Rhamnus frangula(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
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1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

The bark of the alder buckthorn, R. frangula (Linn.), a shrub widely distributed throughout Europe, is employed in medicine chiefly in the form of a fluid extract as a mild purgative. Since the beginning of the last century the bark of this plant has been submitted to repeated examination, but an account of the earliest researches need not be recorded here. Casselmann (Annalen, 1857, 104, 77) was the first to analyse its main crystalline constituent which he termed frangulin, and this he extracted from the bark by means of ammonia. Faust (Annalen, 1872, 165, 229) by the hydrolysis of frangulin with hydrochloric acid obtained, in addition to a sugar, a substance he termed frangulic acid, and as by the distillation of this compound with zinc-dust anthracene was produced he concluded it to be a dihydroxy-anthraquinone isomeric with alizarin.

Liebermann and Waldstein did not prepare frangulin (Ber., 1876, 1775) but studied the colouring matter obtained from the bark by means of caustic soda solution, evidently the same substance as Faust's frangulic acid. This they isolated by sublimation and found to consist of emodin, and suggested that the hydrolysis of frangulin with acids might probably be represented by the following equation:
C₂₁H₂₀O₁₀ + H₂O = C₁₅H₁₀O₃ + C₆H₁₂O₆

Faust (Pharm. Zeitschrift fur Russland, 17, 257), on the other hand, considered that Liebermann and Waldstein's compound was not in reality emodin but rather a trihydroxydimethyl or a trihydroxyethyl- anthraquinone.

The subject was next studied by Schwabe (Arch. Pharm., 1888, 26, 259), who devoted special attention to frangulin. To this he assigned the formula C₂₁H₂₀O₉, and obtained from it by hydrolysis emodin and a sugar. This latter, which he did not isolate in a pure condition, he regarded as the rhamnodulcite of Liebermann. Finally Thorpe and Robinson (Chem. Soc. Trans., 1890, 57, 38) and Thorpe and Miller (ibid., 1892, 61, 1) submitted frangulin to detailed examination, and showed that, as Schwabe had stated, its correct formula is C₂₁H₂₀O₉. When hydrolysed it yields emodin, and rhamnose, which was isolated in a crystalline condition, and as a result the reaction may be thus expressed:
C₂₁H₂₀O₉ + H₂O = C₁₅H₁₀O₅ + C₆H₁₂O₅

For the preparation of frangulin the crushed bark is first treated with ligroin to remove wax and chlorophyll and subsequently extracted with alcohol. The extract is evaporated to dryness with sand, the powdered product extracted with ether, and after distilling off the ether the residue is treated with a little alcohol. On standing the solution deposits a mixture of emodin and frangulin together with a small quantity of a more sparingly soluble substance, and these can be separated by fractional crystallisation from alcohol.

Frangulin is an orange-yellow crystalline powder sparingly soluble in alcohol and melts at about 225°. It is readily susceptible to hydrolysis, and this indeed occurs to a slight extent by mere boiling with alcohol.

The sparingly soluble substance which contaminates the crude frangulin, the presence of which was also observed by Schwabe, crystallises from alcohol in golden-yellow needles, melting at 202 203. It dissolves in sulphuric acid with a red coloration, in dilute alkalis with the same tint, and is almost insoluble in ammonia. It appears to possess the formula C₁₅H₁₀O₅, being thus isomeric with emodin, though Perkin (Chem. Soc. Trans., 1895, 67, 1084) has suggested its possible identity with the emodin methyl ether C₁₆H₁₂C₅ of the Ventilago madraspatana and Polygonum cuspidatum, with which in melting-point and property it closely agrees.

Senna Leaves(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.
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Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Senna consists of the leaves of various species of cassia which are employed in medicine on account of their purgative properties. It has been the subject of numerous investigations and was long reputed to contain chrysophanic acid.

According to Tschirch and Hiepe (Arch. Pharm., 1900, 238, 427), these leaves contain gluco-sennin, a yellow crystalline substance, probably a glucoside of emodin, senna-emodin, C₁₅H₁₀O₅, melting-point 223-224°, senna-iso-emodin, C₁₅H₁₀O₅, and senna-chrysophanic acid, C₁₅H₁₀O₄, which melts at 223-224°. Senna-rhamnetin, yellow needles, which does not melt below 260°, and a substance C₁₄H₁₀O₅ are also present. Tutin (Chem. Soc. Trans., 1913, 103, 2006), who examined Tinnevelly, Lima and Peru senna leaves, C. angustifolia (Vahl), and the Alexandrian senna leaves, C. acutifolia (Delile), could not confirm the statements of Tschirch and Hiepe as to the presence of senna-iso-emodin or senna- chrysophanic acid.

The anthraquinone derivatives isolated consisted solely of aloe-emodin, C₁₅H₁₀O₅, and rhein, C₁₅H₈O₆, and these were present partly in the free condition and partly as glucosides. Senna leaves also contain kaempferol, C₁₅H₁₀O₆ (see Delphinium consolida), and a new glucoside of this substance, kaempferin,C₂₇H₃₀O₁₆6H₂O, melting-point 185-195°. In addition to the above-mentioned compounds, the senna leaves from Lima and Peru contained isorhamnetin, C₁₆H₁₂O₇, identical with that first isolated by Perkin from the yellow wallflower (Chem. Soc. Trans., 1896, 69, 1658), and this is probably the so-called sennarhamnetin of Tschirch and Hiepe.

Rumex ecklonianus, Rumex nepalensis(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.

RUMEX ECKLONIANUS.

Rumex ecklonianus (Meisner) is a herb indigenous to South Africa which possesses medicinal properties of a mild -purgative nature. Tutin and Clewer (Chem. Soc. Trans., 1910, 97, 6) examined the over-ground portion of the plant, and found it to contain chrysophanic acid, emodin, emodin mono-methyl ether and kaempferol.

RUMEX NEPALENSIS.

According to Hesse, the root of Rumex nepalensis (Wall), does not contain chrysophanic acid, but there is present in addition to two other substances, one he termed rumicin, which is isomeric with it.

Rumicin, C₁₅H₁₀O₄, golden-yellow leaflets, melts at 186-188°, and is soluble in caustic potash solution with a purple-red coloration. With hydriodic acid it yields chrysophanohydranthrone.

Nepalin, C₁₇H₁₄O₄, orange needles, melts at 136°, is insoluble in alkali carbonates, but dissolves in caustic potash, forming a purple solution. Diacetyl-nepalin, C₁₇H₁₂O₄(C₂H₃O)₂, crystallises in brownish- red rhombohedra, melting-point 181°.

Nepodin, the main constituent of the root C₁₈H₁₆O₄, greenish-yellow prisms, melting-point 158°, is distinguished from the preceding compounds by its solubility in solutions of the alkali carbonates. The diacetyl compound forms pale yellow rhombohedra which darken at 180°, and melt with decomposition at 198°.

Rhubarb, Rhein, Rheinolic acid, Alizarin(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.

RHEIN.

Rhein was isolated from rhubarb by Hesse (Annalen, 1899, 309, 43), whereas Oesterle and Babel (Schweiz. Woch. Chem. Pharm., 1904, 42, 329) showed that Tilden's aloe-xanthin prepared by the oxidation of barbaloin, and to which he had assigned the formula C₁₅H₁₀O₆, was a mixture of aloe-emodin and rhein. More recently its presence in rhubarb root has been confirmed by Tutin and Clewer (loc. cit.). It crystallises from pyridine in glistening orange-yellow needles melting at 318° (Tutin and Clewer), 314° (Oesterle), and is soluble in dilute alkaline solutions with a red colour. According to Oesterle it possesses well-defined tinctorial property and gives on fabrics mordanted with aluminium and chromium yellow shades.

The relationship between aloe-emodin and rhein and the constitution of these compounds has been elucidated by Robinson and Simonsea (Chem. Soc. Trans., 1909, 95, 1085). Whereas rhein yields only a diacetyl compound, and this is soluble in sodium acetate solution, further proof of the presence of a carboxyl group is afforded by the fact that this substance on hydrolysis and esterifi cation readily yields an ester, which by saponification is again converted into rhein. As aloe-emodin C₁₅H₁₀O₅ containing three hydroxyl groups is converted by oxidation with chromic acid into rhein C₁₅H₆O₄(OH)₂ in which but two are present, it is clear that one of the hydroxyls of aloe-emodin must be contained in a CH₂OH group and the oxidation process be represented as follows:
C₁₄H₅O₂(OH)₂CH₂OH + O₂ = C₁₄HC>₂(OH)₂COOH + H₂O

Aloe-emodin is thus the carbinol and rhein the corresponding carboxylic acid of a dihydroxy-anthraquinone.

To obtain an insight into the nature of this latter, Robinson and Simonsen prepared its dimethoxy derivative by converting dimethyl rhein amide, C₁₄H₅O₂(OMe)₂CONH₂, into amino-dimethoxy-anthraquinone, C₁₄H₅O₂(OMe)₂NH₂, and then eliminating the amino group in the usual way. The properties of this dimethoxy compound, according to these authors, indicate it to consist of iso-chrysazin dimethyl ether.

The constitutions of rhein, aloe-emodin, and chrysophanic acid may therefore be expressed thus: [KUVA PUUTTUU]

The following derivatives of rhein have been obtained:
Diacetyl-rhein, C₁₅H₆(C₂H₃O)₂O₆, needles, melting-point 247-248° (Oesterle), 258° (Tutin and Clewer), Tetranitro-rhein (Leger), C₁₅H₄O₆(NO₂)₄, short efflorescent prisms, Rhein ethyl ester, C₁₄H₅O₂(OH)₂COOEt, needles, melting-point 159°, Diacetyl-rhein ethyl ester, plates, melting-point 170°, Rhein dimethyl ether, C₁₄H₅O₂(OMe)₂2COOH, light-brown needles, melting-point 283-284°, Dimethyl rhein ethyl ester, C₁₄H₅O₂(OMe)₂COOEt, sulphur-yellow needles, melting-point 185-187°, Dimethyl rhein chloride, C₁₄H₅O₂(OMe)₂COCl, yellow prisms, melting-point 190°, Dimethyl rhein amide, C₁₄H₅O₂(OMe)₂CONH₂, plates, melting-point 287° (Robinson and Simonsen). The aminodimethoxy- anthraquinone and dimethoxy-anthraquinone alluded to above melt respectively at 243° and 204-205°.

RHEINOLIC ACID.

This compound, which is present in rhubarb root only in very small amount, was discovered by Tutin and Clewer (loc. cit.) in the mother liquor obtained during the purification of their emodin. Crystallised from pyridine it forms dark-red lustrous needles, which after drying at 130° melted between 295-297°.

Rheinolic acid, C₁₇H₁₀O₆, is a carboxylic acid containing at least one hydroxyl group, and when acetylated yields acetylrheinolic acid, small orange-coloured needles, melting at 236°, which readily dissolve in cold aqueous sodium carbonate. It is evidently an anthraquinone derivative, probably structurally related to rhein, and according to the above authors may contain a bridged ring. Alkaline solutions and concentrated sulphuric acid dissolve it with an intense red colour, and it is distinguished from rhein by the fact that addition of water does not precipitate it from its solution in the latter solvent.

ALIZARIN.

The presence of this substance in rhubarb root has been demonstrated by Hugo Muller (Chem. Soc. Trans., 1911, 96, 967) who isolated it from the residue which accumulates during the preparation of the officinal aqueous extract of rhubarb. This was extracted with benzene, and the product thus obtained fractionally crystallised from the same solvent. The alizarin in these circumstances is much less soluble than the emodin and chrysophanic acid which accompany it. The quantity present in the root is apparently minute.

Rhubarb, Aloe-Emodin(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.
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Bombay, Calcutta, and Madras
1918

()Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

ALOE-EMODIN.

Aloe-emodin appears to have been first isolated from rhubarb by Hesse (Pharm. J., 1895, iv., 1, 352, and Annalen, J 899, 309, 32), who described it as rhabarberon isomeric with emodin, C₁₅H₁₀O₅, and subsequently by Eyken who, though considering it as probably identical with Hesse's rhabarberon, termed it iso-emodin. More recent work by Oesterle has shown (Arch. Pharm,, 1899, 88) that historically the first preparation of this compound, though in an impure condition, is due to Tilden (Chem. Soc. Trans., 1877, 267), who under the name of aloe-chrysin obtained it by the oxidation of aloin (see later).

Tutin and Clewer (ibid., 1911, 948), on the other hand, first recorded aloe-emodin as a constituent of rhubarb root, and at the same time confirmed the identity of rhabarberon, iso-emodin, and aloe-emodin. According to Oesterle (loc. cit.) the emodin existing in senna is also aloe-emodin. Aloeemodin crystallises in pale brown orange needles melting at 223-224°, soluble in dilute ammonia to form a red-coloured liquid and in sulphuric acid with the same tint. These properties are identical with those of frangula-emodin, but on heating their solutions in sulphuric acid the product thus given by aloe-emodin dissolves in ammonia with a violet, whereas that from frangula-emodin gives a red coloration.

Acetylaloe-emodin, C₁₅H₅O₅(C₂H₃O₃, yellow needles, melts at 177-178° (Oesterle, Arch. Pharm., 1899, 237, (2), 81, 699), tripropionyl aloe-emodin, needles, at 152-153° (Oesterle), and tribenzoyl aloeemodin, greenish-yellow needles, at 23°4 (Robinson and Simonsen, Chem. Soc. Trans., 1909, 95, 1091). According to Leger (Comptes rend., 1910, 151, 128) tetranitroaloe-emodin, C₁₅H₆O₅(NO₂)₄, forms golden needles, melting-point 285°.

By the reduction of aloe-emodin with tin and hydrochloric acid in the presence of acetic acid, Oesterle (Schweiz. Wochenschr. f. Chem. u. Pharm., 1900, 21) obtained a compound crystallising in yellowish-green leaflets, melting-point 181-187°, which possessed the formula C₁₅H₁₂O₃ and was regarded as a dihydroxymethylanthranol.

By oxidation with chromic acid aloe-emodin is converted into rhein (Oesterle, Arch. Pharm., 1903, 241, 604), and when reduced chrysophanic acid is obtained (Oesterle, Arch. Pharm., 1911, 249, 455). The constitution of aloe-emodin is given on page 59.

Rhubarb, Frangula-Emodin Methyl Ether(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.
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1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

FRANGULA-EMODIN METHYL ETHER.

This compound, as already stated, is found associated with crude chrysophanic acid, and to its contamination with this impurity is to be ascribed the lower melting-point at first assigned to this latter substance. Originally isolated by Perkin and Hummel (Trans. Chem. Soc., 1894, 65,632) from the root- bark of the Ventilago madraspatana and by Perkin from the root of the Polygonum cuspidatum (ibid., 67, 1084), it was identified by Tutin and Clewer (ibid., 1910, 97, 1) as one of the constituents of the Rumex ecklonianus. Jowett and Potter (ibid., 1903, 77, 1330) who prepared this compound by the methylation of emodin doubted at first the identity of their product with the natural compound, but somewhat later Tutin and Clewer (loc. cit.) proved this to be the case.

It can be isolated (Oesterle and Johann, Arch. Pharm., 1910, 248, 476) by extracting the acetylated crude chrysophanic acid with alcohol at 50-55°, and hydrolysing the acetylemodin methyl ether thus produced, and has also been obtained (Tutin and Clewer) by a fractional extraction of the constituents of rhubarb root. The properties of this compound, which crystallises in orange-red needles, are described later in connection with the root-bark of the Ventilago madraspatana.

According to Oesterle and Johann this emodin methyl ether is identical with Gilson's rheo-chrysidin (Arch, internat. Pharm. Ther., 1905, 14, 492), with Hesse's physcion (lichen-chrysophanic acid) (Abst., 1906, 1, 280), and with the methyl-chrysophanic acid of this latter author (Abst., 1900, 1, 41).

Rhubarb, Emodin(CHAPTER I. The Anthraquinone 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.

EMODIN, C₁₅H₁₀O₅.

Emodin, the second important constituent of rhubarb root, is now known as frangula-emodin not only on account of its existence (in the form of glucoside) in the bark of the Rhamnus frangula, but to distinguish it from the isomeric aloe-emodin which can be obtained from rhubarb and other sources.

It was first isolated from rhubarb root by Warren de la Rue and Müller (Trans. Chem. Soc., 1857, 10, 300), who extracted the washed root with benzene, and treated the crude mixture of emodin and chrysophanic acid thus isolated with sodium carbonate solution, in which, in the cold, emodin only is soluble.

[---]

Emodin is contained as the glucoside frangulin in the bark of the Rhamnus frangula, the glucoside polygonin in the root of the Polygonum cuspidatum, and it has also been isolated from the R. purshianos and R. cuilludica (Tschirch and Pool, Arch. Pharm., 1908, 246, 315) and R. cathartica (Tschirch and Polacco, Arch. Pharm., 1900, 238, 459).