title: Ultraviolet B (UVB) Photosensitivities of Tea Catechins and the Relevant Chemical Conversions.
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.
authors.affiliation: Tea Research Institute, Zhejiang University, Hangzhou 310058, China. 21316161@zju.edu.cn.
authors.forename: Meng
authors.initials: M
authors.lastname: Shi
authors.affiliation: Tea Research Institute, Zhejiang University, Hangzhou 310058, China. 21416073@zju.edu.cn.
authors.forename: Ying
authors.initials: Y
authors.lastname: Nie
authors.affiliation: Tea Research Institute, Zhejiang University, Hangzhou 310058, China. xqzheng@zju.edu.cn.
authors.forename: Xin-Qiang
authors.initials: XQ
authors.lastname: Zheng
authors.affiliation: Tea Research Institute, Zhejiang University, Hangzhou 310058, China. jllu@zju.edu.cn.
authors.forename: Jian-Liang
authors.initials: JL
authors.lastname: Lu
authors.affiliation: Tea Research Institute, Zhejiang University, Hangzhou 310058, China. yrliang@zju.edu.cn.
authors.forename: Yue-Rong
authors.initials: YR
authors.lastname: Liang
authors.affiliation: Tea Research Institute, Zhejiang University, Hangzhou 310058, China. jx0515@163.com.
authors.forename: Jian-Hui
authors.initials: JH
authors.lastname: Ye
mesh_terms: D002392:Catechin / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D055668:Photochemical Processes; D010777:Photochemistry; D053719:Tandem Mass Spectrometry; D013662:Tea / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D013662:Tea; D002392:Catechin
keywords: catechins; photoisomerization; photolysis; photoproducts; photostability