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Possible Cancer-Fighting Properties Found in Certain Bioflavonoids

By Jesús García
August 9, 2000

Orange and other citrus juices contain compounds that may help the body fight off cancer-causing substances, Agricultural Research Service scientists report.

The citrus compounds, called bioflavonoids, not only give citrus juice its flavor and color but are potent antioxidants, according to ARS scientists Hamed Doostdar and Richard Mayer. They’re with the U.S. Horticultural Research Laboratory in Ft. Pierce, Fla.

The scientists have identified several bioflavonoids from citrus that inhibit certain cytochrome P450 enzymes. Thwarting these enzymes is important, because some of them can turn cigarette smoke, pesticides and other substances into carcinogens. Cigarette smoke and pesticides are called procarcinogens--meaning they may not cause cancer in their original form but could become carcinogenic later inside the body.

One P450 enzyme, known as P450 1B1, turns procarcinogens into carcinogens. It is also present at high levels in breast and prostate cancer cells, and can even modify the female hormone estradiol into a possible carcinogen.

The ARS scientists have found that hesperetin, the most abundant bioflavonoid in orange juice, inhibits the P450 1B1 enzyme from metabolizing procarcinogens, reducing the chances that the body could turn these substances into carcinogens.

Hesperetin’s effect on enzyme P450 1B1 might lead to the development of alternatives to traditional cancer chemotherapy treatments that affect healthy as well as diseased cells. Only cells containing the enzyme P450 1B1, which are largely cancer cells, would be affected by hesperetin.

ARS is the U.S. Department of Agriculture’s principal scientific research agency.

Scientific contact: Richard Mayer, U.S. Horticultural Research Laboratory, Ft. Pierce, Fla., phone (561) 462-5897, fax (561) 462-5800,