A compound found only in hops and the main product they
are used in - beer - has rapidly gained interest as a
micronutrient that might help prevent many types of cancer.
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 hops. 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 porter, 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.
About the Linus Pauling Institute: The Linus Pauling
Institute at OSU is a world leader in the study of micronutrients
and their role in promoting optimum health or preventing
and treating disease. Major areas of research include
heart disease, cancer, aging and neurodegenerative disease.
- More articles
on Anti-cancer properties
Reference
Source 131
November
18, 2005
