Citrus Shows Promise for Certain Cancers, Other Diseases

By Kathleen Phillips

For more than 200 years, people have known that citrus consumption prevents scurvy. Since the 1930s, it’s been common knowledge that vitamin C was the curative cause.

Now Texas A&M University researchers in horticulture are teaming with those in biochemistry and biophysics to explore more citrus compounds and linking them to the prevention and possible cure of a variety of diseases from cancer to bone density and strength.

Among the promising studies is one that linked citrus compounds called limonoids to stopping the growth of neuroblastoma cells in lab tests. Neuroblastomas account for about 10 percent of all cancer in children, according to Dr. Ed Harris, Texas Agricultural Experiment Station biochemist. Researchers on that TAES-funded study now seek to learn the reasons for the stop-action behavior and, will eventually try the citrus concoction in humans.

“Limonoids are naturally occurring, nutrient-packed pigments that give color and taste to fruit,” says Harris, who collaborated on the study with Vegetable and Fruit Improvement Center director Dr. Bhimu Patil. “Unlike other anticancer drugs that are toxic, limonoids apparently do not hurt a person. That’s the beautiful potential.”

Shibu Poulose, Patil’s graduate student working in Harris’ lab, successfully isolated the limonoids.

“He was able to determine the preventive effects of limonoids on neuroblastoma in triggering the cells to commit suicide while having no toxic effects on the normal cells,” Patil says. Most remarkable was that the limonoids were effective at a level one would find in one or two glasses of orange juice.

Patil has built a career on citrus, which he describes as “a vast reservoir of anticarcinogens.” He believes that the potential for citrus reaches even farther. He leads a $1.1 million U.S. Department of Agriculture Initiative for Future Agriculture and Food Systems grant that draws on collaborators from the University of Texas System and Baylor School of Medicine to that end.

“Dr. Ed Miller, at the Baylor College of Dentistry in Dallas, found that several of these limonoids can inhibit the development of carcinogen-induced neoplasia in a model for oral cancer. Some of these biologically active limonoids are present in citrus fruits and juices at extremely high concentrations,” Patil says of one of the grant’s results.

Another collaborative study under the grant, in the labs of Dr. Nancy Turner at the University of Texas at Austin and Dr. Lupton at Texas A&M, showed that colon cancer is “highly responsive to diet” in different cultures, Patil says. That research judged the ability of whole grapefruit, irradiated grapefruit and two compounds isolated from grapefruit (naringin and limonin) to protect against early colon cancer lesions in rats, Patil says.

“Rats consuming all four of the experimental diets had fewer of the lesions that are thought to be predictive of eventual colon cancer development,” he says. And the findings are not limited to cancer research, Patil adds.

“Certain bioactive compounds such as hesperdin, limonin and naringin significantly impact bone strength and bone density in animal studies in Dr. Farzad Deyhim’s lab,” he says, citing studies at Texas A&M University–Kingsville.