Effect of yellowing time on bioactive compounds in yellow tea and their antiproliferative capacity in HepG2 cells

Abstract

Several studies have shown potent antineoplastic effects of tea, which can induce apoptosis and inhibit proliferation of cancer cells. Yellow tea is one of the six major types of tea, and yellowing time, a key factor in its processing, is known to improve its quality and bioactivity. However, the effects of yellowing on the composition of the bioactive substances of tea are poorly understood. We analyzed the biochemical composition and the antioxidant and anticancer activities of the extracts of yellow tea (EYTs) subjected to different yellowing durations. Prolonged yellowing increased the content of water extracts, amino acids, soluble sugars, theaflavins, and nonesterified catechins ( p < 0.05, p < 0.01) and decreased that of polyphenols, flavonols, thearubigins, caffeine, GA, and esterified catechins ( p < 0.05, p < 0.01). In addition, yellowing also slightly increased the antioxidant capacity of the EYTs, but did not significantly affect their ability to inhibit the proliferation of the hepatocarcinoma HepG2 cells. Mechanistically, the EYTs significantly downregulated the phosphorylation of PI3K and AKT and upregulated the Bax/Bcl‐2 ratio in the HepG2 cells. Taken together, the yellowing time influences the bioactive components of yellow tea, and the resulting yellow tea may have more potent antioxidant and anticancer effects.

Characterization of Roasting Time on Sensory Quality, Color, Taste, and Nonvolatile Compounds of Yuan An Yellow Tea

“…Roasting is an important manufacturing procedure and involves the development of sensory quality. There has been much roasting research involved in large-leaf yellow tea [9][10][11][12]; for instance, the old fire roasting was essential for the formation of large-leaf yellow tea flavor with strong roasted, nutty, woody odors and weak fatty, fruity odors, and retaining high levels of gallocatechin gallate (GCG), total volatiles and heterocyclic compounds [10]. However, until now, few studies have been concerned with the effect of roasting time on sensory quality, color, taste, and nonvolatile compounds of YAYT.…”

The Effect of Yellow Tea Leaves Camellia sinensis on the Quality of Stored Chocolate Confectionery

“…Results indicate that yellowing time, a key factor in yellow tea processing, improves quality and biological activity of the final product [75,76]. Yellow tea has numerous health-promoting values, which mainly come from the presence of flavonoids and offer antioxidant, antihyperglycemic, antihyperlipidemic, and anticancer activity [75,[77][78][79][80]. Yellow tea exhibits strong antioxidant activity in in vitro systems, e.g., fats, emulsions, foods and other systems [39,58,[80][81][82].…”

“…The main active components of tea leaves are flavan-3-ols, phenolic acids, tannins (condensed and hydrolysable), and purine alkaloids, which after processing go through several steps leading to the formation of theaflavins, thearubigins, and flavan-3-ols derivatives with a corresponding decrease in catechins concentrations [74]. Results indicate that yellowing time, a key factor in yellow tea processing, improves quality and biological activity of the final product [75,76]. Yellow tea has numerous health-promoting values, which mainly come from the presence of flavonoids and offer antioxidant, antihyperglycemic, antihyperlipidemic, and anticancer activity [75,[77][78][79][80].…”

Tea as a natural gift for discovering antiviral candidates

“…The initial process is the same as that of green tea regarding to roasting or steaming, and it then requires a unique step known as “sealed yellowing” that can remove the grassy flavor of green tea while still retaining the healthcare values [16] . Prolonged yellowing has been reported to increase the contents of amino acids, soluble sugar, TFs, and non-esterified catechins while decreasing the contents of polyphenols, flavonols, thearubigins, caffeine, and esterified catechins [17] . In particular, the ester catechin content in yellow tea was significantly lower than that in green tea, and the content of non-esterified catechins and amino acids was higher than that in green tea.…”