Beta-carotene as an interceptor of free radicals.

Kinetics of nonenzymic and nonphotochemical oxidation of beta-carotene have been studied. The rate constants for the reactions of beta-carotene with initiator-derived C-centered and peroxyl radicals in solution were measured as approximately 10(4) and 5 x 10(5) - 1 x 10(4) M-1s-1, respectively. beta-Carotene-derived free radicals have been shown to be less reactive toward polyene than initiator-derived radicals. This suggests that beta-carotene might behave as an interceptor of free radical species regardless of the oxygen pressure in the environment. The mechanism for beta-carotene oxidation covering the main pathways for formation, transformation, and decay of free radicals has been formulated. In combination with experimental kinetic parameters and their temperature correlation, computer modeling has been used to solve the reaction kinetics numerically. The model proposed enables analysis of the kinetics of beta-carotene consumption and oxygen uptake under various conditions, as well as the influence of beta-carotene on oxidation of polyunsaturated fatty acids and their esters.