Chinese Xi-Gui tea is one ancient cultivated variety of Camellia sinensis var. assamica. At present, it is used for producing expensive and elite tea in China. Five new flavoalkaloids, (-)-6-(5''' S)- N-ethyl-2-pyrrolidinone-epicatechin-3- O-gallate (ester-type catechins pyrrolidinone E, etc-pyrrolidinone E, 1), (-)-6-(5''' R)- N-ethyl-2-pyrrolidinone-epicatechin-3- O-gallate (etc-pyrrolidinone F, 2) (-)-8-(5''' S)- N-ethyl-2-pyrrolidinone-epicatechin-3- O-gallate (etc-pyrrolidinone G, 3a), (-)-8-(5''' S)- N-ethyl-2-pyrrolidinone-catechin-3- O-gallate (etc-pyrrolidinone I, 4a), (-)-8-(5''' R)- N-ethyl-2-pyrrolidinone-catechin-3- O-gallate (etc-pyrrolidinone J, 4b), and one new naturally occurring natural product (-)-8-(5''' R)- N-ethyl-2-pyrrolidinone-epicatechin-3- O-gallate (etc-pyrrolidinone H, 3b) together with the known flavoalkaloids etc-pyrrolidinones A-D (5, 6, 7a, and 7b) were detected and isolated from Xi-Gui green tea. Their structures were identified by comprehensive NMR spectroscopic analyses. Absolute configurations of 1-3 were established by comparison of the CD analyses with epicatechin-3- O-gallate (ECG). Compounds 1-4 were evaluated for their protection against high glucose induced cell senescence on human umbilical vein endothelia cells (HUVECs) and showed significant protection effects ( p < 0.01) at both 1.0 and 10 μM. A discussion on the possible evolution of tea plants divergent from related food plants on the basis of phytochemical view is also provided.

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concentrations of the substrates were 0.010 or 0.020 M. In the conductimetric method 10-20 pL of a 10% solution of a substrate in dioxane, THF, or hexane, all containing 0.025 M 2,6-lutidine, was injected into a thermally equilibrated and magnetically stirred solvent (20 mL) placed in a conductivity cell (cell constant 0.1005). The temperature of the thermostat (kerosene) was maintained within ±0.05 °C during the measurement. The conductivity changes followed a good first-order kinetics. The acetolysis and formolysis were conducted in the presence of 0.0250 M sodium acetate or sodium formate, respectively, and the rates followed by titrating the unreácted base with 0.01 M HC104-acetic acid by using crystal violet as an indicator. For quenching of an aliquot, carbon tetrachloride in acetolysis and acetic acid in formolysis were used. For titrimetric runs at 25.0 °C, a pipet-out method was used, whereas for those at 50.0,75.0, and 100.0 °C, an ampule technique was employed.

A series of binuclear ruthenium vinyl complexes with dithienylethene units, [RuCl(CO)(PMe3)3]2(μ-CHCH-DTE-CHCH) (5a, 5b), [RuCl(CO)(Py)(PPh3)2]2(μ-CHCH-DTE-CHCH) (6a, 6b), [RuTp(CO)(PPh3)]2(μ-CHCH-DTE-CHCH) (7a, 7b), and [RuCl(CO)(PMP)]2(μ-CHCH-DTE-CHCH) (8a, 8b) (DTE = 1,2-bis(2-methylthiophen-3-yl)cyclopentene; 1,2-bis(2-methylthiophen-3-yl)-3,3,4,4,5,5-hexafluorocyclopentene), have been prepared. The respective products have been characterized by elemental analyses, NMR spectrometry, and UV/vis spectrophotometry. The structures of 3a and 5b have been established by X-ray crystallography. It is revealed that the binuclear ruthenium vinyl complexes with dithienylethene units show photochromic behavior, but their absorption spectra, cyclization/cycloreversion quantum yields, and the efficiency of the photochromic process are highly dependent on the central switching units and the ancillary ligands attached to the metal. Electrochemical studies have shown that the open-ring isomers of the metal complexes are triggered, either by light or electricity, to convert to their closed forms. It has clearly been demonstrated that these complexes represent a class of light- and electrotriggered multifunctional switch molecules featuring electrochromism, electrocyclization, and photo/electrotuning of the electronic communication.