis indicated that it was distinct from quercetin C₂₇H₂₀O₁₂, and it was considered to possess the formula C₂₇H₂₂O₁₃ (anhydrous) or C₂₇H₂₂O₁₃, 4H₂O (air-dried). A preliminary re-examination of this colouring matter was made by Perkin in 1902 (Chem. Soc. Proc., 18, 75), and it has more recently been studied in greater detail by the same author (Chem. Soc. Trans., 1913, 103, 209). To isolate the colouring matter, which is largely present in the flowers as glucoside, a concentrated alcoholic extract is diluted with water which precipitates a viscous impurity, and this is removed by means of ether. The clear liquid treated when boiling with addition of a little hydrochloric acid deposits after cooling but a small bulk of the colouring matter, and repeated extraction of the solution with ether is necessary for its economical isolation. The crude product thus obtained can be crystallised from dilute alcohol, but for complete purification it is necessary to prepare the acetyl derivative, and after re-crystallisation to hydrolyse this in the usual manner.

[---]

Quercetagetin readily dyes mordanted fabrics shades of a generally similar character to those given by other well-known flavonol colouring matters.
Chromium. Dull olive-yellow.
Aluminium. Yellow-orange.
Tin. Brown.
Iron. Brownish-black.

A trace of a more sparingly soluble colouring matter is present in the flowers and represents about 1 per cent, of the crude quercetagetin referred to above. It crystallises from alcohol in somewhat indefinite groups of minute needles and dissolves in alkaline solutions with an orange colour passing to green on dilution with water. Though similar in appearance to rhamnetin (quercetin monomethyl ether) it does not contain a methoxy group.

Dyeing Properties of the Flowers.

Employing mordanted woollen cloth, the following shades are produced:
Chromium. Yellowish-Brown.
Aluminium. Pale dull yellow.
Tin. Deep yellow-orange.
Iron. Brownish-black.

These possess a somewhat redder character than those given by quercitron bark, and are similar to, though not so red as those from patent bark. As quercetagetin mainly occurs in the flowers as glucoside, their tinctorial effect is evidently due to this latter.