Researchers at Oregon State University first discovered the cancer-related properties of this flavonoid compound called xanthohumol about 10 years ago. A recent publication by an OSU researcher in the journal Phytochemistry outlines the range of findings made since then. And many other scientists in programs around the world are also beginning to look at the value of these hops flavonoids for everything from preventing prostate or colon cancer to hormone replacement therapy for women.
"Xanthohumol is one of the more significant compounds for cancer chemoprevention that we have studied," said Fred Stevens, a researcher with OSU's Linus Pauling Institute and an assistant professor of medicinal chemistry in the College of Pharmacy. "The published literature and research on its properties are just exploding at this point, and there's a great deal of interest."
Quite a bit is now known about the biological mechanism of action of this compound and the ways it may help prevent cancer or have other metabolic value. But even before most of those studies have been completed, efforts are under way to isolate and market it as a food supplement. A "health beer" with enhanced levels of the compound is already being developed.
"We can't say that drinking beer will help prevent cancer," Stevens said. "Most beer has low levels of this compound, and its absorption in the body is also limited. But if ways can be developed to significantly increase the levels of xanthohumol or use it as a nutritional supplement - that might be different. It clearly has some interesting cancer chemopreventive properties, and the only way people are getting any of it right now is through beer consumption."
Xanthohumol was actually first discovered in 1913, isolated as a yellow substance found in hop s. Researchers started studying its molecular structure in the 1950s, but for decades the only people who showed any real interest in it were brewers, who were trying to learn more about how hops help impart flavor to beer.
In the 1990s, researchers at OSU, including Stevens and toxicologist Don Buhler, began to look at the compound from another perspective - its anti-cancer properties. It showed toxicity to human breast, colon and ovarian cancer cells, and most recently has shown some activity against prostate cancer in OSU studies.
Xanthohumol appears to have several mechanisms of action that relate to its cancer preventive properties, scientists say. It, and other related flavonoid compounds found in hops, inhibit a family of enzymes, commonly called cytochromes P450 that can activate the cancer process. It also induces activity in a "quinone reductase" process that helps the body detoxify carcinogens. And it inhibits tumor growth at an early stage.
In recent years, it has also been shown that some prenylflavonoids found in hops are potent phytoestrogens, and could ultimately have value in prevention or treatment of post-menopausal "hot flashes" and osteoporosis - but no proper clinical trials have been done to study this.
Information about these compounds appears to be spreading. Hop-containing herbal preparations are already being marketed for breast enlargement in women, the OSU research report said, without waiting for tests to verify their safety or efficacy. And a supposed "health" beer is being developed in Germany with higher levels of xanthohumol.
It's possible, scientists say, that hops might be produced or genetically engineered to have higher levels of xanthohumol, specifically to take advantage of its anti-cancer properties. Some beers already have higher levels of these compounds than others. The lager and pilsner beers commonly sold in domestic U.S. brews have fairly low levels of these compounds, but some po rter, stout and ale brews have much higher levels.
Ideally, researchers say, cancer chemoprevention is targeted at the early stages of cancer development and prevented by long-term exposure to non-toxic nutrients, food supplements or drugs that prevent the formation of cancers. With its broad spectrum activity, presence in food products, and ability to inhibit cancer at low concentrations, xanthohumol might be a good candidate for that list, experts say.
Xanthohumol also appears to have a role as a fairly powerful antioxidant - even more than vitamin E. And it has shown the ability to reduce the oxidation of LDL, or bad cholesterol.