Nonvolatile metabolite alteration and protective potential on HOEC against nicotine during Zijuan black tea processing

Understanding nonvolatile metabolite alterations during processing and their impacts on potential function is crucial for technological innovations in tea manufacture. In the present work, specific metabolite alterations during Zijuan black tea processing and their potential effects on nicotine-induced human oral epithelial cell (HOEC) injury were investigated. The results showed leucine, isoleucine, and tyrosine, etc. were the main hydrolysis products during withering, and theaflavin-3-gallate (TF-3-G), theaflavin-3’-gallate (TF-3’-G) and theaflavin-3,3’-gallate (TFDG) were mainly formed during rolling. And oxidation of flavonoid glycosides, catechins and dimeric catechins took place during fermentation. When coming to drying, amino acid conversion became dominant. Meanwhile, processing samples effectively attenuated nicotine-induced oxidative stress and inflammation in HOEC. TF-3’-G, TF-3-G, phenylalanine, and kaempferol-3-coumaroyglucoside, etc. exhibited strong associations with the protective action, which indicates that by modifying the processes in which black tea are produced to be rich in those specific components could be beneficial for the oral health of the smoking people.