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GLUCOSIDE

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Originally appearing in Volume V12, Page 143 of the 1911 Encyclopedia Britannica.
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GLUCOSIDE , in See also:

chemistry, the generic name of an extensive See also:group of substances characterized by the See also:property of yielding a See also:sugar, more commonly See also:glucose, when hydrolysed by purely chemical means, or decomposed by a ferment or See also:enzyme. The name was originally given to See also:vegetable products of this nature, in which the other See also:part of the See also:molecule was, in the greater number of cases, an aromatic aldehydic or phenolic See also:compound (exceptions are sinigrin and jalapin or scammonin). It has now been extended to include synthetic See also:ethers, such as those obtained by acting on alcoholic glucose solutions with hydrochloric See also:acid, and also the polysaccharoses, e.g. See also:cane sugar, which appear to be ethers also. Although glucose is the commonest sugar See also:present in glucosides, many are known which yield rhamnose or iso-dulcite; these may be termed pentosides. Much' See also:attention has been given to the non-sugar parts of the molecules; the' constitutions of many have been determined, and the compounds synthesized; and in some cases the preparation of the synthetic glucoside effected. The simplest glucosides are the alkyl See also:esters which E. See also:Fischer (Ber., 28, pp. 1151, 3081) obtained by acting with hydrochloric acid on alcoholic glucose solutions. A better method of preparation is due to E. F. See also:Armstrong and S. L.

Courtauld (Proc. Fischer found that maltase, an enzyme occurring in yeast 0 cells, hydrolysed a-glucosides but not the 0; while emulsin, H C OCH3 CH30 C .H an enzyme occurring in See also:

bitter I. a-methyl II. 0-methyl d almonds, hydrolyses the (3 glucoside dglucoside. but not the a. The ethers of non-fermentable sugars are them-selves non-fermentable. By acting with these enzymes on the natural glucosides, it is found that the See also:majority are of the 0-See also:form; e.g. emulsin hydrolyses See also:salicin, helicin, aesculin, coniferin, syringin, &c. See also:Classification of the glucosides is a See also:matter of some difficulty. One based on the chemical constitution of the non-glucose part of the molecules has been proposed by Umney, who framed four See also:groups: (I) See also:ethylene derivatives, (2) See also:benzene derivatives, (3) See also:styrolene derivatives, (4) See also:anthracene derivatives. A group may also be made to include the cyanogenetic glucosides, i.e. those containing prussic acid. J. J. L. See also:van Rijn (See also:Die Glykoside, r9oo) follows a botanical classification, which has several advantages; in particular, See also:plants of allied genera contain similar compounds.

In this See also:

article the chemical classification will be followed. Only the more important compounds will be noticed, the reader being referred to van Rijn (loc. cit.) and to Beilstein's Handbuch der organischen Chemie for further details. I. Ethylene Derivatives.—These are generally See also:mustard See also:oils, and are characterized by a burning See also:taste; their See also:principal occurrence is in mustard and Tropaeolum seeds. Sinigrin or the See also:potassium See also:salt of myronic acid, C,0H16NS2KO9•See also:H2O, occurs in See also:black See also:pepper and in See also:horse-See also:radish See also:root. See also:Hydrolysis with baryta, or decomposition by the ferment myrosin, gives glucose, allyl mustard oil and potassium bisulphate. Sinalbin, C30H42N2S2015, occurs in See also:white pepper; it decomposes to the mustard oil HO•See also:C6H4•See also:CH2•NCS, glucose and sinapin, a compound of choline and sinapinic acid. Jalapin or scammonin, C84H66O16, occurs in See also:scammony; it hydrolyses to glucose and jalapinolic acid. The formulae of sinigrin, sinalbin, sinapin and jalapinolic acid are: C6H1105'S'CGO•SO2.OK C61-11105S C< ON.SOCH02C 6H24O N Sinigrin Sinalbin (CH3IO))22>CGH•CH:CH CO C2H4 O N<(CCH3)3 Sinapin C213>CH•CH(OH) •C1oH20.0O2H. Jalapinolic acid (Kramer) 2. Benzene Derivatives.—These are generally oxy and oxyaldehydic compounds. Arbutin, C12H1507, which occurs in bearberry along with methyl arbutin, hydrolyses to hydroquinone and glucose.

Pharmacologically it acts as a urinary antiseptic and diuretic; the benzoyl derivative, cellotropin, has been used for See also:

tuberculosis. Salicin, also termed " saligenin " and " glucose," C13H1807, occurs in the See also:willow. The enzymes ptyalin and emulsin convert it into glucose and saligenin, ortho-oxybenzylalcohol, . HO • See also:C6H 4• See also:CH2OH. Oxidation gives the aldehyde helicin. Populin, C20H2208, which occurs in the leaves and bark of Populus tremula, is benzoyl salicin. 3. Styrolene Derivatives.—T his group contains a benzene and also an ethylene group, being derived from styrolene See also:C6H5•CH:CH2. Coniferin, C16H2208i occurs in the cambium of coniferous See also:woods. Emulsin converts it into glucose and coniferyl See also:alcohol, while oxides tion gives glycovanillin, which yields with emulsin glucose and vanillin (see See also:EuGENoL and See also:VANILLA). Syringin, which occurs in the bark of Syringa vulgaris, is methoxyconiferin. Phloridzin, C21H24010, occurs in the root-bark of various See also:fruit trees; it hydrolyses to glucose and phloretin, which is the phloroglucin ester of paraoxyhydratropic acid.

It is related to the pentosides naringin, C21H26011, which hydrolyses to rhamnose and naringenin, the phloroglucin ester of See also:

para-oxycinnamic acid, and hesperidin, Phys. See also:Soc., 1905, See also:July 1), who dissolve solid anhydrous glucose in methyl alcohol containing hydrochloric acid. A mixture of a- and 13-glucose result, which are then etherified, and if the See also:solution be neutralized before the 0-form isomerizes and the solvent removed, a mixture of the a- and '3-methyl ethers is obtained. These may be separated by the See also:action of suitable ferments. Fischer found that these ethers did not reduce See also:Fehling's solution, neither did they combine with phenyl See also:hydrazine at roo°; they appear to be stereo-isomeric 7-oxidic compounds of the formulae I., II.: The difference between the a- and 0-forms is best shown by the CH2OH CH2OH selective action of enzymes.

End of Article: GLUCOSIDE

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