Prooxidant Behavior

The ability to quench singlet oxygen, porphyrin triplet energies, and free radical reactions are examples of the antioxidant nature of carotenoids. An in vitro study showed that, at low partial pressures of oxygen (pO2), ¡-carotene consumed peroxy radicals efficiently as in: CARL + ROO-! CAR/+ + ROO. At higher pO2, however, ¡-carotene became a prooxi-dant through autooxidation. Recently, experiments in intact murine normal and tumor thymocytes showed that ¡-carotene lost its antioxidant potency at higher pO2, and the effect was more pronounced in tumor cells. It is still unclear, however, whether some effects of carotenoid behavior at higher pO2 are due to prooxidant activity or simply lack of antioxi-dant ability. Prooxidant effects of ¡-carotene have also been used to explain results from intervention trials of ¡-carotene supplementation in diets of smokers or individuals suffering from asbestosis where the incidence of carcinogenesis was higher in those individuals taking the ¡-carotene supplement. Generation of deleterious oxidation products from ¡-carotene reaction with reactive oxygen species in tobacco smoke or as a result of asbestosis has been proposed. Interference with retinoid signaling was also considered. However, whether those effects were due to prooxidant behavior or lack of antioxi-dant ability is still unclear.

Your Heart and Nutrition

Your Heart and Nutrition

Prevention is better than a cure. Learn how to cherish your heart by taking the necessary means to keep it pumping healthily and steadily through your life.

Get My Free Ebook

Post a comment