Myrica nagi(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.

Myrica nagi (Thunb.). This is an evergreen tree belonging to the Myricaceæ met with in the sub-tropical Himalaya from the Ravi eastwards, also in the Khasia mountains, the Malay Islands, China, and Japan. It is the box-myrtle or yangma of China, and is synonymous with M. sapida (Wall.), M. rubra (Sieb. and Zucc.) and M. integrifolia (Roxb.). The bark is occasionally used as a tanning agent, and is said to have been exported from the North-West Provinces to other parts of India to the extent of about 50 tons per annum. In Bombay it is met with under the name of kaiphal, and in Japan as shibuki.

Myricetin, C₁₅H₁₀O₈, H₂O, the colouring matter, can be isolated from an aqueous extract of the plant by a similar method to that which is serviceable for the preparation of fisetin (see Young Fustic), but is more readily obtained in quantity from the Japanese commercial "shibuki" extract (Perkin and Hummel, Chem. Soc. Trans., 1896, 69, 1287; and Perkin, ibid., 1902, 81, 204).

The extract is treated with ten times its weight of hot water to remove tannin, and when cold the clear liquid is decanted off, the residue washed twice in a similar manner, and well drained. The product is extracted with boiling alcohol, and the solution evaporated until crystals commence to separate. On cooling these are collected (the filtrate A being reserved) and washed first with strong and then with dilute alcohol. A complete purification is best effected by converting the colouring matter into its acetyl derivative, and when pure hydrolysing this in the usual manner. Myricetin crystallises in yellow needles, melting at about 357°, and closely resembles quercetin in appearance. Dilute potassium hydroxide solution dissolves myricetin with a green coloration, which, on standing in air, becomes first blue, then violet, and eventually brown coloured. Alcoholic lead acetate gives an orange-red precipitate, and ferric chloride a brown-black coloration.

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Myricetin dyes mordanted woollen cloth the following shades, which are practically identical with those given by quercetin:
Chromium. Red-brown.
Aluminium. Brown-orange.
Tin. Bright red-orange.
Iron. Olive-black.

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Myricitrin, C₂₁H₂₂O₁₃, H₂O, or rather C₂₁H₂₀O₁₂, 2H₂O, the glucoside, is present in the alcoholic filtrate A, from the crude myricetin, from which it separates on standing. The crystals are collected, washed first with alcohol, then with dilute alcohol, crystallised from water, from alcohol, and finally from water. Myricitrin forms pale yellow, almost colourless leaflets, melting at 199-200°, and is soluble in alkalis with a pale yellow tint. Aqueous lead acetate gives an orange-yellow precipitate, and alcoholic ferric chloride a deep greenishblack coloration. In appearance it cannot be distinguished from quercitrin, and the shades given by the two substances on mordanted woollen cloth are practically identical.
Chromium. Full brown-yellow.
Aluminium. Full golden-yellow.
Tin. Lemon-yellow.
Iron. Brown-olive.

When hydrolysed with dilute sulphuric acid myricitrin yields rhamnose and myricetin, according to the equation C₂₁H₂₀O₁₂+H₂O=C₁₅H₁₀O₆+C₆H₁₂O₅, and is analogous to quercitrin which in a similar manner gives rhamnose and quercetin. In addition to myricetin the M. nagi contains a trace of a glucoside of second colouring matter, which is probably quercetin.

The dyeing properties of myrica bark are generally similar to those of other yellow mordant dyestuffs. On wool with chromium mordant it gives a deep olive-yellow, and with aluminium a dull yellow, similar to the colours obtained from quercitron bark, but much fuller; with tin mordant it gives a bright red-orange, redder in hue than that given by quercitron bark; with iron mordant it gives a dark greenish-olive like that obtained from quercitron bark, but again fuller.

On cotton with aluminium and iron mordants it dyes colours which are more similar to those obtained from old fustic than from quercitron bark. Some specimens of myrica bark are exceedingly rich in colouring matter, and a sample examined by Hummel and Perkin (J. Soc. Chem. Ind., 1895, 14, 458) possessed much stronger dyeing power than old fustic.

According to Satow (J. Ind. Eng. Chem., 1915, 7, 113) (Abst. Chem. Soc., 1911, 149), the colouring matter of the M. rubra has the formula C₁₅H₁₀O₈, and is identical in some of its properties with myricetin. By fusion with sodium polysulphide and sulphur a product is obtained which dyes cotton a deep sepia colour, though if copper sulphate, manganese sulphate, or ferrous sulphate is added to the fused mass, substances possessing a bluish or bluish-grey colour are produced. By fusing myricetin with sulphur alone a brown-yellow compound is obtained. A yellow dye may also be obtained by nitrating myricetin sulphonic acid.