Green tea polyphenols prevent Parkinson's disease

Green tea is a beverage consumed around the world that is believed to have substantial health benefits such as reducing the risk of cancer, cardiovascular diseases, diabetes and neurodegeneration. This beverage is prepared from the leaves (steamed and dried) of the Camellia sinensis plant and contains strong antioxidant and neuroprotective phenolic compounds from which the most important is (-)-Epigallocatechin-3-gallate. 

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders, characterized by bradykinesia, rigidity with cogwheeling, rest tremor, and postural instability. The clinical manifestations of this pathology include a broad spectrum of symptoms of psychomotor impairment such as gait disturbance, slowness, tremors, and an increased propensity to falling. The prevalence of Parkinson's disease worldwide is known to range from 0.5 percent to 4 percent among the elderly aged 65 years or older.

Oxidative stress is implicated in PD and it has been found that polyphenols present in green tea catechins have the ability to modulate cell health status by inducing detoxification in response to free radical stress.

Green tea contains polyphenols, which have been found to block the backflow of dopamine and allow it to travel from one area of the brain to another. Therefore, green tea can help to ease movements and prevent the tremors associated with Parkinson's.

Catechin polyphenols can act as antioxidants by scavenging free radicals and chelating excess metal ions. They may also indirectly reduce oxidative stress, inhibiting redox-sensitive transcription factors, nuclear factor-κB, and pro-oxidant enzymes, such as inducible nitric oxide synthase, and inducing phase II antioxidant enzymes, such as glutathione S-transferases and SOD.

(-)-Epigallocatechin-3-Gallate (EGCG) is the most abundant polyphenol in green tea that can bind iron. It has been shown to have antioxidant effects in vitro by trapping peroxyl radicals, inhibiting lipid peroxidation, and contributing to the neuroprotective effect in several PD cell models.
Green tea polyphenols prevent Parkinson's disease

Chemical constituents of green tea

Green tea is produced without fermentation and undergoes minimal oxidation possible during processing. Green tea can be the raw material for extracts which are used in different beverages, dietary supplements and also in cosmetic items.

Most of the beneficial effects of green tea are attributed to its polyphenolic flavonoids, known as catechins the major flavonoid. These polyphenols account for up to 40% of the dry weight of green tea.

The chemical composition of green tea varies with genetic strain, climatic conditions, soil properties, plucking season, position of the leaf, processing and storage.

Chemical composition is complex consisting of proteins (15–20% dry weight) whose enzymes constitute an important fraction; amino acids (1–4% dry weight) such as teanine or 5-N-ethylglutamine, glutamic acid, tryptophan, glycine, serine, aspartic acid, tyrosine, valine, leucine, threonine, arginine, lysine; carbohydrates (5–7% dry weight) such as cellulose, pectins, glucose, fructose, sucrose; lipids as linoleic and a-linolenic acids; sterols as stigmasterol; vitamins (B, C, E); xanthine bases such as caffeine and theophylline; pigments as chlorophyll and carotenoids; volatile compounds such as aldehydes, alcohols, esters, lactones, hydrocarbons, etc.; minerals and trace elements (5% dry weight) such as Ca, Mg, Cr, Mn, Fe, Cu, Zn, Mo, Se, Na, P, Co, Sr, Ni, K, F, and Al.

Caffeine is mainly a trimethyl derivative of purine 2, 6-diol and is produced from leaves of the tea plant from the ancient time. Coffee beans contain about 1.5 % caffeine, while caffeine content of green tea is up to 5%. It functions as a cardiac and also as a diuretic. It can also stimulate the cerebral cortex which results in central nervous system excitation.

Carbohydrate is the major constituent of tea leaf that includes cellulosic fibre and the next is protein, but these components are not soluble.

Generally, the major catechins of tea leaves are (+)-catechin (C), (−)-epicatechin (EC), (+)-gallocatechin (GC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin gallate (EGCG), and (+)-gallocatechin gallate (GCG).

The antioxidant properties of catechins are mainly related to the number and position of hydroxyl group in the molecules and consequently binding and neutralization of free radicals by these hydroxyl groups. Previous studied have shown that tea catechins are excellent electron donors and effective scavengers of physiologically relevant reactive oxygen species in vitro, including superoxide anions.

Among total nitrogen found in the green tea infusion, one fifth of them originate from caffeine and related compounds. Other forms of nitrogenous compounds found in tea infusion are amino acids, amides, certain proteins, and nucleic acids.
Chemical constituents of green tea

Antioxidant in green tea

Green tea is made from leaves of camellia sinensis that have undergone minimal oxidation during processing. The chemical composition of green tea varies with genetic strain, climatic conditions, soil properties, plucking season, position of the leaf, processing and storage.

The chemical composition of tea leaves has been well documented. The main constituents of tea leaves are polyphenols. Polyphenols constitute the most interesting group of green tea leaf components and in consequence green tea can be considered as an important dietary source of polyphenols, particularly flavanoids. Especially, catechins, the main component of polyphenols, are well known for their antioxidant properties, which have led to their evaluation in many diseases associated with free radicals, including cancer, cardiovascular and neurodegenerative diseases.

Generally, the major catechins of tea leaves are (+)-catechin (C), (−)-epicatechin (EC), (+)-gallocatechin (GC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECg), (−)-epigallocatechin gallate (EGCg), and (+)-gallocatechin gallate (GCg).

The antioxidant activity of green tea polyphenols is primarily attributed to the combination of aromatic rings and hydroxyl groups that assemble their chemical structure and consequently binding and neutralization of lipid free radicals by these hydroxyl groups. Catechins also exhibit antioxidant activity via chelating redox active transition-metal ions. Polyphenolic compounds, possess hydroxyl and carboxyl groups, are able to bind particularly iron and copper.

A wide variety of other components exists, including, flavones, phenolic acids and depsides, carbohydrates, alkaloids, minerals, vitamins and enzymes. Green tea also contains carotenoids, tocopherols, ascorbic acid (vitamin C), minerals such as Cr, Mn, Se or Zn, and certain phytochemical compounds.
Antioxidant in green tea