The constituents of hops / Frederick B. Power, Frank Tutin and Harold Rogerson.
- Frederick Belding Power
- Date:
- [1913?]
Licence: Public Domain Mark
Credit: The constituents of hops / Frederick B. Power, Frank Tutin and Harold Rogerson. Source: Wellcome Collection.
4/30 page 1268
![H. Bungener {Bull. Soc. chim., 1886, [ii], 45, 487) confirmed the observation of Lermer (loc. cit.) respecting the occurrence of a crystalline acid, insoluble in water, which rapidly became yellow and resinous on exposure to the air. He designated the substance “ lupulic acid,” stating it to melt at 92—93°, and to agree in composition with the formula C50H70O8. It was furthermore con¬ sidered that it is the resinous oxidation product of this acid which imparts bitterness to 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 C29H4GO10. This, when treated with dilute sulphuric acid, is said to be converted into a resinous product, “ lupuliretin,” C10H16O4, and a crystalline, bitter substance, “lupulinic acid,,” C48H82019, which is insoluble in water, the change being represented by the following equation: 2C29H46O10 + 3H20 = C10H16O4 + C48H82019. The same author, furthermore, assigns to hop-resin the formula C10H14O3, and assumes that by the simple addition of a molecule of water it is converted into “ lupuliretin,” C10H16O4. On the other hand, hop-resin, C10H14O3, is considered to be produced by the oxidation of the essential oil of hops, the latter being given the formula C10H18O, and the change represented as follows: C10H18O+ 202 —C10H14O3 + 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, C15H24, the fallacy of the above conclusions is apparent. Hayduck (Woch. Brau., 1887, 4, 397; 1888, 5, 937) has differentiated three resinous constituents of hops as follows: a-resin, which is soft, soluble in light petroleum, and precipitable by an alcoholic solution of lead acetate; /3-resin, which is similar to the preceding, but is not precipitable by lead acetate; and y-resin, which is a hard solid, insoluble in light petroleum, but soluble in ether or alcohol, and not precipitable by lead acetate. The solutions of both the a-resin and the /3-resin were said to be intensely and disagreeably bitter. Lintner and A. Bungener (Zeitsch. ges. Brauw.,1891,14, 357) note that in the a-resin of Hayduck (loc. cit.) crystals were formed after some time which appeared to be different from H. Bungener’s hop-.](https://iiif.wellcomecollection.org/image/b30620387_0004.jp2/full/800%2C/0/default.jpg)
