Olibanum (or Frankincense) is a gum-resin exuding from the several species of Boswellia in Eastern Africa and Southern Arabia. It contains from 4 to 7 per cent. of essential oil, from 56 to 72 per cent. of resin, and about 30 per cent. of gum. When burned it develops a strongly aromatic odor.

Myrrh (Myrrha, U. S. P.) is a gum-resin exuding from the Commiphora Myrrha in Eastern Africa and Southwestern Arabia. It contains from 2 to 4 per cent. of volatile oil, from 25 to 40 per cent. of resin, and from 40 to 60 per cent. of gum. Fused with caustic potash the resin yields pyrocatechin and protocatechuic acid. It is used extensively in the form of tincture and powders.

Bdellium is a gum-resin very similar in character to myrrh.

Gamboge (Cambogia, U. S. P.) is a gum-resin exuding as a milky juice from incisions in Garcinia Hanburii, and is collected in bamboo joints, and comes into commerce in cylindrical pieces. It forms a yellow emulsion with water. It contains 16 to 26 per cent. of gum, 66 to 80 per cent. of resin or cambogic acid, and about 4 per cent. of wax.

Euphorbium is an exudation from incisions in the stem of the Euphorbia resinifera from Morocco. It contains 18 per cent. of gum, 38 per cent. of resin, some starch, malates, and ash.

Scammony (Scammonium, U. S. P.) is a milky juice collected in Western Asia from the Convolvulus Scammonia. It

34

forms a greenish emulsion with water. It contains from 75 to 90 per cent. of resin, known as scammonin, СH58O18, identical with the orizabin of Ipomea orizabensis, and converted by alkalies into scammonic acid, which is soluble in water. The rest of the drug is gum, soluble in water.

CHAPTER X.

GLUCOSIDES-BITTER AND NEUTRAL PRINCIPLES.

I. GLUCOSIDES.

UNDER this name have been grouped a number of compounds, occurring mainly in the vegetable kingdom, that under the influence of dilute acids or ferments are split up into component parts, of which glucose or a related carbohydrate always is one. The glucosides appear to be, not esters, but ethers, which, under the treatment above referred to, take up the elements of water, and then yield the glucose and other products.

While sharing this method of decomposition in common they show in other respects a wide divergence. Thus, solanin is a nitrogenous base, and is thus at once an alkaloid and a glucoside, while other glucosides, like myronic acid, are of well-defined acid character. The most of the glucosides, however, are neutral bodies, although they frequently combine with metallic oxides, such as lead and mercuric oxides. They are usually soluble in water and in alcohol, often insoluble in ether, and generally crystallizable. On heating with concentrated sulphuric acid and the bile acids, the glucosides give, like the sugars, the Pettenkofer bile reaction,-viz., a deep-red color. Alkaline copper solution is reduced by most, but not all, of the glucosides. Ammoniacal silver solution is reduced by glucosides, as by canesugar and mannite, only after the addition of caustic alkali. Many glucosides are optically active, most of them showing a lævo-rotatory character. This rotatory power does not, however, correspond in any way to that of the sugar, which is obtained by the decomposition of the glucoside.

Glucosides, as a rule, are not decomposed by pure water, even on boiling or heating under pressure, but dilute acids readily effect the decomposition, sulphuric and hydrochloric being chiefly used. Alkalies may also effect the decomposition, although baryta water is better adapted, as the stronger alkali generally acts upon the sugar liberated, decomposing or altering it. splitting up of the glucosides is, however, often best effected by the action of ferments, which may act at the ordinary or only slightly elevated temperature. Among such ferments may be

The

mentioned emulsin, an albuminoid found in the almond; myrosin, found in mustard-seed; and the ferment contained in the saliva.

For the extraction of glucosides from the plant it frequently suffices to extract with water or alcohol, and to crystallize the glucoside from the concentrated extracts after decolorizing with animal charcoal; or, after defecating the decoction from the plant with neutral acetate of lead, which does not affect the glucoside as a rule, the addition of basic lead acetate will precipitate it in the form of a weak combination readily decomposed by hydrogen sulphide. Tanret has proposed still another procedure. After leaving the finely-pulverized plant material in contact with milk of lime for 24 hours, he extracts with distilled water in a displacement apparatus, and precipitates these extraction liquors with a concentrated solution of sodium chloride; the precipitate is dried, preferably in vacuo, and extracted with chloroform, which dissolves the glucoside, which can then be crystallized out. The first successful synthesis of a natural glucoside was accomplished by Arthur Michael in 1879, who caused acetochlorhydrose (obtained by the action of acetyl chloride upon glucose) to act upon the potassium compound of salicyl-aldehyde in alcoholic solution, when helicin was formed, and this, by the action of sodium amalgam, was converted into salicin. The same synthesis led to the formation of populin (benzoyl-salicin), and the corresponding reaction of acetochlorhydrose upon the potassium compound of methyl-hydroquinone led to the synthesis of methyl-arbutin, another naturally occurring glucoside. A newer and much more generally applicable method for the synthesis of the glucosides has been recently announced' by Emil Fischer. He finds when glucose and other sugars of the monosaccharide class (see p. 633) are dissolved in an alcohol, and hydrochloric acid gas is passed in, there forms a glucoside or mixed ether with the elimination of water. This reaction seems to be available for all the alcohols; in the case of glucose it has been proved with methyl, ethyl, propyl, isopropyl, amyl, allyl, and benzyl alcohols, as also with ethylene glycol and glycerin. It may even be employed for the hydroxy-acids (alcohol-acids), as was proved by the preparation of lactic glucoside. Where the sugar is completely insoluble in the alcohol, which is the case with many compounds of the aromatic and terpene series, in place of glu

1 Berichte der Chem. Ges., 1893, p. 2400.

cose, acetochlorhydrose, or pentacetyl-glucose, may be employed, as both are soluble in ether, benzene, and chloroform. As the bioses (cane- and milk-sugar and maltose) are hydrolyzed by hydrochloric acid, they cannot be converted in this way into glucoside-like compounds. These new artificial glucosides, like the natural ones, are unattacked by boiling alkalies, Fehling's solution and phenyl-hydrazine; if, however, they be heated with dilute acids they are readily hydrolyzed into their components. They are likewise hydrolyzed by the invertase of yeast.

The glucosides which are of more especial pharmaceutical or medical importance are the following:

Amygdalin, CH27NO11-3H2O, is found in bitter almonds and in the kernels of fruit. It is extracted by alcohol from the compacted cake of the almond after the oil has been pressed out. It forms a white, crystalline powder, of slightly bitter taste, melting at 200°. When boiled with dilute acids, or when the aqueous extract of the bitter almond is digested at 25°-35°, it is decomposed according to the reaction:

C20H27 NO11 + 2H2O = CH2O + CNH+2C6H12O6 the products being benzaldehyde, hydrocyanic acid, and dextrose. In the latter case the decomposition is brought about by the emulsin, or soluble ferment, which occurs in both the sweet and the bitter almond.

Esculin, C15H1809.11⁄2HO, is found in the bark of the horse-chestnut. It forms prisms of a bitter taste, melting at 160°, and is decomposed by boiling with dilute acids or by emulsin into glucose and æsculetin (dioxycoumarin) :

C15H18O9+ H2O = C8H1208 + СH ̧О.

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Arbutin, C12H1807. H2O, and Methyl-arbutin, C13H18O7, are contained in Arbutus Uva-ursi and Chimaphila umbellata and other ericaceous plants. Both are bitter, crystallizable principles, separable only with difficulty. Both are decomposed by dilute acids or emulsin, the former into glucose and hydroquinone, and the latter into glucose and methyl-hydroquinone.

Carminic Acid, C17H18O10, is the coloring constituent of cochineal (the dried female insect Coccus cacti), and the essential constituent of the commercial "carmine," obtained by extracting the cochineal with water and precipitating with alum. It is an amorphous, purplish-red mass, soluble in water and alcohol, which on boiling with dilute acids is decomposed as follows: C17H18010+ 2H2O = CH12O7+ CH1005 Carmine-red. Carmine-sugar.

Cerebrin is a nitrogenous glucoside contained in brain- and nerve-tissue. On boiling with dilute sulphuric acid it yields galactose (cerebrose).

Chitin, C15H26N2O10, is another animal glucoside found in the outer shells of the Crustacea. It is an amorphous substance, which when boiled with strong hydrochloric acid is decomposed into acetic acid and glycosamine, C8H1105.NH2.

Coniferin, CH22Og. 2H2O, is a glucoside found in the cambial juice of the Conifera and in the woody tissue of the sugar-cane. It is decomposed by emulsin into glucose and coniferyl-alcohol, according to the reaction:

C18H22O8+ H2O = C10H12O3 + C8H12O6

When oxidized with chromic acid mixture coniferin yields vanillin (see p. 718). On the other hand, if oxidized by weaker agents, like potassium permanganate, the coniferin is changed into gluco-vanillic acid, C14H18O,, and gluco-vanillin, C11H18O8By the action of emulsin or dilute mineral acids, these artificial glucosides are split up into glucose and vanillic acid, or vanillin, as the case may be.

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Convolvulin, C4H56O16, and Jalapin, C ̧1H50O16, are two glucosides contained in jalap resin, the former chiefly obtained from Ipomea orizabensis (Mexican male jalap), and the latter from Ipomea Jalapa. When jalap resin is boiled with dilute sulphuric acid some time and filtered, we obtain a mixture of jalapinol, C13H2O3, and convolvulinol, C18H3003

Digitalin. The leaves of the foxglove (Digitalis purpurea) yield several medicinally active principles which are glucosides, but the true composition of which seems still to be a matter of controversy.

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The French or crystalline preparation, difficultly soluble in alcohol, seems to consist chiefly of digitoxin, C21H2O7, which is not a glucoside. On the other hand, the German preparation is amorphous and easily soluble in alcohol. It contains digitonin, CgHs,Oz, digitalein, CanHOg, and digitalin, (C,H,O,).. The first of these breaks up on boiling with dilute acids into sugar and two compounds, digitoresin and digitonein; the second and the third both break up into glucose and digitaliresin.

31 52 17,

22

8

Frangulin, C21H20O10, is a glucoside found in the bark of Rhamnus frangula. It is decomposed on hydrolysis into rhamnose, CH1205, and emodin (trioxymethyl-anthraquinone), C15H1005

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Glycyrrhizin, C44H8NO18, is found in liquorice-root (Glycyrrhiza glabra) as the acid ammonium salt, C4H82(NH4)NO 18.