This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Hops are the fruit or strobiles of Humulus Lupulus, a climbing perennial plant, growing wild in Europe and North America, and largely cultivated in both continents. The fruit is picked when ripe, dried by artificial heat, packed in bales, and thus sent into market.
Sensible Properties. Each strobile has the shape of a cone flattened by pressure, and consists of a number of thin, translucent, leaf-like scales, one overlapping another, of a pale yellowish-green colour, with two small black seeds near the base of each, and minute yellowish granules upon their surface, easily separable when the fruit is quite dry. Hops are of difficult pulverization, of a strong, peculiar, narcotic, yet fragrant odour, and of an extremely bitter, aromatic, somewhat astringent taste. They impart their sensible and medicinal properties to alcohol and water.
Active Constituents. The virtues of hops depend probably, in chief, upon a peculiar bitter principle called lupulite or lupuline, but to which the name of humulin would be more appropriate, as more distinct from lupulin, which had been introduced into use, with another meaning, before the discovery of the principle referred to. They contain also a volatile oil, which is the source of their aroma, and a small proportion of tannic acid. According to Mr. W. Jauncey, the oil is formed in the hops during desiccation, as he has failed to discover it in fresh strobiles. (Edin. Med. Journ., iii. (699.) Their other constituents have no special interest for the physician.
The active principles of hops are diffused, in some degree, throughout their whole substance, but are mainly concentrated in the yellowish granules upon the surface of the scales. These granules are separated for use, and constitute a distinct medicine, recognized in our Pharmacopoeia by the name of lupulin, proposed for it by the late Dr. A. W. Ives, of New York, who first brought it into notice.
Lupulin (Lupulina, U.S.) is prepared by rubbing or threshing the hops, and then sifting the coarse powder obtained. It consists of yellowish granules, almost always interspersed with minute fragments of the scales themselves, from which it is impossible entirely to separate them, as ordinarily procured. Lupulin has the odour and taste of hops, and contains the volatile oil and bitter principle above mentioned, with mere traces of the tannic acid. As it possesses all the virtues of hops, in a more concentrated and convenient form, it is generally preferred for internal use.