Abstract:

Biological oxidation is an energy-producing reaction in the metabolism of living organisms. Under cellular metabolism or extracellular stress, the skin cells continuously produce highly active free radicals and reactive oxygen species. Over-producing these highly active molecules causes cell structure changes, leading to early apoptosis and skin problems. Antioxidants help to improve the antioxidant capacity of the organisms and eliminate the harmful effects of free radicals and reactive oxygen species. Herein, free radicals and reactive oxygen species, oxidative stress, oxidative damage and the skin diseases caused by them, as well as the mechanisms of antioxidant action, have been reviewed. The plant extracts with antioxidant activity have been mainly introduced, including phenols, phenolic acids, flavonoids, stilbenes, procyanidin, carotenoids and vitamins. Among them, phenolic compounds are most important. Most polyphenols exist in conjugated forms and exhibit excellent antioxidant activity. The common structural feature of these natural antioxidants is the presence of phenolic hydroxyl groups or conjugated double bonds. For an antioxidant, the better the antioxidant effect it has, the easier it is to be reduced. The hydroxytyrosol, which is both water- and fat-soluble, has strong antioxidant capacity. The fat-soluble astaxanthin and water-soluble vitamin C also show good antioxidant activity. The antioxidation mechanisms of some plant ingredients have been described to provide reference for the application of plant extracts as antioxidants in cosmetics.

Key words: plant extract, antioxidant, free radical, reactive oxygen species, cosmetics