The constituents of hops / Frederick B. Power, Frank Tutin and Harold Rogerson.

  • Frederick Belding Power
Date:
[1913?]
Catalogue details

Licence: Public Domain Mark

Credit: The constituents of hops / Frederick B. Power, Frank Tutin and Harold Rogerson. Source: Wellcome Collection.

    6/30 page 1270
    Siller (Zeitsch. Nahr. Genussm., 1909, 18, 241), with consideration of the investigation of Hayduck (loc. cit.), has proposed a method for quantitatively determining the a-, and y-resins of the last- mentioned author, and also the so-called a-hop-bitter acid. Since the latter substance was obtained from the lead compound of the mixed resins by decomposing it with sulphuric acid, it must have consisted to a large extent of ordinary fatty acids, which the present authors have shown to be contained in considerable amount in hops. Adler (Zeitsch. ges. Brauw., 1912, 35, 406) and Seibriger (Woch. Brau., 1913, 30, 177, 196) have suggested methods for determining the bitter substances of hops by extracting the latter with light petroleum or carbon tetrachloride, and titrating the resulting extract with alcoholic potassium hydroxide. Such methods, how¬ ever, are entirely empirical, and, as in the case of the method proposed by Siller (loc. cit.), the substances actually determined would no doubt consist chiefly of fatty acids. Griessmayer (Dingier’s 'polyt. J., 1874, 212, 67) distilled a decoction of hops with an alkali hydroxide, and obtained, besides ammonia and trimethylamine, a small amount of a liquid which was said to have an odour resembling that of coniine. This very indefinite substance was presumed to be a volatile alkaloid, for which the name “ lupuline ” was proposed, but no crystalline salt could be prepared from it, nor does the presence of nitrogen appear to have been determined. Griess and Harrow (Ber., 1885, 18, 717) showed that hops contain a very small proportion (not more than 0‘02 per cent.) of choline. As a very dilute solution of choline was found to dissolve relatively large amounts of hop-resin, whereby an intensely bitter taste was imparted to the liquid, they thought it not unlikely that such a combination occurs in the hops, thus forming the bitter substance which is soluble in water. The preceding survey of the very voluminous literature pertaining to the chemistry of hops, although by no means complete, will afford an indication of the present state of knowledge on the subject. In view of the existing confusion, it has been considered that other and more systematic methods of examination than those hitherto employed might serve more clearly to define the character of the constituents of this important natural product, and thus explain the numerous discrepancies of statement. The results of the present investigation, with the deductions ^'om them, are summarised at the end of this paper.
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