Oh

Epicatechin

HC=CHCOOH

OCHg essential (eg, phenolic acids and isoflavones) and essential (a-tocopherol) phenolics inhibit oxidation by acting as chain-breaking antioxidants that are capable of inactivating free radicals and thus stopping the autocatalytic free-radical reaction (5). Phenolic compounds are efficient chain-breaking antioxidants because they are capable of scavenging free radicals, resulting in the formation of low-energy phenolic radicals that in turn do not have sufficient energy to further promote oxidative reactions. Ascorbic acid can also act as a chain-breaking antioxidant; however, it can also promote the reduction of transition metals (5). This metal-reducing activity will increase the pro-oxidant activity of metals because their reduced states rapidly promote the decomposition of peroxides into free-radical species.

Carotenoids can act as chain-breaking antioxidants when oxygen concentrations are low. However, in the presence of high oxygen concentrations, carotenoid radicals can actually increase oxidative reactions (6,7). Carotenoids are most effective at inhibiting oxidative reactions in the pres ence of systems that produce the reactive oxygen species, singlet oxygen. Singlet oxygen is produced from atmospheric oxygen when compounds known as photosensitiz-ers (eg, chlorophyll, riboflavin, and myoglobin) are energized by light to an excited state. The excited state of the photosensitizer can then transfer its energy to oxygen to produce singlet oxygen that in turn oxidizes unsaturated fatty acids and amino acids (8). Carotenoids inhibit this reaction by physically absorbing energy from the excited photosensitizer or from singlet oxygen and then slowly returning the energy to the surrounding media through vibrational and rotational interactions. In order for a carotenoid to be able to inactivate singlet oxygen and activated photosensitizers through physical quenching, it must contain at least nine double bonds (9).

Sleeping Sanctuary

Sleeping Sanctuary

Salvation For The Sleep Deprived The Ultimate Guide To Sleeping, Napping, Resting And  Restoring Your Energy. Of the many things that we do just instinctively and do not give much  of a thought to, sleep is probably the most prominent one. Most of us sleep only because we have to. We sleep because we cannot stay awake all 24 hours in the day.

Get My Free Ebook


Post a comment