Polygonum cuspidatum(CHAPTER I. The Anthraquinone 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.

P. cuspidatum (Sieb. et Zucc.) is common in India, China, and Japan, and is referred to by A. Henry in a paper entitled "Chinese Names of Plants" (Journal Royal China Branch of Royal Asiatic Society, 22, New Series, No. 5, 1887) as "Kan-yen, wu-tzu," the name employed at Patung for its root, which is said to be used for dyeing yellow.

According to Perkin (Chem. Soc. Trans., 1895, 67, 1084) the main constituent of this root is a glucoside, polygonin, C₂₁H₂₀O₁₀, forming orange-yellow needles, melting-point 202-203°, which, when hydrolysed by acids, gives emodin and a sugar:
C₂₁H₂₀O₁₆ + H₂O = C₁₅H₁₀O₅ + C₆H₁₂O₆

A trace of a second glucoside is also present, from which the emodin monomethylether, melting-point 200°, previously found to exist in the root-bark of the Ventilago madraspatana (Gaertn.) (Chem. Soc. Trans., 1894, 65, 932), was obtained.