The usefulness of a diet rich in vegetables and fruits on human health has been widely recognized: a high intake of antioxidant and bioactive compounds may in fact play a crucial role in the preven...

Strawberry and Human Health: Effects beyond Antioxidant Activity

Effect of Kombucha, a fermented black tea in attenuating oxidative stress mediated tissue damage in alloxan induced diabetic rats

// Xiangbing Mao 1, 2 , Changsong Gu 1, 2 , Daiwen Chen 1, 2 , Bing Yu 1, 2 and Jun He 1, 2 1 Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, 611130, People’s Republic of China 2 Key Laboratory of Animal Disease-Resistance Nutrition, Chinese Ministry of Education, Chengdu, 611130, People’s Republic of China Correspondence to: Xiangbing Mao, email: acatmxb2003@163.com Keywords: oxidative stress, tea polyphenols, antioxidant capacity, pro-oxidant capacity Received: June 20, 2017      Accepted: August 26, 2017      Published: September 14, 2017 ABSTRACT Reactive oxide species are the middle products of normal metabolism, and play a crucial role in cell signaling transduction. On the contrary, accumulation of excess reactive oxide species results in oxidative stress that often brings multifarious impairment to cells, including decrease of ATP level in cells, elevation of cytosolic Ca 2+ , DNA damage, dysfunction of biological function in lipid bilayer and so on. These effects will finally lead to all kinds of diseases. Tea polyphenols are widely considered as a kind of excellent antioxidant agents. It can be antioxidants by directly scavenging reactive oxide species or chelating transition metals, and indirectly upregulating the activity of antioxidant enzymes. In addition, tea polyphenols have also been observed a potent pro-oxidant capacity, which directly leads to the generation of reactive oxide species, and indirectly induces apoptosis and death of cancer cells. The underlying characters of its pro-oxidant activity in some diseases is not well understood. The present review we will discuss the dual character of tea polyphenols, both antioxidant and pro-oxidant properties, in some human diseases induced by oxidative stress.

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Oxidative stress-induced diseases and tea polyphenols.

Tea (Camellia sinensis, Theaceae) is a popular beverage consumed worldwide. Green tea, oolong tea, and black tea are the three major tea types that are obtained through different levels of fermentation of the tea leaves. The health benefits of tea have been widely studied, and these effects are closely related to the structure and composition of polyphenols. In spite of growing evidences for health benefits of green tea, less research has been done using black and oolong teas, which are more widely consumed. This mini-review mainly focused on biological activities of oolong and black tea, and their characteristic polyphenols, i.e., oolong tea theasinensins, and black tea theaflavins. Several biological activities have been associated with tea consumption and polyphenol contents, including anticancer activities, antioxidant activities, anti-cardiovascular activities, antimicrobial activities, anti-hyperglycemic activities, and anti-obesity activities, suggesting the important roles of tea and tea polyphenols in human health and in disease prevention and treatment. However, application of tea polyphenols in the development of dietary interventions or alternative treatment approaches need to be aware of the low bioavailability and potential toxicity of tea polyphenols. Future studies to incorporate existing methods or develop new methods for enhancing polyphenol absorption will help to obtain these health benefits with a lower dose and prevent overdose toxicity.

The impact of oolong and black tea polyphenols on human health

Numerous epidemiological and interventional clinical studies have consistently reported that black tea is good for human health. The polyphenolic compound, theaflavin, and its galloyl esters (theaflavins) are the primary red pigments in black tea that possess several health benefits, including fat-reducing and glucose-lowering capabilities and lifestyle-related disease prevention related to anti-obesity, anticancer, anti-atherosclerotic, anti-inflammatory, antiviral, antibacterial, anti-osteoporotic, and anti-dental caries properties. These compounds are produced by key enzymes, such as polyphenol oxidase and peroxidase, from parent green tea catechins present in fresh green tea leaves during the production of black tea leaves or the fermentation of green tea. However, theaflavins are only present in low concentrations in black tea; thus, their extraction from black tea leaves at sufficient levels for use in medical studies has been difficult. To circumvent this issue, different procedures for the synthesis of theaflavins using chemical oxidizing reagents or enzymes have been studied; however, low yields have limited their utility. Recently, however, several biosynthetic methods have been developed for the mass production of theaflavins. Using these methods, the physiological functions of theaflavins in lifestyle-related diseases in mice and humans have also been studied. In this review, we present the synthesis of theaflavins and their health benefits.

https://www.mdpi.com/1420-3049/23/4/918/pdf

Synthesis of Theaflavins and Their Functions.

Cancer of the prostate gland is the most common invasive malignancy and the second leading cause of cancer-related death in human males. Many studies have shown that black tea reduces the risk of several types of cancer. We studied the effects of active extracts of black tea and the black tea polyphenols theaflavins (TFs), on the cellular proliferation and mitochondria of the human prostate cancer cell line PC-3. Our studies revealed that Yinghong black tea extracts (YBT), Assam black tea extracts (ABT) and TFs inhibited cell proliferation in a dose-dependent manner. We also showed that TFs, YBT and ABT affected the morphology of PC-3 cells and induced apoptosis or even necrosis in PC-3 cells. In addition, it was observed that the samples significantly caused loss of the mitochondrial membrane potential, release of cytochrome c from the intermembrane space into the cytosol, decrease of the ATP content and activation of caspase-3 compared with the control. Taken together, these findings suggest that black tea could act as an effective anti-proliferative agent in PC-3 cells, and TFs, YBT and ABT induced apoptosis of PC-3 cells through mitochondrial dysfunction.

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Active extracts of black tea (Camellia Sinensis) induce apoptosis of PC-3 prostate cancer cells via mitochondrial dysfunction

In the present study, in vitro free radical scavenging abilities and in vivo antioxidant activities of Assam black tea extract (ASTE) and theaflavins mixture (TFSM) were investigated. Our results showed that ASTE and TFSM had significant free radical scavenging activities in vitroin a dose-dependent manner, especially 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical. For antioxidant activities in vivo, the mice were fed with ASTE and TFSM everyday. The contents of malondialdehyde (MDA), and the activities of superoxide dismutase (SOD) and glutathione per- oxidase (GSH-Px) in the mice serum and liver were measured after 30 days. As a result, TFSM could obviously improve SOD and GSH-Px activities, and reduce MDA content in the serum and liver. Though ASTE also showed a certain antioxidant activity, it was slightly weaker than the antioxidant activity of TFSM in the mice. Moreover, ASTE did not change the activity of GSH-Px in the mice liver. In conclusion, our results showed that black tea and its main polyphenols were effective in scavenging DPPH, ABTS and OH free radicals in vitro, and increasing the SOD and GSH-Px activities, decreasing the MDA contents in the mice. These findings suggest the important significance of black tea consumption in prevention of diseases.

	 

	Key words: Black tea, polyphenols, antioxidant, theaflavin.

Free radical scavenging abilities in vitro and antioxidant activities in vivo of black tea and its main polyphenols

The invention discloses a method for extracting EGCG (epigallocatechin gallate) in tea leaves by water extraction; according to the method, the GCG in the tea leaves is extracted with de-ionized water, and on the basis of a single factor experiment, the extraction condition of the EGCG is optimized by using a response surface method, so as to achieve the optimal extraction condition that the pH (potential of hydrogen) of the de-ionized water is adjusted to be 6, the liquid-material ratio is 41, namely 41ml of de-ionized water is added in per gram of green tea, the mixture is extracted for 34min in a constant-temperature thermostat water bath of 85 DEG C and then is filtered, so as to obtain an EGCG extract, the extraction is repeated for once, and then the EGCG content is detected, wherein the yield of the EGCG can reach 3.40%.

Shunshun Pan

Papers

Active extracts of black tea (Camellia Sinensis) induce apoptosis of PC-3 prostate cancer cells via mitochondrial dysfunction

Free radical scavenging abilities in vitro and antioxidant activities in vivo of black tea and its main polyphenols

Method for extracting EGCG (epigallocatechin gallate) in tea leaves by water extraction