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AuthorZhu, Yingdong
AuthorZhao, Yantao
AuthorWang, Pei
AuthorAhmedna, Mohamed
AuthorHo, Chi-Tang
AuthorSang, Shengmin
Available date2017-02-23T07:30:27Z
Publication Date2015-01
Publication NameChemical Research in Toxicologyen_US
CitationTea Flavanols Block Advanced Glycation of Lens Crystallins Induced by Dehydroascorbic Acid Yingdong Zhu, Yantao Zhao, Pei Wang, Mohamed Ahmedna, Chi-Tang Ho, and Shengmin Sang Chemical Research in Toxicology 2015 28 (1), 135-143
AbstractGrowing evidence has shown that ascorbic acid (ASA) can contribute to protein glycation and the formation of advanced glycation end products (AGEs), especially in the lens. The mechanism by which ascorbic acid can cause protein glycation probably originates from its oxidized form, dehydroascorbic acid (DASA), which is a reactive dicarbonyl species. In the present study, we demonstrated for the first time that four tea flavanols, (−)-epigallocatechin 3-O-gallate (EGCG), (−)-epigallocatechin (EGC), (−)-epicatechin 3-O-gallate (ECG), and (−)-epicatechin (EC), could significantly trap DASA and consequently form 6C- or 8C-ascorbyl conjugates. Among these four flavanols, EGCG exerted the strongest trapping efficacy by capturing approximate 80% of DASA within 60 min. We successfully purified and identified seven 6C- or 8C-ascorbyl conjugates of flavanols from the chemical reaction between tea flavanols and DASA under slightly basic conditions. Of which, five ascorbyl conjugates, EGCGDASA-2, EGCDASA-2, ECGDASA-1, ECGDASA-2 and ECDASA-1, were recognized as novel compounds. The NMR data showed that positions 6 and 8 of the ring A of flavanols were the major active sites for trapping DASA. We further demonstrated that tea flavanols could effectively inhibit the formation of DASA-induced AGEs via trapping DASA in the bovine lens crystallin-DASA assay. In this assay, 8C-ascorbyl conjugates of flavanols were detected as the major adducts using LCMS. This study suggests that daily consumption of beverages containing tea flavanols may prevent protein glycation in the lens induced by ascorbic acid and its oxidized products.
SponsorQatar National Research Fund NPRP no. 5-220-3-063
PublisherAmerican Chemical Society
TitleTea flavanols block advanced glycation of lens crystallins induced by dehydroascorbic acid
Issue Number1
Volume Number28

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