Green, Black and Rooibos Tea Inhibit Prostaglandin E2 Formation in Human Monocytes by Inhibiting Expression of Enzymes in the Prostaglandin E2 Pathway

The formation of prostaglandin E2 (PGE2) is associated with adverse inflammatory effects. However, long-term treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) comes with risk of severe side effects. Therefore, alternative ways to inhibit PGE2 are warranted. We have investigated the effects of tea extracts and the polyphenols epigallocatechin gallate (EGCG) and quercetin on PGE2 formation, determined by immunoassay, and protein expression, determined by immunoblotting, of cytosolic phospholipase A2 (cPLA2), cyclooxygenase 2 (COX-2) and microsomal PGE synthase-1 (mPGES-1) in human monocytes. Green and black tea extracts, and with a lower potency, Rooibos tea extract, inhibited lipopolysaccharide (LPS) and calcium ionophore-induced PGE2 formation. In addition, all tea extracts inhibited the LPS-induced expression of mPGES-1, and the green and black tea extracts also inhibited, to a lesser extent, COX-2 expression. The tea extracts only marginally reduced cPLA2 expression and had no effect on COX-1 expression. EGCG, present in green and black tea, and quercetin, present in all three teas, also inhibited PGE2 formation and expression of mPGES-1, COX-2 and cPLA2. Cell-based and cell-free assays were also performed to evaluate direct effects on the enzymatic activity of COX and PGE synthases. Mainly, the cell-free assay demonstrated partial inhibition by the tea extracts and polyphenols. However, the inhibition required higher doses compared to the effects demonstrated on protein expression. In conclusion, green and black tea, and to a lesser extent Rooibos tea, are potent inhibitors of PGE2 formation in human monocytes, and mediate their effects by inhibiting the expression of the enzymes responsible for PGE2 formation, especially mPGES-1.

Effect of Black and Green Tea on Salivary pH: a Double Blinded Cross-Over Study

Background: Some herbal products could affect on salivary pH and prevention of dental caries. Tea consumption has inhibition effects on some oral bacteria. Objective: The aim of this study was to evaluate the effect of green and black tea on salivary pH. Material and Methods: In this double blinded cross-over trial, salivary samples of 50 healthy male students of Zahedan Faculty of Dentistry, aged 20-22 years old were collected for evaluation of salivary pH. All volunteers were asked to consume commercially black tea on the first day and then saliva samples were collected before drinking tea and immediately after drinking tea and 5 and 10 minutes after tea consumption. With replacing consumption of green tea, at the second day, saliva samples were collected again. Then the salivary pH was estimated with a digital pH-meter. Data were analyzed through independent t-test and paired samples t-test. Results: Mean salivary pH before and after green tea consumption were 7.15±0.05 and 7.56±0.09, respectively, which showed a remarkable difference (p<0.001). It was 7.14±0.05 and 7.51 ± 0.10, respectively, for black tea, with significant difference (p<0.0001). Mean salivary pH after green tea consumption was significantly higher than black tea (p= 0.006). Conclusion: Both green and black tea intake led to a significant rise in salivary pH, which was higher after green tea consumption compared to black tea. This study suggests the beneficial effects of drinking tea in providing an alkaline environment in oral cavity. KEYWORDS Black tea; Green tea; Saliva; pH.

The Effect of Water Mineralization on the Extraction of Active Compounds from Selected Herbs and on the Antioxidant Properties of the Obtained Brews

The objective of the study was to analyze the effect of total content of minerals in waters on the effectiveness of extraction of polyphenols and flavonoids and on the antioxidant properties of brews from leaves of green and black tea, leaves of peppermint, chamomile inflorescences, leaves of sage, and flowers of lavender. The process of brewing was conducted at an initial temperature of 95 °C, under cover, for 15 min, with the use of 10 waters differing in terms of mineral components. The content of total polyphenols and total flavonoids was determined in the brews obtained. The antioxidant properties were assayed with the use of stable DPPH radicals and Ferric Reducing Antioxidant Power (FRAP) reagent. A significant effect of water mineralization on the extraction of phenolic compounds and on the antioxidant properties of the brews obtained was observed. In the majority of cases, the highest concentrations of polyphenols and flavonoids were obtained in brews prepared with the use of deionized water and waters with medium levels of mineralization. It was also demonstrated that there was a significant reduction of antioxidant properties in brews prepared with the water that had the highest level of mineralization (2896 ppm), at 70% and 93%, respectively, for green and black teas.

The Bifunctional Catalase-Phenol Oxidase of Mycothermus Thermophilum (MtCATPO) Increases the Antioxidant Capacities of its Ortho-Diphenolic Substrates and of Green and Black Tea Extracts

Catalase from the thermophilic fungus Mycothermus thermophilus is a bifunctional enzyme with a secondary phenol oxidase activity (CATPO). MtCATPO catalyses the oxidation of catechol, chlorogenic acid, caffeic acid and (+)-catechin to yield mainly dimers, and higher molecular weight oligomers and polymers. The role of this phenol oxidase activity is not known. Here, the antioxidant capacities (AC) of the phenolic substrates in the absence and presence of MtCATPO were compared. The oxidized products displayed enhanced AC reaching a maximum of 2.4-fold with catechol. Other phenol oxidases (laccase and tyrosinase) did not yield AC enhancement to the same extent. MtCATPO-treatment increased AC of green and black tea infusions, as well as water extracts of samples collected from a black tea production line up to 28%. The bifunctional MtCATPO appears to be an important antioxidant enzyme with a wide range of potential applications in the food, neutraceuticals and pharmaceuticals industry.

Comparative effects of extracted polyphenols from black and green tea wastes on in-vitro fermentability of feed ingredients

The effect of using black and green tea waste extracts on the diet nutritional value was investigated with three methods of in vitro degradability, gas production, and McNiven’s enzymatic digestion in the present experiment. Total phenolic compounds and total tannin for green tea extract were 20.3% and 14.8% of dry matter (DM), respectively, and for black tea were 18.7% and 12.7% of dry matter, respectively. The addition of green and black tea waste extracts reduced both gas production during incubation hours and dry matter degradability (DMD) in the diet (p < 0.05). A significantly reduced ruminal dry matter disappearance (p < 0.05) and a significantly increased post-ruminal dry matter disappearance (p < 0.05) were observed by adding black and green tea waste extracts. According to the results, the dry matter disappearance throughout the gastrointestinal tract was not significantly different between treatments. It can generally be concluded that the addition of phenolic compounds can be used depending on the nutritional strategy, such as reducing ruminal degradability and increasing rumen nutrient escape.

Kombuchas from green and black teas reduce oxidative stress, liver steatosis and inflammation, and improve glucose metabolism in Wistar rats fed a high-fat high-fructose diet

The aim of this study was to evaluate the effect of green and black tea kombuchas consumption on adiposity, lipid metabolism, liver steatosis, oxidative stress, and inflammation in Wistar rats...

Health Benefits of Aqueous Extract of Black and Green Tea Leaves

Tea, next to water, is the beverage humans consume. Drinking the beverage tea is great for joining and collecting family members and public communities since ancient times. Tea plant Camellia sinensis has been cultivated for thousands of years, and its leaves have been used for medicinal purposes. Various studies suggest that polyphenolic compounds present in green and black tea are associated with beneficial effects in prevention of cardiovascular diseases, particularly of atherosclerosis and coronary heart disease. Anti-ageing, antidiabetic and many other health beneficial effects associated with tea consumption are described. Evidence is accumulating that catechins and theaflavins, which are the main polyphenolic compounds of green and black tea, respectively, are responsible for most of the physiological effects of tea. This review describes the evidence from clinical and epidemiological studies in the prevention of chronic diseases like cancer and cardiovascular diseases and inhibits pathogenic bacteria and general health promotion associated with tea consumption.