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Tea is a beverage widely taken across the world. Tea is a polyphenol-rich beverage made from the leaves of the Camellia sinensis plant, important polyphenols include flavonoids and catechins (Reygaert, 2017).
Polyphenols are a class of naturally occurring phytochemicals found in high concentrations in plant-based diets (Vauzour, 2012).
The most prevalent polyphenol in tea is Epigallocatechin-3-gallate, which is principally responsible for tea’s health benefits (Reygaert, 2017).
Antioxidants are compounds that prevent free radicals from forming (Kinnula and Crapo, 2004). Antioxidants can be in their natural form or in synthetic form (Crapo, 2004). Many researchers have been concerned about synthetic antioxidants because of their negative side effects (Atiqur et al.,2008).
The current trend in drug discovery is to search for natural antioxidants for the prevention and treatment of diseases arising from oxidative stress (Ashokkumar et al., 2008; Veerapur et al., 2009).
In the year 2002, a report from WHO showed that there are at least 2.7 million deaths worldwide each year due to a lack of fruit and vegetable consumption. (Surh, 2003).
Green tea is made up of different components which include: Amino-acids, Organic acids, vitamins, catechins, minerals, flavonols, depsides, methylxanthines (Rady et al., 2018).
The amino-acids present in green tea includes Gamma-aminobutyric acid, Theanine (Rady et al., 2018). The Gamma-aminobutyric acid found in green tea has been known to reduce blood pressure or hypertension. Research carried out in Japan showed that Theanine present in green tea help balances blood pressure, through the proper functioning of the heart and circulatory system.
Organic acids present in green tea include Folic acid, Ascorbic acid, Gallic acid and Quinic acid (Rady et al., 2018). The Ascorbic acid and Gallic acid present in green tea are antioxidants that help fight against harmful oxidation in the body. Folic acid present in tea helps in the formation of blood cells and also in the increase of blood cells. Quinic acid in green tea serves as an astringent, it gives green tea its bitter taste.
Vitamin B2, Vitamin B3, Vitamin B6, and Vitamin E are all present in green tea. Vitamin B2 also known as Riboflavin, helps in the breaking down of carbohydrates, proteins and fats, also in the conversion of carbohydrates to Adenosine Triphosphate (ATP). Vitamin B3 which is also known as Niacin helps in releasing energy from foods taken into the body. Vitamin B6 also known as pyridoxine, helps in relieving stress by releasing the hormone serotonin, no wonder people take tea during stressful moments. Tocopherol, generally known as vitamin E, is an antioxidant.
Epicatechin, Epigallocatechin, Epigallocatechin-3-gallate, and Epicatechin-3-gallate are all catechins found in green tea. Epicatechin and Epicatechin-3-gallate in tea plays a role in reducing blood glucose level in people suffering from diabetics, it also has an anti-cancer effect. Epigallocatechin and Epigallocatechin-3-gallate play a role by helping to reduce inflammation, loss of weight and also in the prevention of some chronic diseases.
Zinc, Manganese, Phosphorus, Selenium, Potassium, and Sodium are minerals found in green tea. Zinc found in tea helps in boosting the immune system and also helps in the growth and development of children, no wonder it is recommended also for children. Manganese in tea helps in the activation of useful enzymes in the body by acting as a co-factor. Green tea contains phosphorus, which aids in the production of flavonoids, as well as polyphenols, amino acids, and caffeine. Selenium is a trace mineral and serves as an antioxidant, it also improves the immune system. Potassium and Sodium found in teas help to maintain or balance normal levels of fluids in the cells
Quercetin, Myricetin, and Kaempferol are some of the flavonols found in green tea. Tea contains the antioxidants quercetin and kaempferol, which have been linked to a lower risk of cardiovascular disease. Tea contains myricetin, which has anti-oxidant, anti-inflammatory, and anti-cancer properties (Jeganathan et al., 2016)
Theobromine, Caffeine, and Theophylline are among the methylxanthines found in green tea. Tea contains theobromine and theophylline, which are bronchodilators and vasodilators, they also help in relaxing muscles, they are important in the treatment and prevention of shortness of breath in asthmatic patients and people suffering from different respiratory disorders (Bispo et al., 2002). Caffeine in tea serves majorly to stimulate the brain and central nervous system, it is the reason for activeness and alertness after taking a cup of tea.
Theogallin, Chlorogenic acid, and Coumarylquinic acid are some of the depsides found in green tea. Chlorogenic acid has been known to play a role in glucose regulation and help prevent the development of type 2 diabetes (Jasmine et al., 2015). Theogallin in tea serves as an anti-depressant and also helps in cognitive abilities.
Another component present in tea are the volatile compounds, they are gases or chemicals that evaporate or vapourises mostly when heated, this vapour can be inhaled, it is the reason why we perceive the sweet aroma from hot tea, these components present in tea are what forms vapour when green tea is heated and we inhale. These components include indole, geraniol, nerolidol, linalool etc.
Green tea has numerous health benefits, including anti-carcinogenic, anti-inflammatory, anti-microbial, anti-oxidant, cardio-protective, and oral health (Reygaert, 2017).
One important property of green tea is chemoprevention. Chemoprevention is the use of agents to prevent, reverse, or slow tumour growth. Phytochemicals derived from edible plants have been shown to disrupt a specific stage of the carcinogenic process (Surh, 2003).
Chemoprevention with naturally occurring phytochemicals is an excellent cancer therapy strategy (Siddiqui, 2010).
Cancer is a term used to describe a group of diseases characterized by abnormal cell proliferation that has the potential to spread to other parts of the body (Kohler, 2015). Following cardiovascular disorders, it is the second most common cause of death (Ma and Yu, 2014).
Tea’s epigallocatechin-3-gallate components aid in the induction of apoptosis while also providing chemopreventive effects. Apoptosis refers to programming cells to death, cells that are old and worn out are usually programmed to death in other for them not to form harmful cells to the body, likewise, cells that are mutated are also programmed to cell death because these cells can turn to cancerous cells (Bostan, 2016).
Epigallocatechin-3-gallate also helps in modulating cell proliferation, cell proliferation not regulated or modulated can lead to the generation of cancerous cells. By causing cell cycle arrest, epigallocatechin-3-gallate can control cell growth (Feitelson, 2015).
To summarize, tea is a pleasant, popular, socially acceptable, cost-effective, and safe beverage with no negative side effects. It is now proven as having the future potential of becoming an important industrial and pharmaceutical raw material.
Daily intake of 2-3 cups of tea is recommended.
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