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Herein, DhC2-1 was isolated and identified as an unstable mixture of an isomer of the epicatechin oxidative dimer DhC2-4 and intermediate IV (DhC2-1b), while this mixture readily degraded to DhC2-1a. Nuclear magnetic resonance (NMR) analysis established DhC2-4 as a \u03b3AB-type dehydrodicatechin possessing a unique C\u2013tetrahydropyran\u2013cyclohexenone\u2013tetrahydrofuran\u2013A ring linkage. To explore a possible structural relationship with thearubigins (TRs), a TR fraction TR13\u201319, purified from Keemun black tea, was acid-hydrolyzed; the resulting hydrolysate (m\/z 575.1234 [M\u2013H]\u2212) exhibited LC retention similar to that of DhC2-1 and DhC2-4. Furthermore, characteristic 13C NMR signals of TR13\u201319 at \u03b4C 194.40, 165.06\u2013165.19, 94.41, and 41.29 ppm matched those of DhC2-4, suggesting that \u03b3AB-type dehydrodicatechins may be structurally related to TRs.<\/jats:p>","DOI":"10.1021\/acs.jafc.6c07994","type":"journal-article","created":{"date-parts":[[2026,7,27]],"date-time":"2026-07-27T10:35:01Z","timestamp":1785148501000},"page":"23726-23740","source":"Crossref","is-referenced-by-count":0,"title":["Epicatechin Oxidation Dimers Produced by Crude Tea\nEnzymes: Isolation, Structural Elucidation, and Potential Link to\nThearubigin Formation"],"prefix":"10.1021","volume":"74","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3285-9480","authenticated-orcid":true,"given":"Mingchun","family":"Wen","sequence":"first","affiliation":[{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]},{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8986-7027","authenticated-orcid":true,"given":"Lu","family":"Li","sequence":"additional","affiliation":[{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]},{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wei","family":"Hu","sequence":"additional","affiliation":[{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]},{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xuanrong","family":"Huang","sequence":"additional","affiliation":[{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]},{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zisheng","family":"Han","sequence":"additional","affiliation":[{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]},{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]},{"name":"Anhui Agricultural University\u2019s Comprehensive Experimental Station in the Northwest of Anhui Province , , , ,","place":["Linquan, Anhui, China, 236400"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2279-2657","authenticated-orcid":true,"given":"Liang","family":"Zhang","sequence":"additional","affiliation":[{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]},{"name":"Anhui Agricultural University , , ,","place":["Hefei, China, 230036"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,7,27]]},"reference":[{"key":"2026080510091522600_cit1","doi-asserted-by":"publisher","DOI":"10.1016\/j.fbio.2025.107332","article-title":"Dynamic changes in metabolic\ncompounds and their effects on flavor\nquality of Fuliang black tea and green tea during processing","volume":"71","author":"Dong","year":"2025","journal-title":"Food Biosci."},{"key":"2026080510091522600_cit2","doi-asserted-by":"publisher","first-page":"347","DOI":"10.1016\/j.foodchem.2019.01.174","article-title":"Tea aroma formation\nfrom six model manufacturing processes","volume":"285","author":"Feng","year":"2019","journal-title":"Food\nChem."},{"key":"2026080510091522600_cit3","doi-asserted-by":"publisher","DOI":"10.1016\/j.foodchem.2024.138680","article-title":"Effects of fermentation\nduration on the flavour quality of large\nleaf black tea based on metabolomics","volume":"444","author":"Dong","year":"2024","journal-title":"Food Chem."},{"issue":"13","key":"2026080510091522600_cit4","doi-asserted-by":"publisher","first-page":"3402","DOI":"10.1021\/acs.jafc.7b06044","article-title":"Novel Theaflavin-Type Chlorogenic\nAcid Derivatives Identified in\nBlack Tea","volume":"66","author":"Zhang","year":"2018","journal-title":"J. Agric. Food Chem."},{"issue":"26","key":"2026080510091522600_cit5","doi-asserted-by":"publisher","first-page":"5417","DOI":"10.1021\/acs.jafc.6b01896","article-title":"Reactions of Flavonoids with o-Quinones Interfere with\nthe Spectrophotometric Assay of Tyrosinase Activity","volume":"64","author":"Ga\u0328sowska-Bajger","year":"2016","journal-title":"J. Agric. 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Int."},{"issue":"30","key":"2026080510091522600_cit30","doi-asserted-by":"publisher","first-page":"6011","DOI":"10.1021\/acs.jafc.6b01695","article-title":"Annotation\nof Different Dehydrocatechin\nOligomers by MS\/MS and Their Occurrence in Black Tea","volume":"64","author":"Verloop","year":"2016","journal-title":"J. Agric. Food Chem."},{"issue":"47","key":"2026080510091522600_cit31","doi-asserted-by":"publisher","first-page":"13879","DOI":"10.1021\/acs.jafc.0c05716","article-title":"Browning\nof Epicatechin (EC) and Epigallocatechin (EGC) by Auto-Oxidation","volume":"68","author":"Tan","year":"2020","journal-title":"J. Agric. Food Chem."},{"issue":"5","key":"2026080510091522600_cit32","doi-asserted-by":"publisher","first-page":"1051","DOI":"10.3390\/molecules25051051","article-title":"Production of Ellagitannin\nHexahydroxydiphenoyl Ester by Spontaneous Reduction of Dehydrohexa-hydroxydiphenoyl\nEster","volume":"25","author":"Era","year":"2020","journal-title":"Molecules"},{"issue":"5","key":"2026080510091522600_cit33","doi-asserted-by":"publisher","first-page":"669","DOI":"10.1016\/S0731-7085(98)00290-8","article-title":"Peak fronting in\nreversed-phase high-performance liquid chromatography: a study of\nthe chromatographic behavior of oxycodone hydrochloride","volume":"19","author":"Brogle\u0301","year":"1999","journal-title":"J. Pharm. Biomed."},{"issue":"6712","key":"2026080510091522600_cit34","doi-asserted-by":"publisher","first-page":"661","DOI":"10.1038\/25322","article-title":"Polysaccharide\nelasticity governed by chair\u2013boat transitions of the glucopyranose\nring","volume":"396","author":"Marszalek","year":"1998","journal-title":"Nature"},{"issue":"9","key":"2026080510091522600_cit35","doi-asserted-by":"publisher","first-page":"2165","DOI":"10.1021\/jf204497b","article-title":"Epicatechin-3-O-(3\u2032\u2019-O-methyl)-gallate\nContent in Various Tea Cultivars (Camellia sinensis L.) and Its in Vitro Inhibitory Effect on Histamine Release","volume":"60","author":"Maeda-Yamamoto","year":"2012","journal-title":"J. Agric. Food Chem."},{"issue":"1","key":"2026080510091522600_cit36","doi-asserted-by":"publisher","first-page":"77","DOI":"10.1248\/cpb.37.77","article-title":"Tannins and\nRelated Compounds. LXXVII.:\nNovel Chalcan-flavan Dimers, Assamicains A, B and C, and a New Flavan-3-ol\nand Proanthocyanidins from the Fresh Leaves of Camella sinensis L. var. assamica KITAMURA","volume":"37","author":"Hashimoto","year":"1989","journal-title":"Chem. Pharm. Bull."},{"issue":"6","key":"2026080510091522600_cit37","doi-asserted-by":"publisher","first-page":"1383","DOI":"10.1248\/cpb.40.1383","article-title":"Tannins and\nRelated Compounds. CXIV.\nStructure of Novel Fermentation Products, Theogallinin, Theaflavonin\nand Desgalloyl Theaflavonin from Black Tea, and Changes of Tea Leaf\nPolyphenols during Fermentation","volume":"40","author":"Hashimoto","year":"1992","journal-title":"Chem. Pharm.\nBull."},{"issue":"1","key":"2026080510091522600_cit38","doi-asserted-by":"publisher","DOI":"10.1038\/srep08742","article-title":"Analysis\nof accumulation patterns and preliminary study on the condensation\nmechanism of proanthocyanidins in the tea plant [Camellia sinensis]","volume":"5","author":"Jiang","year":"2015","journal-title":"Sci. Rep."},{"issue":"5","key":"2026080510091522600_cit39","doi-asserted-by":"publisher","DOI":"10.1111\/1541-4337.70249","article-title":"Flavone Glycosides\nof Tea: Structure, Isolation, Identification, Health Benefit and Sensory\nProperty","volume":"24","author":"Ke","year":"2025","journal-title":"Compr. Rev. Food Sci. Food Saf."},{"issue":"5","key":"2026080510091522600_cit40","doi-asserted-by":"publisher","first-page":"1279","DOI":"10.1016\/0031-9422(96)00127-6","article-title":"Structural determination of colourless\nand yellow dimers resulting from (+)-catechin coupling catalysed by\ngrape polyphenoloxidase","volume":"42","author":"Guyot","year":"1996","journal-title":"Phytochemistry"},{"issue":"3","key":"2026080510091522600_cit41","doi-asserted-by":"publisher","first-page":"273","DOI":"10.3390\/molecules21030273","article-title":"Structure Determination of Novel\nOxidation Products from Epicatechin: Thearubigin-Like Molecules","volume":"21","author":"Uchida","year":"2016","journal-title":"Molecules"},{"issue":"5","key":"2026080510091522600_cit42","doi-asserted-by":"publisher","first-page":"777","DOI":"10.1002\/ejoc.202001579","article-title":"Stereochemistry\nof\na Cyclic Epicatechin Trimer with C3 Symmetry Produced by Oxidative Coupling","volume":"2021","author":"Kawazoe","year":"2021","journal-title":"Eur. J. Org. Chem."},{"issue":"7","key":"2026080510091522600_cit43","doi-asserted-by":"publisher","first-page":"2142","DOI":"10.1021\/jf011301a","article-title":"Synthesis\nof Theaflavin from Epicatechin and Epigallocatechin by Plant Homogenates\nand Role of Epicatechin Quinone in the Synthesis and Degradation of\nTheaflavin","volume":"50","author":"Tanaka","year":"2002","journal-title":"J. Agric. Food Chem."}],"container-title":["Journal of Agricultural and Food Chemistry"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.jafc.6c07994","content-type":"application\/pdf","content-version":"vor","intended-application":"unspecified"},{"URL":"https:\/\/pubs.acs.org\/jafcau\/article-pdf\/74\/30\/23726\/66279420\/acs.jafc.6c07994.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.acs.org\/jafcau\/article-pdf\/74\/30\/23726\/66279420\/acs.jafc.6c07994.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T14:31:19Z","timestamp":1785940279000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.acs.org\/jafcau\/article\/74\/30\/23726\/5233913\/Epicatechin-Oxidation-Dimers-Produced-by-Crude-Tea"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,7,27]]},"references-count":43,"journal-issue":{"issue":"30","published-online":{"date-parts":[[2026,7,27]]},"published-print":{"date-parts":[[2026,8,5]]}},"URL":"https:\/\/doi.org\/10.1021\/acs.jafc.6c07994","relation":{},"ISSN":["0021-8561","1520-5118"],"issn-type":[{"value":"0021-8561","type":"print"},{"value":"1520-5118","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,7,27]]}}}