ORGANIC SUBSTANCES OF UNKNOWN CONSTITUTION.

1214. Numerous organic substances, many of them well defined, have been prepared from animals and vegetables, but so far there is not enough known of their chemical behaviour, decomposition products, &c., to afford proof of their composition.

By far the largest number of these contain radicals nearly allied to the aromatic compounds, and which indeed often yield well-known benzene derivatives when the decomposition is carried further; they cannot, however, be arranged in a rational system.

In the following pages such glucosides, acids, indifferent crystallisable vegetable substances (colouring matters and bitter principles), resins, alkaloids, tannins, and proteïds as are of sufficient importance will be described.

GLUCOSIDES.

1215. Under the term glucosides are comprehended ethereal derivatives of the sugars, especially of grape sugar (comp. § 870); they are mostly of natural origin. By the action of dilute mineral acids, and of certain organic substances acting as ferments, they are split up into the sugar, and as a rule only a single other compound.

They are obtained by heating the vegetable matter with hot water or alcohol. The more easily soluble glucosides cannot be thoroughly separated by simple crystallisation from the accompanying substances, such as tannin. In order to remove these latter the solution is treated with neutral plumbic acetate, the lead precipitated from the filtrate by sulphuretted hydrogen, and the filtrate from which the colouring matters have generally been removed by the above processes evaporated to the crystallising point. The constitution of many glucosides is not known, so that formulæ cannot be always assigned to them.

Among the more important glucosides arbutine, salicine, populine, phloridzine, ruberythric acid, and franguline have been described in detail, and amygdaline and myronic acid at least mentioned.

Vegetable Glucosides.

1216. Amygdaline, C20 H27NO11, is the crystallisable bitter principle of bitter almonds. It can be extracted from the meal, which has been pressed as much as possible to remove fat, by means of boiling alcohol. On evaporating the filtrates considerably the amygdaline crystallises out, and is then purified by washing with ether and recrystallising from hot alcohol. Amygdaline is easily soluble in water and hot alcohol.

From the latter it crystallises in pearly scales, from the former in prisms containing three molecules of water of crystallisation. On gently warming with acetic anhydride it forms a heptacetate :

C20H20(C2H3O),NO11,

which crystallises in silky needles from alcohol and ether. Aqueous solutions of amygdaline are decomposed by the ferment emulsin into sugar, hydrocyanic acid, and benzoic aldehyde (§§ 74 and 1031). On long boiling with baryta water ammonia is evolved and the baryta salt of amygdalic acid, C20H28013, is formed. The acid is crystalline and deliquescent in moist air. Amygdaline occurs also in the kernels of stone fruit, in the leaves of the cherry laurel (Prunus Laurocerasus), and in many other amygdalaces and pomaceæ.

1217. Esculine, C5H1609,2H2O. Esculine occurs, together with a little fraxine, in the bark of the horse chestnut (Aesculus hippocastanum). If the aqueous extract of the bark be precipitated with plumbic acetate and the excess of lead removed by sulphuretted hydrogen, on evaporating the filtrate aesculine crystallises out mixed. with a little fraxine, which latter dissolves first on warming the crystalline magma with water. Æsculine crystallises in colourless needles, which have a faint bitter taste and dissolve difficultly in cold water, easily in hot water and in alcohol.

At about 110° they lose water and at 160° they melt, losing more water. The aqueous solution has a strong blue fluorescence, which disappears on acidifying, but appears again on adding an alkali. Treated with acetic anhydride it yields a hexacetate :

C15H10(C2H3O)609,

which crystallises in needles and melts at 130°. It is split up by emulsin or dilute acids into sugar and æsculetine, C„H¿О4,Ĥ2O :

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Esculetine occurs ready formed in small quantity in the bark of the horse chestnut. It crystallises with one molecule of water in needles or plates, melts at 270°, and is only soluble with great difficulty in water or alcohol. It is readily soluble, with yellow coloration, in alkalies, and yields with acetic anhydride a triacetate :

C9H3(C2H30)3043

this latter crystallises in silky needles. Hot concentrated solution of potassic hydrate decomposes æsculetine into oxalic, formic, and protocatechuic acids.

Daphnine, isomeric with æsculine, is a glucoside occurring in the bark of many species of daphne (D. alpina, D. mezereum). It also crystallises in prisms (with 20H,) and on decomposition yields daphnetine, C,H604,H,Ò. This latter loses water at 220° and then sublimes. It yields a monacetyl derivative, C,H3(C2H3O)O4, m.p. 129°-130°.

1218. Fraxine, C27H30O17(?), is found together with æsculine in the bark of the horse chestnut, especially in the winter, but occurs in larger quantity in ash bark (Fraxinus excelsior), from which it can therefore be most profitably extracted. After precipitating

the tannins from the aqueous extract by means of neutral plumbic acetate the fraxine can be thrown down by basic lead acetate and the precipitate suspended in water and decomposed by sulphuretted hydrogen. It crystallises from the filtrate in fine colourless needles grouped in bunches, which only dissolve abundantly in boiling water or alcohol and fuse at a strong heat.

Dilute acids split it up into sugar and fraxetine :

C27H30O17+ 3H20=2C6H1206 + C15H12O8 (?).

The fraxetine separates out in colourless needles soluble in alcohol. It dissolves in nitric acid, giving first a violet, then red, and lastly yellow colour.

1219. Quercitrine, C33H30017. Quercitrine is the glucoside of quercitron, the bark of Quercus tinctoria. It occurs also in other plants, such as in sumach, grape vine, and in catechu. The respective substances are extracted with alcohol and the tannin precipitated by means of gelatine solution. On evaporating the filtrate small yellow crystals of quercitrine are obtained, which are but slightly soluble in hot water. Dilute acids split up quercitrine into isodulcite (§ 853) and quercetine, C27H18012:

C33H30017 + H2O = C6H1406 + C27H18012.

Quercetine occurs ready formed in other plants, such as tea, bark of the apple tree, &c. Separated from its solutions it forms a yellow crystalline powder, which may be partially sublimed in beautiful yellow needles.

It is readily soluble in alcohol, also in alkalies, with which it forms crystalline compounds. It is coloured green by ferric chloride. Hot and very concentrated alkali solutions decompose it into phloro-glucine (§ 1000) and quercetic acid, which crystallises in fine prisms, and by fusing with alkalies is decomposed into various substances, amongst which may be mentioned paradatiscetine, C15H1006, crystallising in fine yellow needles; quercimeric acid, C,H,O,H20, which crystallises in thick prisms and gives a fine blue colour with ferric chloride; and as a final product protocatechuic acid, C-H6O.

The following are very similar to quercitrine :

Rutine, occurring in Ruta graveolens and the flower buds of Capparis spinosa (capers); it yields quercetine on decomposition.

Datiscine, occurring in the roots of Datisca cannabina, which is used in the East as a yellow dye for silk; it yields sugar and datiscetine on decomposition.

Robinine, from the flowers of Robinia pseudacacia, yields quercetine when boiled with dilute acids.

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1220. Convolvuline and Jalapine. The roots of jalap (the rhidzomes of Convolvulus Schiedanus and C. orizabensis) contain as the active principles two amorphous glucosides in the first convolvuline, in the others jalapine, which belong to the same homologous series, since their compositions not only differ by C3H, but also yield homologous products on decomposition. In order to prepare them the jalap roots must be several times extracted with water, and then with alcohol, the colour removed by animal charcoal, and the filtrate evaporated down on the water bath. The residue is then treated with alcohol and the glucosides precipitated by ether.

Convolvuline, C3, H50016, and jalapine, C34H56016, are amorphous, colourless and odourless masses, slightly soluble in water, very easily soluble in alcohol and in dilute acids, not at all in ether; they act as purgatives. On heating they fuse (convolvuline fuses at 150°), and are decomposed at a rather higher temperature. They are dissolved by strong bases, forming the salts of the easily soluble acids convolvulic acid, C3H52017, and jalapic acid, C3H58O17. These acids are most easily prepared by boiling the original glucosides with baryta water, and, after accurately precipitating the barium with sulphuric acid, evaporating the filtrate, when they are obtained as easily soluble, amorphous bodies, melting a little above 100°. The salts, whether containing one or two equivalents of metal, are also amorphous.

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The original bodies or the acids are decomposed by emulsin, yielding sugar. Convolvuline gives at the same time convolvulinol:

2C13H2403, H2O,

jalapine similarly yielding jalapinol, 2C16H30O3,H2O:

C31H50016 + 50H2 = C13H24O3 + 3C6H12O6.

Both crystallise in indistinct cauliflower-like masses, are insoluble in water, soluble in alkalies, giving salts of convolvulinolic acid, C13H26049 and jalapinolic acid, C16H3204. These acids are difficultly soluble in water, and are therefore precipitated on acidifying solutions of the salts. They both form fine crystalline masses, feeling fatty when touched; the salts are crystalline. Convolvulinolic acid melts at 40°50°, jalapinolic acid at 64°. Nitric acid oxidises them to ipomic acid, isomeric with sebacic acid.

Jalapine occurs also in scammony resin, the hardened juice of Convolvulus Scammonia. An isomeric body, turpethine, is found in turpeth resin (from the roots of Ipomoea Turpethum); it yields amorphous turpethic acid, C34H60O18, when treated with baryta water, and is decomposed on boiling with dilute acids into sugar and amorphous turpetholic acid, C16H3204.

Convolvulinolic, jalapinolic, and turpetholic acids, having the general formula CnH2nO4, are apparently homologues of glyceric acid; at all events they do not belong to the aromatic series.

1221. Saponine, C32H51O18 (?), is found in many plants-for instance, in the kinds of lychnis (Lychnis Gythago), in the roots of Polygala senega, &c., but especially in the roots of Saponaria officinalis.

By boiling the latter with alcohol and cooling the hot filtrate it is obtained in colourless amorphous masses. It is rather soluble in water, forming a solution which behaves like soap solution when shaken; it is only slightly soluble in cold alcohol, not at all in ether. It is poisonous and its dust causes violent sneezing. It is split up by strong HCl into an uncrystallisable sugar and sapogenine, C14H2204 The latter forms white, difficultly soluble crystals.

1222. Chinovine, C3H4808, is a constituent of many cinchona barks, especially of China nova and of tormentil roots. From the former it may be prepared by extracting repeatedly with water, treating with milk of lime, and precipitating the filtered solution with hydrochloric acid. The precipitate must be redissolved in alcohol and

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1223. Glycyrrhizine, CH2Oμ occurs in bi arise root flyer rhiza glina, from which it may be extracted by holing wate. is then precipitated by prozne wstate and the praspitate ragendei in water, despoed vy szjarretsi bșirea on ensporate of the wolation the z. verrri.zine is left as a light yellow amorphous powder. which at first thetes sweet and afterwards has an initating efect Bling diste actis decompose it into a sugar and glycyrrhetime,

1224 Helleborene, CHO, is obtained from the roots of Helleborus niger, and also from H. viridis, but in smaller quantity, in the form of microscopic colouries relles, rally soluble in water. diffenitly in alcohol. On boiling with dilute acids it yields sugar ani helleboreting, CH,O,, which is at first violet blue, but becomes greyish green after drying.

Helleboring, a substance crystallising in colourless concentrically grouped needies, also occurs in quantity in Helleborus viridis, but only sparingly in H. niger. It is insoluble in water, readily soluble in alcohol, and is coloured intensely red by strong sulphuric acid Boiling dilute acids convert it into sugar and amorphous helleboresine, CH,O,. Both glucosides act as narcotics, especially helleborine.

1225. Digitaline is the bitter, highly poisonous constituent of Digitalis purpurea. It is almost insoluble in water, readily soluble in alcohol and chloroform. On heating with concentrated phosphoric and hydrochloric acids it gives an intense green colour; boiling dilute sulphuric acid converts it into sugar and resinous digitalretine.

Antiarine, CHO, is extracted by alcohol from the Indian arrow poison, Upas antiar, the dried milky juice of Antiaris toxicaria, and is obtained on evaporation in colourless crystalline leaves, melting at 220; the melted mass becomes amorphous on cooling. Antiarine is soluble both in water and ether, and when introduced into a wound it acts as a violent poison. It is split up by dilute mineral acids into sugar and a resinous body.

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1226. Carminic acid, C17H1010, is found in many plants-for instance, in the blossoms of Monarda didyma-but especially in cochineal, the female of Coccus cacti. The pulverised insects must be extracted with boiling water, the filtrate treated with plumbic acetate, and the washed precipitate suspended in water and decomposed by hydric sulphide. The filtered solution, when evaporated, leaves the acid as a purple red amorphous mass, which yields with bases salts of the same colour. By boiling with dilute acid it yields an optically inactive sugar, which is amorphous and not capable of fermentation, and the dark purple carmine red, C11H1207, soluble in water and alcohol. Carmine red heated with strong nitric acid yields oxalic acid and nitrococcio acid, CgH5(NO2)303, crystallising in yellow tables, probably a trinitro-cresotic acid (§ 1080). Similar valuable red