Initial efforts will focus on the isolation, purification and identification of active compounds, followed by toxicological studies and biochemical investigations into their mode of action.

Hops growers in the United States produced a crop of nearly 75 million pounds in 1994, comprising about 28% of world output and, according to a USDA summary, both acreage and production increased 50 percent between 1985 and 1994.  While the majority of that was dedicated to the brewing industry, hop extracts are used as flavorings in various non-alcoholic beverages,  candy, baked goods, gelatins, and puddings. Extracts and oil are also used in skin creams and lotions, for alleged skin-softening and skin-whitening properties.

Bitter, resinous substances produced in the glandular hairs of the strobiles ("cones") are used by brewers for the aroma and flavor that they impart to beer, and have for centuries been used as well for the bacteriostatic action and preservative qualities that they provide.  It was stated that hops were originally used in beer only for their preservative value, and that only later did beer drinkers acquire a taste for its delectable bitterness.   In a large portion of the world, beer is still safer for consumption than water.  Beginning or infrequent drinkers tend to enjoy lighter, less bitter beers while "seasoned drinkers" are more likely to prefer a hoppier beer.

Hops have been used in medicine as a bitter tonic and stomachic,  and as a calmative and sedative-hypnotic.  While the potency of any action that hops products have on the central nervous system in humans remains questionable,  many research papers over the last few years have affirmed this plant's pharmacological promiscuity.

Definition

Hops is the female inflorescence of Humulus lupulus L., a plant in the Cannabaceae, or hemp family.  An enormous array of varieties and cultivars have been developed over the centuries.  From a pharmaceutical standpoint, however, the definition of hops is somewhat more complex.  Several "phytomedicinal" preparations containing hops are offered for sale in pharmacies in Germany.  The hops included in these products are typically standardized based on TLC (thin-layer chromatographic) or HPLC (high-pressure liquid chromatographic) comparison of the material in question with authentic standards.  Currently, standardization is typically based on the "marker" compounds humulone, lupulone and xanthohumol.  While these compounds have been reported to show some biological activity, it is quite possible that other constituents may be more pharmacologically relevant.  A challenge to be overcome in the future is to identify active chemical components so that chemical standardization based on constituents that posess relevant biological activity (if any) may be achieved.

As is the case with all plant-based drugs, hops cannot be defined as concisely as can pure pharmaceutical compounds.  One of the primary phytochemical objectives of  hops research being conducted at the Center is to completely characterize, both chemically and biologically, a hops extract for subsequent biological, and ultimately clinical, evaluation.

There are three general classes of compounds at work:

The volatile oil contains chiefly the monoterpene myrcene, but also present is a vast array of mono- and sesquiterpenes that exist at various levels of oxidation, and as a group have been shown to possess a broad spectrum of antimicrobial activity.  Hops essential oils are used in perfumes, cereal beverages and tobacco. After storage for some time, the volatile oil may also contain degradation products from the bitter acids.

The "bitter acids" are resinous alicyclic phenolic acids and are subdivided into two groups, the a-acids and the b-acids.  The b-acids differ structurally from the a-acids by having one more prenyl (isopentenyl) group.  Both groups of bitter acids have in recent years been shown active in many different assays related to the treatment and/or prevention of cancer.

The flavonoids are the most recent group of hops compounds to receive attention.  Recent papers suggest that certain prenylated flavonoids present in hops could be responsible for the putative estrogenic activity of the plant, the existence of which has been debated for decades.

Pharmaceutical drug development typically begins with a pure, chemically defined substance, followed by in vitro assays, in vivo / animal studies, then a series of human clinical studies.  The basic definition of "hops" from a  pharmaceutical perspective is still open to interpretation, while an enormous body of literature including in vitro, in vivo, clinical, ethnomedical information is already available.  While it poses a challenge to pharmacognosists to sort out all of the [sometimes contradictory] information available, it is also somewhat of a unique advantage in the field of drug discovery and development to have such an enormous body of literature regarding the substance's biological activity.  We can determine from the outset that the substance is probably not very toxic (if it were, it would likely have been determined to be so in one of the numerous animal studies that have been conducted over the last several decades, and/or its use would presumably have been discontinued long ago).  We also have some idea from the literature as to the potential therapeutic use of  the substance in question. With regards to hops, two particular areas of interest will be investigated.  The report that the hop constituent 8-prenylnaringenin has potent estrogenic activity, and also the recent rise in popularity of "phytoestrogens" in the management of the climacteric and other hormone-related symptoms leads us to investigate the potential of Humulus as a phytoestrogen.  The fact that ethnomedical references to the sedative-hypnotic properites of hops are quite abundant and are supported to some degree by animal studies leads us to investigate the potential interaction between hops and the central nervous system