Photostability of Epigallocatechin-3-Gallate in topical formulations – Effect of sunscreens and antioxidant agents
The major and most active catechin of green tea, (_)-epigallocatechin-3-gallate has been shown, in animal and human skin, to prevent the harmful effects induced by exposure to the solar UV radiation. Although the chemical stability of EGCG ((−)-Epigallocatechin-3-gallate) has been extensively studied, its photochemical behaviour has not been investigated. In order to assure the cutaneous photo-protective effectiveness of EGCG, it is important to examine its stability under sunlight. The present study reports on the systematic evaluation of the photo-degradation of EGCG and of the use of UV filters and antioxidants as stabilzers.
In recent years, green tea has received considerable attention because of epidemiological studies showing that its consumption is associated with a reduced risk of cardiovascular and neurodegenerative diseases and certain cancers (1–3). Moreover, the extract of green tea (Fig 1) has gained great interest for the prevention of the harmful effects (photodermatoses, cutaneous photoageing, immunosuppression and various forms of skin cancers) induced in human skin by exposure to the solar UV radiation (4–6). This protective activity has been ascribed mainly to the polyphenolic
flavonoid constituents, known as catechins, present in high amount in green tea (4,6,7). These compounds are powerful
antioxidants exhibiting several pharmacological properties exerted through different mechanisms (5–8).
(−)-Epigallocatechin-3-gallate (EGCG; Figure 2), the most abundant and biologically active catechin of green tea
(5,8–10) has been shown, in animal and human skin, to prevent, in vitro and in vivo, oxidative injuries (proteins and lipid
oxidation, DNA single strand breaks) and depletion of antioxidant enzym ...