Selenium-Mediated (-)-Epigallocatechin-3-Gallate Dynamics via Regulation of Flavonoid Biosynthesis in Fu Tea ( (L.) O. Kuntze).

Tea ( (L.) O. Kuntze) is a highly selenium enrichment capacity plant; high selenium concentration contributes to the occurrence of oxidative stress and protein misfolding in tea plants, whereas flavonoids can chelate heavy metals to protect plants from oxidative stress caused by metal exposure. Nevertheless, the role of catechins in flavonoid synthesis and nutrient metabolism under selenium stress remains unidentified. Combining Word2vec and HNSW utilizing UHPLC-Q-Orbitrap HRMS-MS/MS to implement rapid matching annotation of the structural information on metabolites in Fu tea, we found that selenium-mediated changes in catechins in Fu tea were mainly associated with flavonoid biosynthesis pathways. The results demonstrated that selenium treatment increased benign selenol analogues (glutathioselenol) in tea and identified the novel selenopeptide PRSeMW (/ 636.22571, Pro-Arg-SeMet-Trp) in selenium-enriched Fu tea samples to enhance the health benefits of tea. The selenium levels were negatively correlated with -ethyl-l-glutamine (11.63 to 4.26 mg kg) and (-)-epigallocatechin (13.26 to 11.19 mg kg), increasing the accumulation of tea polyphenols ((-)-catechin gallate, (-)-epigallocatechin 3-gallate, and (+)-gallocatechin), and decreasing the level of caffeine. These discoveries provide new insights into the mechanism of tea polyphenol-mediated transformation of selenium in Fu tea and theoretical support for the quality assessment of selenium-enriched tea.