Isolation and structural elucidation of dimeric epigallocatechin-3-gallate autoxidation products and their antioxidant capacity

Abstract Dietary polyphenols like epigallocatechin-3-gallate (EGCG)—which represents the most abundant flavan-3-ol in green tea—are subject of several studies regarding their bioactivity and health-related properties. On many occasions, cell culture or vitro experiments form basis published data. Although stability these compounds is observed to be low, reported effects are directly related parent whereas impact EGCG degradation autoxidation products not yet understood merely studied. its dimers theasinensin A D, “P2” oolongtheanin characterized same extent as parental polyphenol. However, investigate products—which would minimize discrepancy between vivo data—isolation structure elucidation techniques urgently needed. In this study, a new protocol acquire D well depicted, including variety spectroscopic quadrupole time-of-flight high-resolution mass spectrometric (qTOF-HRMS) data characterize assign isolates. Through nuclear magnetic resonance (NMR) spectroscopy, polarimetry, especially circular dichroism (CD) spectroscopy after enzymatic hydrolysis complementary atropisomeric stereochemistry isolated theasinensins illuminated elucidated. Lastly, direct comparison monomer itself carried out antioxidant properties featuring Trolox equivalent capacity (TEAC) values. These findings help cellular and—which special interest flavonoid group—their redox