Rezumat al activității antioxidante a ceaiului
The Summary of Antioxidant Activity of Tea
The content of tea contains water content(75%) and dry weight matter(25%); Dry weight matter contains inorganic chemicals (3.5%-7%) and organic chemicals(93%-96%); Inorganic chemicals contains water-soluble chemicals (2%-4%) and water-insoluble chemicals(1.5%-3%); Organic chemicals contains N compounds{amino acid(1-7%),Protein(20-30%), alkaloid(2-5%), Enzyme} and C compounds{tea polyphenol(20-35%), (aromatic matte (0.02%), ester(8%), Organic acids(3%),pigments(1%),vitamin(0.6-1%)}.
In tea leaves, catechin content is 12% to 24% of dry weight matter, the content of catechin in tea polyphenols count up to about 70% of the total, of which epigallocatechin (EGC), epigallocatechin gallate EGCG, and count up to about 50% of the total catechins.
Tea Polyphenols (TP), also known as tea tannin, is a generic term of phenolic compounds in tea, including Flavanoids ( catechins ) , anthocyanins ( anthocyanins and Leucoanthocyanidin ). Flavonoides, flavonols , phenolic acids and Depsides etc matters. It is one of the important components that form the quality of tea, and it is the most important, the most essential and the most beneficial component to the human body extracted from tea. Its main component is flavan-3-ol derivatives, commonly known as catechins. Except for phenols and condensed phenols, their structures all have a C6-C3-C6 basic carbon skeleton with a-phenylbenzodihydropyran (flavan) as the main body.According to the chemical structure can be divided into four categories: epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin(EC) , more stable at pH 4-8, acid, alkali , light, heat , transition metals prone to deterioration polyphenols .
Type | TP40 | TP50 | TP80 | TP90 | TP95 | TP98/1 | TP98/2 |
|---|---|---|---|---|---|---|---|
Tea Polyphenols | 40 | 50 | 80 | 90 | 95 | 98 | 98 |
Catechins | 25 | 30 | 60 | 70 | 75 | 80 | 80 |
Caffeine | 10 | 10 | 10 | 8 | 5 | 5 | 0.5 |
EGCG | 30 | 30 | 40 | 40 | 45 | 45 | 50 |
The antioxidant activity of tea polyphenols are 4-6 times of butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), is 6-7 times of VE, 5-10 times of VC, and without the potential side effects like compounds.
The antioxidants in tea are mainly epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin(EC), caffeine , carotenoids, vitamin E, vitamin C, gallic acid and chlorogenic acid.
Catechins, including non-esterified catechins and esterified catechins. Non-esterified catechins known as (+)-catechin (DL-C), (-)-epicatechin (L-EC), (+)Gallocatechin (DL-GC), and (-)Epigallocatechin gallate (L-EGC). Esterified catechins known as (-)epicatechin gallate (L-ECG), and (-)epigallocatechin-3-gallate (L-EGCG). The maximum content of catechin in tea is EGCG, second is ECG and EGC is next.
According to research, the four kinds of catechins with strong antioxidant capacity are in the order of EGCG>EGC>ECG>EC according to the equimolar concentration, and EGC>EGCG>EC>ECG according to the equimolar concentration. The two components with the strongest oxidizing ability are EGCG and EGC.
The sequence of the ability to remove oxygen free radicals: EGCG>ECG>EC>EGC. The IC50 of EGCG, ECG, EGC and EC to remove lipid free radical is: 0.37, 0.46, 0.27 and 0.30 mmol/L.
According to the determination, in fresh tea leaves, the approximate ratio of these four catechins is EGCG: ECG: EGC: EC=5:2:2:1. Although the proportion of EGCG has an absolute advantage, its synergistic effect is not as good as that of natural combination. This result suggests that when catechin is used as an antioxidant, maintaining the original catechin ratio has the best antioxidant effect.
The chemical composition of tea, coffee, and cocoa as below:
Ingredients | Tea(%) | Coffee(%) | Cocoa(%) |
|---|---|---|---|
Effective Ingredients | Tea Polyphenol:
15-30 | Chlorogenic Acid:
8-10 | Phenols:
10-15 |
Protein | 20-35 | 13-14 | 13-14 |
Crude Fat | 7-12 | 13-15 | 50-55 |
Starch | 0.1-0.3 | 11-12 | 8.8-9.0 |
Reducing Sugar | 1.0-1.4 | 1.0 | 3.1 |
Crude Fiber | 10-25 | 18 | 3-5 |
Ash Content | 5-6 | 3-4 | 2-3 |
Caffeine | 2-4 | 1-2 | 0.4-0.6 |
Theobromine | 0.05 | 0.01 | 1.0-1.5 |
Tea polyphone has synergetic effect with vitamin E at remove water-soluble free radical、remove lipid free radicals on micelles and biological membrane surface and break Free radical chain reaction. The sequence of the reaction rate of vitamin E free radical and tea polyphenol: EGCG>ECG>EGC>EC, and it presents reverse way at its Oxidation potential.
The inhibition effect of tea polyphenol to ONOO—the active oxygen is obviously better than quercetin and vitamins. Pannala’s R1 research discovers ECG and EGCG are better than EC and EGC at the effect of remove peroxynitrite.
Protective effects of tea polyphenols 4 kinds of monomers on iron ion induced brain synaptosomes lipid peroxidation injury in the following order：EGCG>ECG>GTP>EGC>EC．Their ability to remove lipid free radical produced by synaptosomal lipid peroxidation is also a similar order ECG>EGCG>EC>EGC. The Il study of Salah and Rice Evans found tea polyphenols can inhibit LDL peroxidation, the inhibition capacity is similar as above sequence.
Removing effect of tea polyphenols on lipid free radical includes either lipid peroxidation of brain synapses start process induced by iron ions or lipid free radical produced on lipid peroxidation chain reaction. The result also reflects the same mechanism of action on free radicals and tea polyphenols. TBA method is used to measure the inhibition effect of tea polyphenols on lipid peroxidation end product; the result mainly reflects the final results of tea polyphenols as an antioxidant.
Study the protective effect against oxidative damage to DNA about 4 monomers of tea polyphenol by using chemiluminescence technology. Find out that the sequence of protective effect against oxidative damage to DNA is ECG> EC> EGCG> EGC. To determine what kind of free radicals caused DNA damage, We use ESR spin trapping technique to find the sequence of scavenging hydroxyl produced by 4 monomers of tea polyphenols to this system is also ECG> EC> EGCG> EGC, and meanwhile proved the DNA damage caused by the reaction system of (0P) 2Cun, hydrogen peroxide and ascorbic acid is mainly hydroxyl free radical.
The use of EDTA / light riboflavin System 0i found scavenging effect against six kinds of isomers of tea polyphenols enhanced with the following order:EC<(+)-C<EGC<GC<EGCG<GCG, that is the remove effect of three on more than one gallic acid group GCG and EGCG is stronger than GC, EGC, EC and (+)-C, the five on more than one hydroxyl group EGC and GC is stronger than the EC and (+)-C. the remove effect of GCG, GC and (+)-C , respectively better than their isomers EGCG, EGC and EC, and this difference is more pronounced on remove effect at low concentrations.
The pathogenesis of degenerative diseases are related to free radical damage, such as Alzheimer’s and Parkinson’s disease are two typical neurodegenerative disease. Although pathogenesis is multifactorial, but the accumulation of oxidative damage is an important cause of the disease, we have recently found that Tea Polyphenols can prevent apoptosis of PC12 cells induced by 6-OHDA and a preventive role in an animal model of Parkinson’s. The mechanism of tea polyphenols to prevent these diseases is very worthy of further study. Now there are already some studies show that tea polyphenols can enter the bloodstream and can cross the blood-brain barrier. However, these studies require in-depth, such as the concentration of polyphenols into various organs and tissues, morphology and residence time and the mechanism of action of harmful free radicals are required to investigate.
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