Camellia Sinensis (Green Tea) Epigallocatechin Gallate.
Of the many valuable chemicals present in green tea, polyphenols and catechins (epigallocatechin gallate - EGCG) in particular, are really good for us and our skin. Scientific research illustrates EGCG to be effective as an antioxidant, in repair of damage done by UVA radiation, antitumor (benign and malignant), and in prevention of damaging mutations.* Another benefit of EGCG is for blemish control, helping to keep pores open by controlling sebum secretion.*
Polyphenols in general are not brown or beige, but they turn brown upon oxidation (like when potatoes and apples are cut and exposed to air). This non-enzymatic process, called browning, makes life difficult for the biochemist. I did research in photosynthesis for many years, and we almost always used young spinach leaves because they contain very few polyphenols, which make it difficult to isolate intact chloroplasts when oxidized.*
(*See reference tab for scientific resources)
Fujiki, Hirota; Suganuma, Masami; Okabe, Sachiko; Sueoka, Eisaburo; Suga, Kenji; Imai, Kazue; Nakachi, Kei; Kimura, Shunsaku (1999) Mechanistic findings of green tea as cancer preventive for humans. Proceedings of the Society for Experimental Biology and Medicine: 220(4), 225-228.
Huang, Chieh-Chen; Fang, Jai-You; Wu, Wen-Bin; Chiang, Han-Sun; Wei, Yuan-Ju; Hung, Chi-Feng (2005) Protective effects of (-)-epicatechin-3-gallate on UVA-induced damage in HaCaT keratinocytes. Archives of Dermatological Research: 296(10), 473-481.
Hsu, S.; Yamamoto, T.; Borke, J.; Walsh, D. S.; Singh, Baldev; R., Sushma; T., Kamatani; Nah-Do, N.; Lapp, C.; Lapp, D.; Foster, E.; Bollag, W.B.; Lewis, J.; Wataha, J.; Osaki, T.; Schuster, G. (2005) Green tea polyphenol-induced epidermal keratinocyte differentiation is associated with coordinated expression of p57/KIP2 and caspase 14. Journal of Pharmacology and Experimental Therapeutics: 312(3), 884-890.
Lu, Yao-Ping; Lou, You-Rong; Xie, Jian-Guo; Peng, Qing-Yun; Liao, Jie; Yang, Chung S.; Huang, Mou-Tuan; Conney, Allan H. (2002) Topical applications of caffeine or (-)-epigallocatechin gallate (EGCG) inhibit carcinogenesis and selectively increase apoptosis in UVB-induced skin tumors in mice. Proceedings of the National Academy of Sciences USA: 99(19), 12455-12460.