Natural Flavone(CHAPTER V. The Flavone 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.

Very interesting is the occurrence of flavone in nature (Müller, Chem. Soc. Trans., 1915, 107, 872). It is well known that many varieties of the primula possess on their flower stalks, leaves, and seed capsules a characteristic dust termed by gardeners "meal" or "farina," and this is most pronounced on varieties recently obtained from China and Japan. This powder, examined by Hugo Müller who obtained it mainly from the [Primula] P. pulverulenta and P. japonica, dissolves readily in benzene and boiling ligroin, and the concentrated solution on cooling became semi-solid owing to the separation of crystalline tufts.

It possessed the formula C₁₅H₁₀O₂, melted at 99-100°, and on boiling with dilute sodium hydroxide gave slowly a yellow solution, with formation of a small quantity of acetophenone, and the latter could be obtained in greater quantity by the action of methyl alcoholic sodium hydroxide. Employing methyl alcoholic barium hydroxide, a reagent not previously suggested for the degradation of flavone compounds, Müller obtained a substance C₁₅H₁₂O₃. This by the action of alkalis was converted into salicylic acid and acetophenone and evidently consisted of hydroxy-benzoyl-acetophenone (0-hydroxy-dibenzoyl-methane)
OH.C₆H₄.CO.CH₂.CO.C₆H₅

The compound C₁₅H₁₀O₂ was thus without doubt flavone, and it is interesting to note that though hydroxybenzoyl-acetophenone was assumed by Feuerstein and v. Kostanecki (Ber., 1898, 31, 1758) to be the first product of the hydrolysis of this substance, its isolation in this manner had not previously been effected.

The function which flavone exercises in the economy of the plant life of the primula is difficult to explain, though it may be of service on account of its repellent action towards water.