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Epigallocatechin (EGC) esters as potential sources of antioxidants

Ambigaipalan, Priyatharini, Oh, Won Young, Shahidi, Fereidoon
Food chemistry 2020 v.309 pp. 125609
2,2-diphenyl-1-picrylhydrazyl, acylation, antioxidant activity, antioxidants, carbon, cations, docosahexaenoic acid, dodecanoic acid, epigallocatechin, esters, high performance liquid chromatography, hydrophilicity, lipophilicity, mass spectrometry, nuclear magnetic resonance spectroscopy, octanoic acid, propionic acid, stable isotopes, stearic acid
Epigallocatechin (EGC) was acylated with selected fatty acids, namely propionic acid [C3:0], caprylic acid [C8:0], lauric acid [C12:0], stearic acid [C18:0]) and docosahexaenoic acid (DHA)[C22:6n-3] in order to increase its lipophilicity. Monoesters were identified as the predominant products (~40%) followed by diesters (~33%), triesters (~9%) and trace amounts of tetra- and pentaesters. ¹H NMR, ¹³C NMR and HPLC-DAD-MS were used to elucidate the acylation sites and structures of new EGC esters. According to the HPLC-MS analysis of the caprylate esters, EGC-4′-O-caprylate (27%), EGC-3′-O-caprylate or EGC-5′-O-caprylate (12%) and EGC-3′,5′-O-dicaprylate (16%) were the major compounds generated upon the acylation reaction of EGC. The acylation significantly increased the lipophilicity of EGC. In addition, EGC and its esters showed radical scavenging activities against DPPH radical and ABTS radical cation. Therefore, EGC esters could serve as potential sources of antioxidants for application in both hydrophilic and lipophilic media.