Chemistry of carotenoid oxidation and free radical reactions

When oxygenic photosynthesis evolved, one of the key functions of carotenoids was to protect aerobic photosynthetic organisms against destruction by photodynamic sensitization. Aerobic photosynthesis would not exist without the coevolution of carotenoids alongside the chlorophylls. As carotenoids are abundant in nature, in many fruits and vegetables, they are able to react with excited states of appropriate energy and quench them, and they can react with free radicals according to their reactivity, redox potentials, and X-H bond energies. This report concerns the bimolecular reactions of carotenoids with oxygen species, such as O-3(2), O-1(2) HO., HOO., O-2(.-), etc.