Green tea extract
Encyclopedia
A green tea extract is a herbal derivative from green tea leaves (Camellia sinensis
). Containing antioxidant
ingredients – mainly green tea catechins (GTC) – green tea and its derivatives are sought-after amongst people who pursue health.
Soft extracts
Dry extracts
Partly purified extracts
They can also be called green tea polyphenols (GTP or GTPs). The category includes epigallocatechin gallate
(EGCG), epigallocatechin (EGC), epicatechin gallate
(ECG) and epicatechin (EC). Of which, EGCG accounts for more than 40% of the total content.
(ECG), and epigallocatechin gallate
(EGCG).
Other components include three kinds of flavonoid
s, known as kaempferol
, quercetin
, and myricetin
. A remarkably higher content of myricetin is detected in tea and its extracts than in many other plants, and this high concentration of myricetin may have some implications with the bioactivity of tea and its extracts.
Caffeine
may be excluded in green tea extracts in order to avoid side-effects; caffeine-free green tea extract supplements are now available.
. The main attribution is supposed to be EGCG.
In alkaline solutions (pH > 8) GTC (green tea catechins) is rather unstable; in acidic solutions (pH < 4), however, GTC shows excellent stability. The stability in alkaline solutions varies between four components of GTC in green tea extracts. Recent study demonstrates that EGCG and EGC is more unstable than EC and ECG in a basic solution, giving an explanation to the fact that EGCG and EGC do not circulate in the basic sodium phosphate buffer fluid of human body.
In a high temperature environment, GTC is not stable: an epimerization change is likely to occur, because heating results in the conversion from EGCG to GCG. Thus it is considered inappropriate to infuse green tea or its extracts with overheated water.
, anticarcinogen
, anti-inflammatory
, and anti-radiation.
Green tea extracts exhibit stronger antioxidant protection for human body than vitamin C
and vitamin E
. Scavenging effect of lipid free-radicals (one antioxidant property) of polyphenols in green tea extracts can be clearly observed in experiments. The ability of GTP in green tea extracts to eliminate lipid-derived free radicals is noticeably stronger (almost 50 times) than that of ginkgo biloba extracts. Further investigations indicate that the boosting level of superoxide dismutase
(SOD) and glutathione dismutase (GSHPx) may account for the inhibitory effect of GTC against lipid oxidation (rancidification
). It should be mentioned that from the antioxidant perspective, green tea extracts are, generally speaking, more effective than black tea extracts due to the better preservation of catechins.
Moreover, the anticarcinogenic property make the green tea extracts a hotspot in recent scientific researches. In many experiments, green tea extracts show inhibitory effects on cancer cells. In vitro assays, Catechin and caffeine, which are main components in green tea extracts, block the cell cycle of cancer cells (cytotoxicity
) and induce programmed cell death; in vivo, green tea extracts also inhibits prostatic carcinoma transplanted in nude mice.
In addition, green tea extracts also contain a wide-ranged anti-inflammatory characteristics, so it may be helpful in treating chronic inflammatory states. The bactericidal activity against S.mutans is conspicuous in Japanese green tea extracts, and the maltose
level in mouth is consistently lower after drinking tea. Therefore, green tea extracts may be effective in oral hygiene maintenance.
Green tea extracts show anti-radiation properties on white rats in radioactive isotope experiments.
For a green tea extract standardized for 80 percent polyphenols and 55 percent EGCG, a daily dose of 300 to 400 mg green tea extracts is recommended. Some green tea extracts may have as little as 15 percent polyphenols, usually these are far less expensive. It should be kept in mind that the various components of unpurified green tea extracts have synergistic effects and therefore are better than any individual tea component. Scientists also conclude that tea extracts are better taken between meals in order to avoid decreased iron absorption.
Though green tea extracts show potential anticancer capacity - under some conditions by working together with other drugs and suppressing multidrug resistance in cancer cells - they are not suggested for use alone as a chemotherapy agent for cancer treatment.
Excessive intake of green tea extracts containing caffeine has side effects; an excessive concentration may act as a pro-oxidant to damage DNA
and produce undesirable side effects.
In addition, green tea extracts are a promising solution to prevent apple juice and other foods from microbial contamination. Japanese scientists even have discovered that tea extracts can be developed as dyes that are not susceptible to microbial contamination and possess strong deodorant activity.
is the trademark applied to a series of high grade green tea polyphenol extracts manufactured by the Mitsui Norin Co., Ltd. of Japan.
Camellia sinensis
Camellia sinensis is the species of plant whose leaves and leaf buds are used to produce Chinese tea. It is of the genus Camellia , a genus of flowering plants in the family Theaceae. White tea, green tea, oolong, pu-erh tea and black tea are all harvested from this species, but are processed...
). Containing antioxidant
Polyphenol antioxidant
A polyphenol antioxidant is a type of antioxidant containing a polyphenolic substructure. Numbering over 4,000 distinct species, many of these compounds have antioxidant activity in vitro but are unlikely to have antioxidant roles in vivo...
ingredients – mainly green tea catechins (GTC) – green tea and its derivatives are sought-after amongst people who pursue health.
Types of green tea extracts
Strong infusions- During the strong infusion green tea leaves are processed by soaking in the aqueous solution of alcohol (the aspect content is about 2% w/w).
Soft extracts
- To obtain soft extracts, the solution made by strong infusion beforehand is further concentrated to 20–25% (the catechin content is about 20% w/w).
Dry extracts
- After the strong infusions have been concentrated to 40–50% solids (the catechin content is above 25% w/w)，they are sprayed and then become dehydrated extract and powder. The leftovers - water content, which is less than 5% w/w, and the extract - are usually processed as a powder containing inert processing aids to become suitable for a variety of uses (tablets, capsules, dry mixes, etc.).
Partly purified extracts
- Further purification processes, for example, solvent extraction or column chromatographyChromatographyChromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
techniques, as well as new techniques such as membrane extraction and separation, are utilized in order to acquire a higher content of tea catechins.
They can also be called green tea polyphenols (GTP or GTPs). The category includes epigallocatechin gallate
Epigallocatechin gallate
Epigallocatechin gallate , also known as epigallocatechin 3-gallate, is the ester of epigallocatechin and gallic acid, and is a type of catechin....
(EGCG), epigallocatechin (EGC), epicatechin gallate
Epicatechin gallate
Epicatechin gallate is a flavan-3-ol, a type of flavonoid, present in green tea. It is also reported in buckwheat and in grape....
(ECG) and epicatechin (EC). Of which, EGCG accounts for more than 40% of the total content.
Constituents
The cardinal antioxidative ingredient in the green tea extract is green tea catechins (GTC), which comprise four major epicatechin derivatives; namely, epicatechin (EC), epigallocatechin (EGC), epicatechin gallateEpicatechin gallate
Epicatechin gallate is a flavan-3-ol, a type of flavonoid, present in green tea. It is also reported in buckwheat and in grape....
(ECG), and epigallocatechin gallate
Epigallocatechin gallate
Epigallocatechin gallate , also known as epigallocatechin 3-gallate, is the ester of epigallocatechin and gallic acid, and is a type of catechin....
(EGCG).
Other components include three kinds of flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
s, known as kaempferol
Kaempferol
Kaempferol is a natural flavonol, a type of flavonoid, that has been isolated from tea, broccoli, Delphinium, Witch-hazel, grapefruit,cabbage, kale, beans, endive, leek, tomato, strawberries, grapes, brussels sprouts, apples and other plant sources. Kaempferol is a yellow crystalline solid with a...
, quercetin
Quercetin
Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...
, and myricetin
Myricetin
Myricetin is a naturally occurring flavonol, a flavonoid found in many grapes, berries, fruits, vegetables, herbs, as well as other plants. Walnuts are a rich dietary source. Trace amounts can be found as glycosides. It is one of the phenolic compounds present in red wine.Myricetin has antioxidant...
. A remarkably higher content of myricetin is detected in tea and its extracts than in many other plants, and this high concentration of myricetin may have some implications with the bioactivity of tea and its extracts.
Caffeine
Caffeine
Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...
may be excluded in green tea extracts in order to avoid side-effects; caffeine-free green tea extract supplements are now available.
Chemical properties
Green tea extract is 20 times more antioxidant-active than Vitamin CVitamin C
Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress...
. The main attribution is supposed to be EGCG.
In alkaline solutions (pH > 8) GTC (green tea catechins) is rather unstable; in acidic solutions (pH < 4), however, GTC shows excellent stability. The stability in alkaline solutions varies between four components of GTC in green tea extracts. Recent study demonstrates that EGCG and EGC is more unstable than EC and ECG in a basic solution, giving an explanation to the fact that EGCG and EGC do not circulate in the basic sodium phosphate buffer fluid of human body.
In a high temperature environment, GTC is not stable: an epimerization change is likely to occur, because heating results in the conversion from EGCG to GCG. Thus it is considered inappropriate to infuse green tea or its extracts with overheated water.
Biochemical properties
The biochemical properties of green tea extracts can be generally divided into four aspects – antioxidantAntioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
, anticarcinogen
Anticarcinogen
An anticarcinogen is any chemical which reduces the occurrence of cancers, reduces the severity of cancers that do occur, or acts against cancers that do occur, based on evidence from in vitro studies, animal models, epidemiological studies and/or clinical studies.Preventative anticarcinogens act...
, anti-inflammatory
Anti-inflammatory
Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....
, and anti-radiation.
Green tea extracts exhibit stronger antioxidant protection for human body than vitamin C
Vitamin C
Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress...
and vitamin E
Vitamin E
Vitamin E is used to refer to a group of fat-soluble compounds that include both tocopherols and tocotrienols. There are many different forms of vitamin E, of which γ-tocopherol is the most common in the North American diet. γ-Tocopherol can be found in corn oil, soybean oil, margarine and dressings...
. Scavenging effect of lipid free-radicals (one antioxidant property) of polyphenols in green tea extracts can be clearly observed in experiments. The ability of GTP in green tea extracts to eliminate lipid-derived free radicals is noticeably stronger (almost 50 times) than that of ginkgo biloba extracts. Further investigations indicate that the boosting level of superoxide dismutase
Superoxide dismutase
Superoxide dismutases are a class of enzymes that catalyze the dismutation of superoxide into oxygen and hydrogen peroxide. As such, they are an important antioxidant defense in nearly all cells exposed to oxygen...
(SOD) and glutathione dismutase (GSHPx) may account for the inhibitory effect of GTC against lipid oxidation (rancidification
Rancidification
Rancidification is the chemical decomposition of fats, oils and other lipids . When these processes occur in food, undesirable odors and flavors can result. In some cases, however, the flavors can be desirable . In processed meats, these flavors are collectively known as "warmed over flavor"...
). It should be mentioned that from the antioxidant perspective, green tea extracts are, generally speaking, more effective than black tea extracts due to the better preservation of catechins.
Moreover, the anticarcinogenic property make the green tea extracts a hotspot in recent scientific researches. In many experiments, green tea extracts show inhibitory effects on cancer cells. In vitro assays, Catechin and caffeine, which are main components in green tea extracts, block the cell cycle of cancer cells (cytotoxicity
Cytotoxicity
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are a chemical substance, an immune cell or some types of venom .-Cell physiology:...
) and induce programmed cell death; in vivo, green tea extracts also inhibits prostatic carcinoma transplanted in nude mice.
In addition, green tea extracts also contain a wide-ranged anti-inflammatory characteristics, so it may be helpful in treating chronic inflammatory states. The bactericidal activity against S.mutans is conspicuous in Japanese green tea extracts, and the maltose
Maltose
Maltose , or malt sugar, is a disaccharide formed from two units of glucose joined with an αbond, formed from a condensation reaction. The isomer "isomaltose" has two glucose molecules linked through an α bond. Maltose is the second member of an important biochemical series of glucose chains....
level in mouth is consistently lower after drinking tea. Therefore, green tea extracts may be effective in oral hygiene maintenance.
Green tea extracts show anti-radiation properties on white rats in radioactive isotope experiments.
Dosage and Side-effects
Green tea extract supplements are accessible over the counter in various forms. Standardized green tea extract is 90 percent total polyphenols, and 1 capsule equals 5 cups of tea.For a green tea extract standardized for 80 percent polyphenols and 55 percent EGCG, a daily dose of 300 to 400 mg green tea extracts is recommended. Some green tea extracts may have as little as 15 percent polyphenols, usually these are far less expensive. It should be kept in mind that the various components of unpurified green tea extracts have synergistic effects and therefore are better than any individual tea component. Scientists also conclude that tea extracts are better taken between meals in order to avoid decreased iron absorption.
Though green tea extracts show potential anticancer capacity - under some conditions by working together with other drugs and suppressing multidrug resistance in cancer cells - they are not suggested for use alone as a chemotherapy agent for cancer treatment.
Excessive intake of green tea extracts containing caffeine has side effects; an excessive concentration may act as a pro-oxidant to damage DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
and produce undesirable side effects.
Food additive and deodorant applications
Because of the high antioxidant activity of green tea extracts, they are hopefully to be used as a kind of innovative food additive to preserve pork, chicken meat, vegetable oil, fish oil and fish flesh, food emulsions and animal fat. This alternative antioxidant is suggested to be a healthier choice; a fairly successful instance may well be the application in Moon cake – the extracts both increase the shelf life and improve the flavor.In addition, green tea extracts are a promising solution to prevent apple juice and other foods from microbial contamination. Japanese scientists even have discovered that tea extracts can be developed as dyes that are not susceptible to microbial contamination and possess strong deodorant activity.
Trademarks
PolyphenonPolyphenon
Polyphenon is the trademark applied to a series of high grade green tea polyphenol extracts manufactured by the Mitsui Norin Co., Ltd. of Japan. The extracts are in part the result of a water based extraction method which begins with green tea leaves, and then involves successive steps which...
is the trademark applied to a series of high grade green tea polyphenol extracts manufactured by the Mitsui Norin Co., Ltd. of Japan.