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Molecules 2016, 21(10), 1345; doi:10.3390/molecules21101345

Ultraviolet B (UVB) Photosensitivities of Tea Catechins and the Relevant Chemical Conversions

Tea Research Institute, Zhejiang University, Hangzhou 310058, China
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Author to whom correspondence should be addressed.
Academic Editors: Declan P. Naughton and Derek J. McPhee
Received: 13 August 2016 / Revised: 22 September 2016 / Accepted: 6 October 2016 / Published: 10 October 2016
(This article belongs to the Special Issue Polyphenols and Antioxidants–The Chemistry of Tea)
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Abstract

Ultraviolet B (UVB) photosensitivities of eight catechins were screened. In both water and ethanol, epicatechin (EC, 575 μM) and catechin (C, 575 μM) exhibited low photostabilities under 6 h UVB radiation with the generation of yellow photoproducts, while other catechins (epigallocatechin gallate, epigallocatechin, epicatechin gallate, gallocatechingallate, gallocatechin, catechin gallate) were relatively UVB-insensitive. Photoisomerization and photolysis were two important UVB-induced reactions to EC whereas photolysis was the dominant reaction for C. The influencing factors of time (2–10 h), solvent (water, ethanol) and substrate concentration (71.875–1150 μM) on UVB-induced chemical conversions of EC and C were investigated, and eight photoproducts were identified through ultra performance liquid chromatography-diode array detection-tandem mass spectrometry (UPLC-DAD-MS/MS) and 1H nuclear magnetic resonance (1H-NMR analysis). Photolysis reaction involved two pathways, including radical reaction and photo-induced electron transfer reaction. The 2,2-diphenylpicrylhydrazyl (DPPH) scavenging abilities of eight catechins did not change upon 6 h UVB irradiation. EC and C are photosensitive catechins among eight catechins causing deep color. View Full-Text
Keywords: photostability; catechins; photoisomerization; photolysis; photoproducts photostability; catechins; photoisomerization; photolysis; photoproducts
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Shi, M.; Nie, Y.; Zheng, X.-Q.; Lu, J.-L.; Liang, Y.-R.; Ye, J.-H. Ultraviolet B (UVB) Photosensitivities of Tea Catechins and the Relevant Chemical Conversions. Molecules 2016, 21, 1345.

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