Chemistry And Applications Of Green Tea Pdf

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Tea Polyphenols Chemistry for Pharmaceutical Applications

Wanda C. Green tea is one of the most popular drinks consumed worldwide. Produced mainly in Asian countries from the leaves of the Camellia sinensis plant, the potential health benefits have been widely studied.

Recently, researchers have studied the ability of green tea to eradicate infectious agents and the ability to actually prevent infections. The important components in green tea that show antimicrobial properties are the catechins. These catechins have been shown to demonstrate a variety of antimicrobial properties, both to organisms affected and in mechanisms used. Infectious diseases are a leading cause of morbidity and mortality worldwide. With the advent of antimicrobial agents in the mids came the hope that eradication of infectious diseases was close.

Unfortunately, the microorganisms involved were able to become resistant to the antimicrobial agents, and that only made it harder to fight these organisms. The CDC has estimated that each year more than two million people in the US suffer from antibiotic-resistant infections and that as many as 23, people die each year from these infections [ 2 ]. This results in not only increased morbidity and mortality, but also increased healthcare costs, which can be a huge financial burden for many countries.

A recent analysis of the medical costs from healthcare-associated infections those infections acquired in a healthcare facility alone estimated that the annual costs of these infections in the US are between 28 and 45 billion dollars [ 3 ].

Antimicrobial resistance issues continue to impact these costs. One study found that the cost of antimicrobial resistance associated illnesses in the US could be as high as 55 billion dollars 20 billion dollars for healthcare costs and 35 billion dollars for lost productivity annually [ 4 ]. To help in the fight against infectious diseases, researchers are looking at the possibilities of using natural plant products, which could turn out to provide a tremendous cost savings in healthcare.

One of the plants that is currently being widely studied is the tea plant, looking especially at green tea. Tea is produced from the Camellia sinensis plant and is grown in over 30 countries.

The best areas for growing tea plants are in specific tropical and subtropical regions. There are four main tea types produced: white, green, Oolong, and black tea. The type of tea is determined by how the tea leaves are processed, specifically by drying and fermentation methods. White tea is processed the least and uses very young leaves and leaf buds. Green tea is produced from more mature leaves with no fermentation. Oolong tea is produced by partially fermenting the leaves and black tea by fully fermenting the leaves [ 5 — 7 ].

Green tea is most commonly consumed in China, Japan, and Korea. Black tea is most commonly consumed in the US and the UK [ 8 ]. Green tea has been shown to have anticarcinogenic, anti-inflammatory, antimicrobial, and antioxidant properties and is beneficial in cardiovascular disease CVD , diabetes and obesity, and neurologic and oral health. The anticarcinogenic properties include controlling cell proliferation, apoptosis and angiogenesis in tumor cells [ 9 — 12 ].

Inflammation is a component of many conditions and diseases including aging, arthritis, cancer, CVD, diabetes, and obesity. The general anti-inflammatory properties of green tea include the ability to decrease the denaturation of proteins and increase the production of anti-inflammatory cytokines [ 7 , 13 ].

Oxidative stress results from the damaging effects of reactive oxygen species ROS. The antioxidant properties of green tea include the ability to limit the amount of free radicals by binding to ROS, upregulating basal levels of antioxidant enzymes, and increasing the activity of these antioxidant enzymes [ 6 , 14 , 15 ]. The effects of green tea on CVD include the anti-inflammatory and antioxidant effects.

In addition, the consumption of green tea has been shown to inhibit atherosclerosis, reduce total lipid levels, and improve the ratio of LDL to HDL [ 16 , 17 ]. Diabetes and obesity are closely associated with a spectrum of disorders known as metabolic syndrome MetS which includes increased waist diameter, elevated plasma triglycerides, decreased HDL, increased fasting blood glucose, and elevated blood pressure [ 18 , 19 ].

Type 2 diabetes is also associated with insulin resistance and sometimes decreased insulin production. Green tea has been shown to increase insulin receptor sensitivity and stimulate glucose-induced insulin secretion [ 20 , 21 ].

Obesity is a result of an increase in fat mass which is caused by increase in the size of fat cells. Green tea has been shown to inhibit digestive enzymes and absorption of fat, which leads to decreased body waist circumference, intra-abdominal fat, plasma total and LDL cholesterol, triglycerides, and blood pressure [ 22 — 24 ].

The challenges of inflammation and oxidative stress can lead to DNA damage, protein misfolding, and loss of ATP production in mitochondria. This can result in cell death and loss of cognitive functions in the brain. The anti-inflammatory and antioxidant properties of green tea also protect neurons, and green tea metabolites have been shown to cross the blood brain barrier [ 25 — 29 ].

Green tea has been shown to be antimicrobial against most oral bacteria. In addition, it has been shown to improve oral health by increasing the activity of oral peroxidases, preventing the development and progression of periodontitis, and reducing dentin erosion and tooth loss, and it has a role in improving bad breath [ 30 — 34 ].

The components in green tea that are the most medically relevant are the polyphenols. The most pertinent polyphenols are the flavonoids; and the most pertinent flavonoids are the catechins. Green tea contains more catechins than the other teas, mainly because of the way it is processed after harvesting.

The amount of catechins in green tea can also be affected by where the tea is grown, the growth conditions, when it is harvested, how the leaves are processed, and the brewing temperature and length of time of brewing. These factors lead to a huge variation in catechin content among the varieties and brands of green tea consumed [ 35 — 45 ]. As mentioned above, there can be a wide variation in the amount of catechins in any particular green tea beverage, although standardized extracts are available for use as supplements [ 7 , 46 , 47 ].

In order to be effective in the body these catechins need to be bioavailable after consumption. Once in the body, the catechins undergo metabolic processing in the liver and small intestine and colon.

This processing produces glucuronide and sulfate conjugates or methyl epicatechins. Catechins are generally most stable in solution at a pH range of It is now known that human serum albumin acts as a stabilizer, binding to the catechins and then transporting them [ 50 ]. Various studies in humans have found that the peak concentrations of catechins and their metabolites occur in blood plasma between 1. Commonly, the levels found in the body are directly proportional to the amount of catechins consumed [ 51 — 53 ].

Tables 1 and 2 show examples of blood plasma and urine concentration studies in humans. The antimicrobial effects of green tea catechins GTCs on microorganisms have been studied for many years.

Green tea has been shown to combat these organisms in various ways, directly and indirectly, and has been shown to work synergistically with some antibiotic agents.

Other known health benefits of green tea such as the anti-inflammatory and antioxidant effects may also contribute to the antimicrobial effects. Studies conducted on Escherichia coli found that exposure to green tea polyphenols GTPs resulted in major gene expression changes for 17 genes, with upregulation occurring in nine genes and downregulation in eight genes [ 75 — 77 ].

Table 3 shows a summary of the antimicrobial effects of green tea on bacteria. One of the major properties of GTCs is the ability to bind to bacterial cell membranes. This binding can lead to interference in various bacterial processes and can damage the cell membrane resulting in increased permeability and leading to cell lysis.

Because EGCG is negatively charged it can combine with the positively charged bacterial cell membrane, especially in gram positive bacteria. The lipopolysaccharide LPS on the outer membrane of gram negative bacteria makes them more resistant to binding by GTCs [ 53 , 63 , 64 , 66 ]. Studies with E. Studies with Staphylococcus aureus have shown that this assault on the cell membrane causes a major cell wall stress response, resulting in upregulation of peptidoglycan biosynthesis genes and an alteration in cell wall structure.

An important result of green tea binding is the loss of bacterial ability to bind to host cells. Studies using human and mammalian cells lines have shown that various bacteria such as Fusobacterium nucleatum , Staphylococcus epidermidis , and Helicobacter pylori have significantly decreased adherence to these cells [ 66 , 67 , 80 ]. Other important results are the loss of the ability for quorum sensing and biofilm formation of P.

Damage to the cell membrane also results in loss of function to transmembrane transporter proteins which are responsible for secretion of toxins and efflux of substances such as antimicrobial agents [ 53 , 65 , 69 , 70 ].

There are a wide variety of other effects that GTCs have on bacterial functions. An important one which can affect most bacteria is the ability of GTCs to inhibit bacterial fatty acid biosynthesis by inhibiting enzymes involved in the biosynthetic pathway. Because this is an essential pathway for most bacteria, researchers are looking at targeting this pathway in antimicrobial drug development.

Fatty acids are important for building cell membranes, as an energy source, and are involved in the production of toxic bacterial metabolites [ 53 , 73 ]. Another target is the folate biosynthesis pathway. The enzyme dihydrofolate reductase DHFR is essential in this pathway, and is known to be a target for certain sulfa drugs.

Other important effects against enzymes include inhibition of bacterial DNA gyrase, inhibition of bacterial ATP synthase activity, and inhibition of bacterial protein tyrosine phosphatase and cysteine proteases [ 53 , 71 , 83 ].

Some specific bacterial effects include reducing bacterial H 2 S production and inhibiting hemolytic activity of F. Since GTCs are known to have antimicrobial action, researchers have begun assessing the potential synergism of these catechins with other known antimicrobial agents.

Green tea catechins have now been shown to act in synergy with imipenem against MRSA; with metronidazole against Porphyromonas gingivalis ; with azithromycin, cefepime, ciprofloxacin, chloramphenicol, doxycycline, erythromycin, nalidixic acid, piperacillin, or tobramycin against E. The ability of GTCs to inhibit the function of bacterial efflux pumps as mentioned previously also plays a role in at least an additive antimicrobial effect for GTCs and many antimicrobial drugs, especially in gram negative bacteria that possess RND-type efflux pumps [ 53 , 69 , 70 , 85 — 89 ].

Table 4 lists antimicrobial agents that have shown synergy with GTCs and the targets of these drugs. Green tea catechins have also been shown to be effective against a number of viruses, parasites, fungi, and even prions.

Studies performed with adult healthcare workers to determine if green tea supplements could prevent infection with viruses causing influenza showed significantly fewer instances of influenza symptoms and a reduced incidence of laboratory-confirmed influenza cases versus the control group [ 97 ]. The main effect of GTCs on various parasite infections is a decrease in parasite numbers and growth.

Other effects noted were fragmentation of parasite DNA and reduced fatty acid synthesis in the parasites. Studies with parasites include Plasmodium falciparum , Babesia spp. Research testing for synergistic effects found that EGCG showed synergism with amphotericin B, fluconazole, and miconazole in Candida spp. In the abnormal shape, protein function is lost and protein aggregation occurs in cells.

Unlike other infectious agents, prions cannot be destroyed using autoclaving; the proteins have to be degraded to be noninfectious. There is a large amount of research that has assessed the antimicrobial effects of green tea catechins on a wide variety of microorganisms, including many gram negative and gram positive bacteria, some viruses, fungi, and prions.

One of the most clinically important bacteria that has been researched is S. The most studied gram negative bacteria is E. There are several recently published manuscripts that contain extensive information on which organisms are affected by green tea catechins [ 53 , 64 , 96 , ]. Since it has been shown that GTCs have multiple types of antimicrobial abilities against so many organisms, it would be expected that green tea catechins could also prevent infections.

One study was mentioned previously describing how green tea reduced the number of colds and influenza incidents. A study involving children found that, in school-aged children who consumed green tea on a regular basis, the number of incidents of influenza A or B was inversely associated with the number of cups of green tea consumed per day or per week [ ].

Activity of catechins and their applications

Metrics details. Catechins, which are polyphenol compounds found in many plants and are an important component of tea leaves, are strong anti-oxidants. Many studies seek to enhance the effects of catechins on the human body and boost their protective power against UV radiation. There are many examples of the positive anti-microbial, anti-viral, anti-inflammatory, anti-allergenic, and anti-cancer effects of catechins. Catechins increase the penetration and absorption of healthy functional foods and bio cosmetics into the body and the skin, thus improving their utility. High value-added anti-oxidant substances have been extracted from food and plant sludge, and experiments have shown that catechins are safe when applied to the human body. The stability of catechins is very important for their absorption into the human body and the effectiveness of their anti-oxidant properties.


This review outlines the chemistry, flavour components, antioxidant mechanism, regulatory status, food applications, and stability of green tea extract in food.


Bactericidal activity of green tea extracts: the importance of catechin containing nano particles

Tea is an aromatic beverage commonly prepared by pouring hot or boiling water over cured or fresh leaves of Camellia sinensis , an evergreen shrub native to East Asia. Tea has a stimulating effect in humans primarily due to its caffeine content. The tea plant originated in the region encompassing today's Northeast India , north Myanmar , Southwest China and Tibet , where it was used as a medicinal drink by various ethnic groups. Portuguese priests and merchants introduced it to Europe during the 16th century. The term herbal tea refers to drinks not made from Camellia sinensis : infusions of fruit, leaves, or other plant parts , such as steeps of rosehip , chamomile , or rooibos.

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Wanda C. Green tea is one of the most popular drinks consumed worldwide. Produced mainly in Asian countries from the leaves of the Camellia sinensis plant, the potential health benefits have been widely studied.

Tea is an aromatic beverage commonly prepared by pouring hot or boiling water over cured or fresh leaves of Camellia sinensis , an evergreen shrub native to East Asia. Tea has a stimulating effect in humans primarily due to its caffeine content. The tea plant originated in the region encompassing today's Northeast India , north Myanmar , Southwest China and Tibet , where it was used as a medicinal drink by various ethnic groups.

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This monograph is intended to serve as a guide to industry for the preparation of Product Licence Applications PLAs and labels for natural health product market authorization. It is not intended to be a comprehensive review of the medicinal ingredient. This monograph excludes foods or food-like dosage forms as indicated in the Compendium of Monographs Guidance Document. Acceptable dosage forms for the age category listed in this monograph and specified route of administration are indicated in the Compendium of Monographs Guidance Document. To be used with a program of reduced intake of dietary calories and increased physical activity if possible to help in weight management Nagao et al.

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