H. Bungener (BzLZZ. SOC. chim., 1886, [ii], 45, 487) confirmed the observation of Lermer (Zoc. cit.) respecting the occurrence of a crystalline acid, insoluble in water, which rapidly became yellow and resinous on exposure t o the air. H e designated the substance "lupulic acid," stating it to melt a t 92-93*, and to agree in composition with the formula C50H7008. It was furthermore considered that it is the resinous oxidation product of this acid which imparts bitterness t o a decoction of hops, and that this resinous product exists in hops together with the acid from which it is readily formed. Bungener and Fries (Zeitsch. ges. Brauw., 1885, 8, 267) have stated that hops contain asparagine, but although the method of separation was given, no analysis or other evidence of the identity of the substance appears to have been recorded. Issleib (Arch. Pharm., 1880, 13, 345), from the results of a somewhat extended investigation, has concluded that hops contain a peculiar bitter substance, " hop-bitter," of the composition C29H4,0,0. This, when treated with dilute sulphuric acid, is said to be converted into a resinous product, " lupuliretin," C10H1604, and a crystalline, bitter substance, " lupulinic acid,," C,,H8201,, which is insoluble in water, the change being represented by the following equation : 2C29H46010 + 3H20 =C10H1604 f C48H82019* The same author, furthermore, assigns to hop-resin the formula Cl0HI4O3, and assumes that by the simple addition of a molecule of water it is converted into " lupuliretin," C,,H160,. On the other hand, hop-resin, C10H1403, is considered t o be produced by the oxidation of the essential oil of hops, the latter being given the formula CloH180, and the change represented as follows : C1oH180 + 2 0 , = C,,Hl40, + 2H2O. Inasmuch as it is well known, however, that both hop-resin and the essential oil of hops are very complex products, the latter consisting largely of a sesquiterpene, Cl5HZ4, the fallacy of the above conclusions is apparent.
TUTIN AND CLEWER: THE CONSTITUENTS OF RHUBARB. 947 a product called " rhabarberin." This wm shown by Schlossberger and Dijpping (Annulen, 1844, 50, 214) t o be identical with chrysu phanic acid, which had, in the meantime, been described by Rochleder and Heldt, but it would appear probable that it was a mixture of this compound and emodin monomethyl ether. De la Rue and Miiller (Journ. Chem. SOC., 1857, 10, 298) examined a deposit from " Extracturn Rhei," from which they obtained " chrysophane " and a new compound, designated its emodin. Heme (Pharm. J., 1895, [iv], I, 352; and ,4nnaZen, 1899, 309, 32) recorded the occurrence in rhubarb of rhein and "rhabarberon" (an isomeride of emodin), but was unable to isolate pure chrysophanic acid, this being always associated with a methylated constituent, which wm assumed t o be a methyl ether of chrysophanic acid. The next communication of importance on Chinese rhubarb was by Tschirch and Heuberger (Arch. Pharm., 1902, 204, 596), who failed to obtain the " rhabarberon " of Hesse, but isolated gallic acid, a substance giving the reactions of a cholesterol, impure chrysophanic acid, emodin, rhein, and two amorphous, glucoeidic products, namely, rheotannoglucoside and rheomthraglucolside. The former of these products, on hydrolysis, gave a laevorotatory sugar and small amounts of gallic and cinnamic acids, together with amorphous products, whilst the latter " glucmide " yielded a dextrorotatory sugar, small amounts of the acids mentioned, a mixture of anthraquinone derivatives, and amorphous material. Eyken (Phwm. V'eekblad, 1904, 41, 177) isolated impure chrysophanic acid, emodin, " isoemodin," and rhein, together with (' anthraglucwides," and Tschirch and Eyken (Schweiz. Woch. Pharm., 1904, Nos. 40 and 41) stated that " isoemodin " is probably identical with Hesse's " rhabarberon." Gilson (Compt. rend., 1903, 136, 385) claimed to have isolated two crystalline glucmides, '(glucogalline " and " t 6 t r a h e. " The former of these was stated t o yield dextrose and gallic acid, whilst the latter gave the same sugar, gallic and cinnamic acids, and " rh6usmine." Quite recently, Oesterle and Johann (Arch. Pharm., 1910, 248, 476) showed in an indirect way that the methylated substance with which the chrysophanic acid from rhubarb is invariably wociated was emodin monomethyl ether, identical with that wociated with chrysophanic acid in Rurnex Ecklonianus, Meisaner (Tutin and Clewer, Trans., 1910, 97, 1). I n addition to the compounds mentioned in the foregoing review of the literature, most of the abovementioned investigators also describe, under various names, a number of amorphous products, which were obviously of indefinite composition. Mention is several times made, however, of the presence in rhubarb of ((glucose " and of a neutral fat.
By FREDERICK BELDING POWER and FRANK TUTIN. THE bark of the olive tree, Olea Europaea, LinnB, is reputed to posses8 medicinal properties similar t o those of the leaves, but, with the exception of the observation that, like other parts of the plant, it contains mannitol, nothing appears to have been ascertained respecting
By FREDERICK BELDING POWER and FRANK TUTIN. QUERCITOL has hitherto only been found in the fruits (acorns) of certain species of Quevcus, in which it exists as a dextrorotatory modification. The laevorotatory modification now described was obtained by us from the leaves of Gymn.ema sylvesti-e (Br.), a plant belonging to the family of Asclqhatlacece, and indigenous to Banda and the Deccan-Peninsula (compare Pharmacographia Indica," vol. 11, p. 450). In the course of a n examination of a large quantity of Gymnema leaves, a colourless, crystalline substance having the empirical formula CGH,,06 was isolated, which melted a t 1 7 4 O and had [a].-73.9'. When heated at l l O o , it lost one molecular proportion of water; i t formed a penta-acetyl derivative, C,Hp(OoC,H,0)5, and a pentabenzogl derivative, C,€l,(O*C,H,O),. From these facts i t was seen that the above formula, C6Hl4O6, could be appropriately modified to C6H1(OH),,H,0, which represents the substance as a hydrated isomeride of quercitol. The constitutional formula of quercitol, first proposed by Kanonnikoff, represents it as pentahydroxyhexahydrobenzene, Y? HO*HC C€€*OH HO~HC CEPOH \/ C'H*OH The correctness of this formula was proved by Kiliani and Schaefer (Ber., 1896, 29, 1762), who obtained malonic acid on oxidation with potassium permanganate. Moreover, the same investigators have shown that d-quercitol, on oxidation with aqueous bromine, forms a diketone, CGHSO,, which was isolated in the form of its dihydrazone, The substance isolated from the leaves of Gprnnerncc sylvestre, when oxidised with potassium permanganate and sodium hypobromite respectively, showed a behaviour identical with that of d-quercitol. Like the latter, i t afforded, on the one hand, malonic acid, and, on the other, a diketotrihydroxyhexahydrobenzene, which was isolated in the form of its dihydrazone (m. p. 209'). It was thus demonstrated that our substance has the same constitution as d-quercitol, and can only ditfer from the latter stereo C1SH2003N4'
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