Inhibition of Oral Carcinogenesis by Citrus Flavonoids

Abstract

Six citrus flavonoids were tested for antineoplastic activity. The hamster cheek pouch model was utilized, and the solutions of the flavonoids (2.0–2.5%) and the solution of the carcinogen, 7,12-dimethylbenz[a]anthracene (0.5%), were applied topically to the pouches. The pouches of the positive controls were treated with the solvent used to dissolve the flavonoids and the solution of the carcinogen. The data show that 4 flavonoids (hesperetin, neohesperidin, tangeretin, and nobiletin) were inactive. The results with naringin and naringenin show that both of these flavonoids significantly lowered tumor number [5.00 (control group), 2.53 (naringin group), and 3.25 (naringenin group)]. Naringin also significantly reduced tumor burden [269 mm^m3(control group) and 77.1 mm^m3(naringin group)]. The data suggest that naringin and naringenin, 2 flavonoids found in high concentrations in grapefruit, may be able to inhibit the development of cancer.

ACKNOWLEDGMENTS

The authors gratefully acknowledge the technical assistance of Janice M. Lalor and Josephine E. Taylor. The tangeretin and nobiletin used in this study were a generous gift from Dr Wilbur W. Widmer at the Florida Department of Citrus in Lake Alfred, Florida. This study was supported by the Texas Advanced Technology Program under Grant No. 003658–0359–2001 and in part by a grant from the Florida Citrus Commission (DOC Contract No. 96027). An Advanced Technology Program supplemental grant for high school teachers awarded through the State of Texas funded Janice M. Lalor's salary.

Notes

^aGroup 1 was the control group, the group that was treated with the solvent used to dissolve the flavonoids. Group 2 was treated with the 2% solutions of tangeretin, and Group 3 was treated with the 2% solutions of nobiletin.

^bValues are means ± SE.

^aGroup 1 was the control group, the group that was treated with the solvent used to dissolve the flavonoids. Groups 2 through 5 were treated with the 2.5% solution of hesperetin (Group 2), the 2.5% solution of neohesperidin (Group 3), the 2.5% solution of naringenin (Group 4), or the 2.5% solution of naringin (Group 5).

^bValues are means ± SE.

^cP < 0.05 when these values are compared to the corresponding values for the control group (Group 1).