Naturally occurring substances in citrus juices, called flavanoids, show promise against prostate cancer, lung cancer and melanoma in laboratory studies, according to a joint Canadian-United States study. Twenty-two flavonoids were examined during the study; this is the first time they have been tested against melanoma and prostate and lung cancer.

Of the 22 flavanoids studied, two that occur naturally in tangerine juice - tangeretin and nobiletin -were the most effective inhibitors of human prostate cancer cells. 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. In comparison with other compounds the researchers have studied, the tangerine and orange flavonoids are very effective. Small amounts inhibit proliferation of cancer cells.

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.

219th National Meeting of the American Chemical Society San Diego March 19, 2000