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.
5/30 page 1269
![bitter acid (loc. cit.). They obtained a crystalline product, melting at 56°, which showed but little tendency to resinify, and this was supposed to be identical with the bitter substance of Lermer. Seyffert and von Antropoff (Zeitsch. ges. Brauw., 1896, 19, 1), in an attempt to compare the products obtained by them with those of other investigators, were led to conclude that hop resins are mixtures of substances in a state of progressive decomposition. Barth (Zeitsch. ges. Brauw., 1900, 23, 509, 537, 554, 572, 594), who has reviewed the results of earlier investigators, states that the formula of lupulic acid is not C50H70O8, as given by H. Bungener (loc. cit.), but C25H3604, and that there is no doubt of its identity with Lermer’s bitter acid. On oxidation with permanganate, it gave valeric acid. He also indicates that the so-called lupulic acid does not contain a carboxyl group, since it can be recovered from an alkaline solution by extraction with ether. On the other hand, it is stated that when fused with potassium hydroxide, it yields a hydrocarbon having a density of 0'8840 at 15°, the composition of which is most simply expressed by the formula C5H8. From this result it was considered that lupulic acid is a derivative of an olefinic terpene. The author, furthermore, notes the points of distinction between a-lupulic acid (m. p. 54—56°), which was observed by Hayduck to be a constituent of the so-called a-resin, and is said to crystallise in small rhombohedra, and /3-lupulic acid (m. p. 92°), which has been described as forming long, glistening prisms. Both compounds were presumed to be unsaturated, to possess similar molecular weights, and to stand in some relationship to the essential oil of hops. Bamberger and Landsiedl (Zeitsch. ges. Brauw., 1902, 25, 461) describe the a-lupulic acid or hop-bitter acid as an amber-coloured, crystalline mass (m. p. 56°), which is readily soluble in nearly all solvents, and when oxidised by exposure to the air gives with ferric chloride a yellowish-brown coloration. They considered it to possess the formula C20H28O5 or C20H30O5. Lintner and Schnell (Zeitsch. ges. Brauw., 1904, 27, 666) were not successful in their attempts to obtain a-lupulic acid in a pure state, and they therefore examined the products formed from the acid by the action of an alcoholic solution of sodium hydroxide. They thus obtained, besides resinous matter and valeric acid, a crystalline substance (m. p. 92*5°), which was considered to possess the formula C]5H2404, and to be an unsaturated hydroxyketonic acid. They also proposed to designate the above-mentioned a-acid as “ humulon,” and its crystalline product of decomposition as “ humulin,” retaining for the so-called /3-acid the name “ lupulic acid/1](https://iiif.wellcomecollection.org/image/b30620387_0005.jp2/full/800%2C/0/default.jpg)
