Preventive effects of C-2 epimeric isomers of tea catechins on mouse type I allergy.

The preventive effects of C-2 epimeric isomers of (-)-epigallocatechin-3-O-gallate (EGCG) and the O-methylated derivative, (-)-epigallocatechin-3-O-(3-O-methyl)gallate (EGCG3''Me), against ovalbumin-induced type I allergy in male mice were investigated. EGCG and EGCG3''Me exhibited strong antiallergic effects by oral administration at doses of 25 and 50 mg/kg body weight. The antiallergic effects of their C-2 epimers, (-)-gallocatechin-3-O-gallate and (-)-gallocatechin-3-O-(3-O-methyl)gallate (GCG3''Me), on mouse type I allergy were almost equivalent to and/or as strong as those of the corresponding original catechins, respectively.

Preventive effects of black tea theaflavins against mouse type IV allergy.

Background: Tea (Camellia sinensis L.), one of the most popular beverages, contains various beneficial constituents. We investigated the preventive effects of black tea theaflavins, theaflavin-3-gallate (3-TF) and theaflavin-3,3'-digallate (TFDG), on oxazolone-induced type IV allergy in male ICR mice.

Determination of theaflavins including methylated theaflavins in black tea leaves by solid-phase extraction and HPLC analysis.

A quantitative method for four theaflavins and two methylated theaflavin derivatives in black tea leaves was developed by solid-phase extraction and a high-performance liquid chromatographic method with photodiode array detection. The theaflavins in black tea leaves were extracted three times with 40 vol 50% aqueous ethanol (mg dry tea powder/mL) containing 2% ascorbic acid. The ethanol extracts were diluted 4-fold with distilled water.

Inhibitory Effects of the C-2 Epimeric Isomers of Tea Catechins on Mouse Type IV Allergy.

The inhibitory effects of C-2 epimeric isomers of (-)-epigallocatechin-3-O-gallate (EGCG) and two O-methylated EGCG derivatives, (-)-epigallocatechin-3-O-(3-O-methyl)gallate (EGCG3''Me) and (-)-epigallocatechin-3-O-(4-O-methyl)gallate (EGCG4''Me), against oxazolone-induced type IV allergy in male mice were investigated. These compounds exhibited strong antiallergic effects by percutaneous administration at a dose of 0.13 mg/ear.

[Suppression of glucose absorption by various health teas in rats].

The inhibitory effects on the intestinal digestion and absorption of sugar of health teas that claim beneficial dietary and diabetes-controlling effects were compared in rats using portal cannulae. The measured durations were the times during which the elevation of portal glucose levels resulting from continuous intragastric infusion of sucrose or maltose was suppressed by concentrated teas. The teas investigated included salacia oblonga, mulberry, guava, gymunema, taheebo, yacon, and banaba.

O-methylated catechins from tea leaves inhibit multiple protein kinases in mast cells.

Tea contains a variety of bioactive compounds. In this study, we show that two O-methylated catechins, (-)-epigallocatechin-3-O-(3-O-methyl) gallate and (-)-epigallocatechin-3-O-(4-O-methyl) gallate, inhibit in vivo mast cell-dependent allergic reactions more potently than their nonmethylated form, (-)-epigallocatechin-3-O-gallate. Consistent with this, these O-methylated catechins inhibit IgE/Ag-induced activation of mouse mast cells: histamine release, leukotriene release, and cytokine production and secretion were all inhibited.

Determination of peroxyl radical scavenging activity of flavonoids and plant extracts using an automatic potentiometric titrator.

A novel potentiometric method for evaluation of peroxyl radical scavenging activity of flavonoids and plant extracts was developed. The oxidation of potassium iodide (KI) was performed in acetonitrilephosphate buffer (1:1) containing antioxidant using 2,2'-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator. The amount of iodine released from KI during a 20-min free radical oxidation was determined quantitatively using an automatic potentiometric titrator with sodium thiosulfate.

Association of suppression of extracellular signal-regulated kinase phosphorylation by epigallocatechin gallate with the reduction of matrix metalloproteinase activities in human fibrosarcoma HT1080 cells.

Matrix metalloproteinases (MMPs) play a crucial role in the process of cancer invasion and metastasis. Previous findings suggested that epigallocatechin gallate (EGCG), a main flavanol of green tea, caused decreased levels of MMP-2 and MMP-9 activities to be secreted into culture medium. To obtain further information on EGCG-mediated regulation of these MMPs, the effects of EGCG on enzyme activity, mRNA expression, and mitogen-activated protein kinase (MAPK) activities in human fibrosarcoma HT1080 cells were examined.

Epimerization of tea catechins and O-methylated derivatives of (-)-epigallocatechin-3-O-gallate: relationship between epimerization and chemical structure.

Epimerization at C-2 of O-methylated catechin derivatives and four major tea catechins were investigated. The epimeric isomers of (-)-epicatechin (I), (-)-epicatechin-3-O-gallate (II), (-)-epigallocatechin (III), (-)-epigallocatechin-3-O-gallate (IV), and (-)-epigallocatechin-3-O-(3-O-methyl)gallate (V) in green tea extracts increased time-dependently at 90 degrees C. The epimerization rates of authentic tea catechins in distilled water are much lower than those in tea infusion or in pH 6.

Antiallergic tea catechin, (-)-epigallocatechin-3-O-(3-O-methyl)-gallate, suppresses FcepsilonRI expression in human basophilic KU812 cells.

We previously found that the O-methylated derivative of (-)-epigallocatechin-3-O-gallate (EGCg), (-)-epigallocatechin-3-O-(3-O-methyl)-gallate (EGCG' '3Me), has potent antiallergic activity. The high-affinity IgE receptor, FcepsilonRI, is found at high levels on basophils and mast cells and plays a key role in a series of acute and chronic human allergic reactions. To understand the mechanism of action for the antiallergic EGCG' '3Me, the effect of EGCG' '3Me on the cell surface expression of FcepsilonRI in human basophilic KU812 cells was examined.

Prolyl endopeptidase inhibitors from the roots of Lindera strychnifolia F. Vill.

Prolyl endopeptidase (PEP, EC 3.4.21.