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Natural Substances In Orange, Tangerine Inhibit Cancer

Effective Against Prostate Cancer, Lung Cancer and Melanoma

 

 

SAN FRANCISCO, March 30 — Naturally occurring substances in

citrus

juices, called flavonoids, show promise against prostate cancer, lung

cancer and melanoma in laboratory studies, according to a joint

Canadian-United States study. The findings were presented here today

at the 219th national meeting of the American Chemical Society, the

world's largest scientific society. The weeklong meeting is

expected

to draw nearly 20,000 attendees from around the world.

 

Twenty-two flavonoids were examined during the study; this is the

first time they have been tested against melanoma and prostate and

lung cancer, says one of the lead researchers, Najla Guthrie, Ph.D.,

president of KGK Synergize, Inc., a research and development company

in London, Ontario, Canada. The research was conducted in

collaboration with the U.S. Department of Agriculture (USDA).

 

Orange and tangerine juice, in particular, produced " very

encouraging

results, " according to Guthrie.

 

Of the 22 flavonoids studied, two that occur naturally in tangerine

juice — tangeretin and nobiletin — " were the most effective

inhibitors

of human prostate cancer cells, " according to Guthrie and

colleague

John Manthey, Ph.D., of the USDA's Agricultural Research Station

in

Winter Haven, Fla. The compounds also inhibited the growth of

melanoma cells, notes Guthrie. Her lab previously reported that the

tangerine compounds were effective against breast cancer cells.

 

A flavonoid found in both tangerines and oranges, 5-desmethyl

sinensetin, inhibited human lung cancer cells most effectively,

according to Guthrie.

 

In comparison with other compounds the researchers have studied, the

tangerine and orange flavonoids are " very effective. " Small

amounts

inhibit proliferation of cancer cells, according to Guthrie.

 

A synthetic flavonoid, quercetrin tetramethyl ether, also inhibited

the growth of colon cancer cells during the studies, says Guthrie.

The synthetic flavonoid was made by modifying quercetrin extracts.

Quercetrin is found in many plants other than citrus, notes Guthrie.

 

" We looked at 22 flavonoids — some naturally occurring, some

synthetic — and these are the most effective out of them, "

Guthrie

points out. Some of the citrus compounds being studied are inhibiting

the cells in the same concentration range as the breast cancer drug

tamoxifen, she adds.

 

" The next step is to look at them in animals. " Among the

questions

still to be answered, she said, are: " How are they metabolized?

Do

they get to the cells? Do they have the same effect? "

 

Animal studies have begun, says Guthrie, but it is too early to

report preliminary data. She expects some results within about a

year.

 

Dr. Guthrie is President, KGK Synergize, Inc. in London, Ontario,

Canada.

 

Dr. Manthey is Research Chemist, U.S. Citrus and Subtropical Products

Research Laboratory, U.S. Department of Agriculture, Agricultural

Research Service, Winter Haven, Fla.