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Global Natural Product Social feature-based networking was applied to follow the phytochemicals, including nine flavonoid glycosides, six catechins, and three flavonols in Huangjinya green tea. Further, a new 8-O-4'-type neolignan glycoside, camellignanoside A (1), and 15 known compounds (2-16) were isolated through a variety of column chromatographies, and the structure was elucidated extensively by ultra performance liquid chromatography-quadrupole-time-of-flight-tandem mass spectrometry, 1H and 13C nuclear magnetic resonance, heteronuclear single-quantum correlation, heteronuclear multiple-bond correlation, 1H-1H correlation spectroscopy, rotating frame nuclear Overhauser effect spectroscopy, and Nuclear Overhauser effect spectroscopy, and circular dichroism spectroscopies. Compounds 1 and 2 showed acetylcolinesterase inhibition activity, with IC50 = 0.75 and 0.18 μM, respectively.

Zijuan tea ( Camellia sinensis var. assamica), an anthocyanin-rich cultivar with purple leaves, is a valuable material for manufacturing tea with unique color and flavor. In this paper, four new phenylpropanoid substituted epicatechin gallates (pECGs), Zijuanins A-D (1-4), were isolated from Zijuan green tea by different column chromatography. Their structures were identified by extensive high resolution mass spectroscopy (HR-MS), nuclear magnetic resonance (NMR), and experimental and calculated circular dichroism (CD) spectroscopic analyses. Detection of the changes in fresh tea leaves collected from April to September and the final processed product by high performance liquid chromatography (HPLC)-HRMS suggested that production of compounds 1 and 2 may be enhanced by the processing procedure of Zijuan green tea. Additionally, 1-4 were proposed to be synthesized through interaction between the abundant secondary metabolite ECG and phenolic acids from tea leaves by two key steps of phenol-dienone tautomerism. 1 and 2 showed impressive activity in protecting SH-SY5Y cells against H2O2-induced damage at the concentration of 1.0 μM.

Green tea may favorably modulate blood glucose homeostasis, and regular consumption of green tea can prevent the development of type 2 diabetes mellitus. In this study, α-glucosidase and α-amylase inhibitory effects of the novel acylated flavonol tetraglycoside (camellikaempferoside C, 1) and 14 other flavone and flavone glycosides (FGs) isolated from Lu'an GuaPian (Camellia sinensis L.O. Kuntze) were evaluated. The kaempferol monoglycoside (15) showed inhibitory activity against α-glucosidase with IC50 at 40.02 ± 4.61 μM, and kaempferol diglycoside (13) showed α-amylase inhibition with IC50 at 0.09 ± 0.02 μM. Further, inhibitory mechanisms of FGs 15 and 13 were studied by molecular docking analysis and fluorescence spectrometry. Molecular docking suggested that FG 15 interacted with α-glucosidase mainly by hydrogen bonding, which was the same interaction force between FG 13 and α-amylase. Intrinsic fluorescence of α-glucosidase and α-amylase was quenched by 15 and 13, respectively, through a static quenching mechanism. The spontaneous formation of 15-α-glucosidase and 13-α-amylase complexes was driven by van der Waals forces and hydrogen bonding. The present study provides new insight into the potential application of Lu'an GuaPian green tea as a functional food ingredient to regulate postprandial hyperglycemia through inhibition of α-glucosidase/α-amylase by FGs, particularly the mono− and di− glycosides of kaempferol.