Ellagic Acid(CHAPTER XII. Diphenyl-Dimethylolid 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.

Ellagic acid, C₁₄H₆O₈, is obtained from numerous tannin matters which contain an ellagitannin by boiling the aqueous extract with dilute sulphuric acid. In many cases it is found in the free state, due probably to the hydrolysis, by fermentation, of the ellagitannin or ellagic acid glucoside originally present, and such a fermentation frequently occurs when aqueous extracts of the tannin matters are allowed to stand for some time.

Divi-divi (Caesalpinia coriaria, Willd.), (Löwe, Zeitsch. anal. Chem., 1876, 14, 40), myrobalans (Terminalia chebula, Ratz.), (Löwe, ibid.), algarobilla (Caesalpinia brevifolia), (Zolffel, Beilstein, 2, 1085), and valonia (Quercus aegilops, Linn.) yield considerable quantities, of ellagic acid, and are the best natural sources of this material. It has also been isolated from oak galls (Chevreul, Ann. Chim. Phys., 1828, (2), 9, 329); oak bark (Etti, Monatsh., 1880, 1, 226); the bark of Picea excelsa (Link.), (Strohmer, ibid., 1881, 2, 539); pomegranate rind (Rembold, Annalen, 1867, 143, 288); Quebracho colorado (Perkin and Gunnel, Chem. Soc. Trans., 1896, 69, 1307); Arctostaphylos uva-ursi (Spreng.) and Coriaria myrtifolia (Linn.), (Perkin, ibid., 1900, 77, 424); Hæmatoxylon campeachianum (Linn.), (Perkin, ibid., 1897, 71, 1137); the fruit of Caesalpinia digyna (Rottl.), (Nierenstein, Chem. Zeit., 1909, 87); and the bark of Terminalia catappa (Linn.), (ibid.). In fact, ellagic acid probably always occurs, if only in minute quantity, in all plant products which contain gallotannin. Most interesting are the Oriental bezoar stones, concretions which are found in the stomachs of goats and other animals, and consist largely of ellagic acid. These originate, without doubt, from the fact that the animal has fed upon plants in which some quantity of an ellagitannin is present.

Ellagic acid was first discovered by Chevreul (Ann. Chim. Phys., loc. cit.) in oak galls, and more closely examined by Braconnot (ibid., 9, 187). According to Pelouze, it possessed the composition C₇H₄O₄ (ibid., 54, 356); whereas Merklein and Wöhler (Ann. Chem. Pharm., 55, 129), who isolated it from bezoar stones and termed it "bezoaric acid," showed that its true formula is C₁₄H₆O₈.

The precipitate of crude ellagic acid, which is produced by boiling the tannin extract with dilute mineral acid, is purified by washing with alcohol and subsequent recrystallisation. A similar procedure is also satisfactory with the deposits so frequently produced by fermentation and alluded to above. Ellagic acid is most readily crystallised from pyridine (Perkin and Nierenstein, Chem. Soc. Trans., 87, 1416), and the product, which contains pyridine of crystallisation, is washed with alcohol.

Löwe (Zeitsch. Chem., 1868, 4, 653) was the first to prepare ellagic acid synthetically by oxidising gallic acid with arsenic acid, and this was subsequently accomplished by Ernst and Zwenger (Annalen, 1871, 159, 32) by heating ethyl gallate with sodium carbonate solution in the presence of air, and by Griessmayer (ibid., 1871, 160, 55) by heating gallic acid with water and iodine. It is readily produced by oxidising gallic acid dissolved in acetic acid by means of potassium persulphate and sulphuric acid (Perkin and Nierenstein, loc. cit.), and together with flavellagic acid by the addition of potassium persulphate to a solution of gallic acid in sulphuric acid (Perkin, ibid., 1906, 89, 251). Under similar conditions, gallotannin produces ellagic acid (Nierenstein, Ber., 1908, 41, 3015; and 1909, 42, 353), and it can also be prepared by boiling the tannin with hydrogen peroxide solution (ibid., 1907, 40, 917). Herzig and Bronneck obtained good results by passing air through an ammoniacal solution of gallic acid, and also of gallotannin (Montash., 1908, 29); whereas Sisley (Bull. Soc. chim., 1909, [4], 5, 727) prepared ellagic acid from tannin by means of alcoholic potassium hydroxide solution. According' to Rûpe, a 60 per cent, yield is produced when gallic acid in sulphuric acid solution is oxidised with sodium nitrite (Chemie d. naturl. Farbstoffe, 1909, 2, 162).

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The tinctorial properties of ellagic acid are somewhat feeble, but in 1887 it was placed on the market by Messrs. Meister, Lucius, & Brüning, under the name of "Alizarin Yellow in paste" and was recommended as yielding, with chromium mordants, greenish-yellow shades of considerable permanence.

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