Humulus. U. S.
"The carefully dried strobiles of admixture of Humulus Lupulus Linne (Fam. Moraceae) bearing their glandular trichomes and without the presence or more than 2 per cent. of stems, leaves or other foreign matter. Preserve it in tightly-closed containers, protected from light." U. S.
Lupulus, Br. Pharm. 1898; Hop; Strobili Humuli, s. Lupuli; Houblon, Fr. Cod.; Hopfen, G.: Luppolo, It.; Lupulo (Fruto de), Hombrecillo, Sp.
Hops, under the title "Lupulus" were deleted from the British Pharm. (1914).
The hop plant is a twining, rough perennial having angular, rough, flexible stems, which twine around neighboring objects in a spiral direction from left to right, and climb to a great height. The leaves are opposite, and stand upon long footstalks. The smaller are sometimes cordate; the larger have three or five lobes; all are serrate, of a deep green color on the upper surface, and, together with the petioles, extremely rough, with minute prickles. At the base of the footstalks are two to four smooth, ovate, reflexed stipules. The flowers are numerous, axillary, and furnished with bracts. The staminate flowers are a yellowish-white, and arranged in panicles; the pistillate, which grow on a separate plant, are pale green, and disposed in solitary, peduncled aments, composed of membranous scales, ovate, acute, and tubular at the base. Each scale bears, near its base, on its inner surface, two flowers, consisting of a roundish compressed ovary, and two styles, with long filiform stigmas. The aments are converted into ovate membranous cones or strobiles, the scales of which contain, each, at its base, two small achenes, surrounded by a yellow, granular powder or the so-called Lupulin. Only the pistillate plants are cultivated by the hop growers in Europe, and it is interesting to note that the unfertilized pistillate plants produce strobiles richer in aroma and more plenteous in lupulin. The plants flower in August and the fruits are harvested during September. The hops grown in this country contain a great many achenes, showing that the staminate plants are also cultivated. The strobiles are collected when the scales change from a light golden to a somewhat deeper hue.
The hop plant is a native of North America and Europe. In parts of New England, New York, and Michigan it is extensively cultivated, and most of the hops consumed in the United States is supplied by those districts. England probably produces the largest quantity of hops, with Germany and Austria next in order. The part of the plant used is the fruit or strobiles. These, when fully ripe, are picked, dried by artificial heat, packed in bales, and sent into the market under the name of hops.
By separating the volatile oils and determining its acid and ester value, Rabak (C. D., lxxxv, 376) is able to distinguish American grown from imported hops. He finds that the European hops always show a lower ester value in the volatile oil than do the American.
Hops consists of numerous thin, translucent, veined, leaf-like scales, which are of a pale greenish-yellow color, and contain near the base two small, round, black achenes. They are officially described as follows: "Strobile ovoid-cylindrical, about 3 cm. in length, consisting of a narrow, hairy, flexuous rachis and numerous, imbricated, yellowish-green to pale brown, obliquely-ovate, membranous scales, the base of each with numerous, yellowish-brown, glandular hairs, and frequently infolded on one side, enclosing a subglobular, light brown, very glandular achene; odor strong and characteristic, becoming disagreeable and valerian-like on aging; taste aromatic and bitter. Hops yield not more than 8 per cent. of ash." U. S.
Though brittle when quite dry, they are pulverized with great difficulty. Their odor is strong, peculiar and fragrant; their taste very bitter, aromatic, and slightly astringent. Their aroma, bitterness, and astringency are imparted to water by decoction, but the first mentioned property is dissipated by long boiling. The most active part of hops is a substance formed on the surface of the scales, and, in the dried fruit, existing in the state of very small granules. This substance was called lupulin by A. W. Ives of New York, by whom its properties were first investigated and made generally known, though it was previously noticed by Sir J. E. Smith of England, and Planche of France. The scales themselves, however.. are not destitute of virtues, and contain, as shown by Payen and Chevallier, the same active principles as does lupulin, though in less proportion.
Hops are often subjected in Germany to the fumes of burning sulphur, because of the supposition that they keep better when thus treated. Besides, by being partially bleached by the process, old hops, which have suffered from time, having become darker, generally spotted, and weaker, assume a brighter appearance, as if fresher, and generally command a better price in the market. To detect the consequent presence of sulphurous acid, the brewers put a silver spoon in a mixture of hops and water, under the impression that it will produce a black stain upon the silver. But this test will answer only when applied within a fortnight after the use of the sulphur. A more delicate method is that of Heidenreich, who puts twenty or thirty strobiles of the hops in a flask with zinc and hydrochloric acid, and passes the hydrogen evolved through solution of lead acetate. If sulphurous acid be present, hydrogen sulphide will be produced, which will occasion a dark precipitate with the solution. But even this plan often fails when the hops have been kept more than three or four weeks. A modification of this test has been proposed by R. Wagner. For the solution of lead acetate used in Heidenreich's method there is to be substituted a solution of sodium nitroprusside, so weak as to have a very light brown color, to which have been added a few drops of solution of potassium hydroxide. If the gas evolved contain the minutest proportion of sulphur, a violet color will be produced when the first bubble passes into the solution; and this will, by a continuance of the process become a magnificent purple. The least trace of sulphurous acid may thus be found, but a few months after the sulphuring of hops none at all can be detected.
Hops are said to be sometimes threshed in order to separate the lupulin, which is sold separately. Their efficiency is thus, no doubt, greatly impaired. Hops thus treated have the scales more or less broken; and any parcel presenting this appearance is to be suspected. Hops often contain a variable quantity of lupulin in consequence of the granules of this substance separating, especially on agitation, and seeking the lower portion of the mass, which thus becomes richer, while the upper is poorer. They should always be examined in reference to the lupulin they contain, and, if nearly or quite destitute of it, should be deemed of inferior value and not be used medicinally.
LUPULIN, N. F. IV.—Lupulin is obtained by rubbing or threshing and sifting the strobiles, of which it constitutes from one-sixth to one-tenth by weight. It is in the state of a yellowish powder, mixed with minute particles of the scales, from which it cannot be entirely freed when procured by a mechanical process. It has the peculiar flavor of hops, and appeared to Lebaillif and Raspail, when examined by the microscope, to consist of glandular hairs filled with a yellow matter. They originate in a cell formed among those of the epidermis, and, when fully developed, secreting a resinous matter. (J. P. C; 3e ser., xxvi.) It is inflammable, and when moderately heated becomes somewhat adhesive. The odor of lupulinic grains resides in the essential oil. This is obtained to the extent of 0.9 per cent. by distilling hops with water. When distilled from the fresh strobiles the oil has a greenish color, but a reddish brown when old hops have been employed. It is devoid of rotatory power, neutral to litmus paper, and gives no remarkable coloration with concentrated sulphuric acid. According to Chapman (J. Chem. S., 1895, 54, 780) the essential oil consists of two terpenes, one C10H16, and the other C10H16, boiling between 160° and 171° C. (320° and 339.8° F.) and a sesquiterpene called humulene, boiling at 263° to 266° C. (505.4°-510.8° F.). This latter makes up almost two-thirds of the oil. There is also a small amount of an oxygenated constituent, probably C10H18O. The bitter principle formerly called lupulin or lupulite was first isolated by Lermer, who called it the bitter acid of hops (Hopfenbittersäure). It crystallizes in large brittle rhombic prisms, and possesses the peculiar bitter taste of beer. Its composition is C32H50O7. Lupulin consists chiefly of wax (myricyl palmitate, according to Lermer) and resins, one of which is crystalline and unites with bases.
Besides the constituents of the glands, hops contain, according to Etti, lupulo-tannic acid and phlobaphene. The former is a whitish, amorphous mass, soluble in alcohol, hot water, or acetic ether, but not in ether. By heating the humulo-tannic acid to 130° C. (266* F.), or by boiling its aqueous or alcoholic solution, it gives off water and is transformed into phlobaphene, a dark-red amorphous substance,
2C25H24O13—H2O = C50H46O25
The latter substance, on boiling it with diluted adneral acids, becomes hydrolized, and furnishes glucose and hop-red, according to the reaction:
C50H46O25 + 2H2O = C38H26O15 + 2C6H12O6
From raw phlobaphene, ether removes the bitter principles of hops, a colorless crystallizable and a brown amorphous resin, besides chlorophyll and essential oil. (Pharmacographia, 2d ed.) The existence of a peculiar alkaloid in hops, suggested by Lermer in 1863, and confirmed by Griessmayer, has been denied. A. Chaston Chapman (P. J., 1912, xcii, 878), found cultivated hops to contain from 1.7 to 4 per cent. of nitrogen which is a constituent of the following principles recognized by him in an investigation of the subject: aspartic acid, 1-asparagine, choline, betaine, adenine, histidine, hypoxanthine, and arginine, besides an unidentified base, no trace of a morphine-like alkaloid could be detected, although this has been stated by some authorities to be present. Etti found arable (pectic) acid, phosphates, nitrates, malates, citrates, and also sulphates, chiefly of potassium, to occur in hops. The amount of ash afforded by hops dried at 100° C. (212° F.) would appear to be on an average about 6 to 7 per cent. (U. S. P. IX not more than 8 per cent.) H. Bungener has isolated from hops a bitter crystalline substance, C25H35O4, which is insoluble in water, but soluble in alcohol and alkaline solutions. He believes it to be identical with Lenner's hop-bitter acid, to be feebly acid, and to possess the character of an aldehyde. (P. J., 1884.)
Uses.—Hops are an aromatic bitter and hence may be useful in atonic dyspepsia. By many they are believed to have a sedative effect on the nervous system and are used in hysteria, restlessness, insomnia, and the like. Whether this latter action is due to anything more than an effect through the imagination is open to question.
An infusion prepared with half an ounce of hops and a pint of boiling water may be given in the dose of four fluidounces (120 mils). The tincture was a British official preparation of hops, but the alcohol probably acts more decidedly upon the system than the hops. The fluidextract of hops of the N. F. IV is superior because of the relatively smaller amount of alcohol. A pillow of hops has proved useful in allaying restlessness and producing sleep in nervous disorders. They should be moistened with water containing a trace of glycerin previously to being placed under the head of the patient, in order to prevent rustling. Fomentations with hops, and cataplasms made by mixing them with some emollient substance, are often beneficial in local pains and tumefactions.
The effects of hops may be obtained conveniently by the use of lupulin, which, although at one time much employed as an anaphrodisiac, has fallen into deserved desuetude.
Dose, thirty to ninety grains (2.0-5.8 Gm.).
Off. Prep.—Elixir Humuli (from Fluidextract), N. F.; Fluidextractum Humuli, N. F.; Tinctura Humuli, N. F.
The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.