Green Tea: A Potential Alternative Anti-Infectious Agent Catechins and Viral Infections

doi:10.4236/aa.2013.34028

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Advances in Anthropology

2013. Vol.3, No.4, 198-202

Published Online November 2013 in SciRes (http://www.scirp.org/journal/aa) http://dx.doi.org/10.4236/aa.2013.34028

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198

Green Tea: A Potential Alternative Anti-Infectious Agent

Catechins and Viral Infections

Jennifer Tran

University of North Carolina at Chapel Hill, Chapel Hill, USA

Email: [email protected]

Received February 14th, 2013; revised March 17th, 2013; accepted April 13th, 2013

tion License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original

work is properly cited.

Tea is the second most consumed beverage in the world, following water. Black, oolong, and green tea

are products of a perennial tree or shrub called Camellia sinensis. Camellia sinensis is native to Mainland

China and is referenced in Chinese literature at least 5000 years ago. Since its discovery, green tea has

been heralded as having several health benefits associated with its consumption. Traditionally, green tea

has been used for a variety of medicinal purposes, such as the prevention and treatment of a variety of

cancers, mental alertness, weight loss, lowering cholesterol level, and UV protection. Studies have shown

that catechins, the polyphenols found in tealeaves, are effective as anti-infectious agents by affecting the

infection process instead of specifically targeting the virus. This treatment strategy has the potential of

reducing the prevalence of drug-resistant viruses and the reliance on anti-viral drug therapies. This paper

will explore the efficacy of green tea in preventing infections by the hepatitis B and C, influenza and hu-

man immunodeficiency virus.

Keywords: Catechins; Viral Infections; Green Tea; Camellia Sinensis; HIV; Influenza; Hepatitis; Ancient

China; Coevolution; Phytochemicals; Phenols

Introduction

Tea is a widely consumed beverage worldwide. In order for

something to be considered a tea, the beverage must be produc-

ed from the leaves of the evergreen plant, Camellia sinensis,

which is a member of the Thaceae family. Black, oolong, and

green tea are brews of this plant, but vary in their processing

method and degrees of fermentation and oxidation. Steaming

fresh leaves produces green tea, which results in the preserva-

tion of the color (hence the name) and in the highest concentra-

tions of antioxidants in a tea. Studies have shown that the posi-

tive health benefits of green tea may be due to these antioxi-

dants (also known as catechins, the tea polyphenols).

Green tea is widely popular in East Asia (particularly in

China and Japan), whereas, black tea is the preferred tea in the

West. But green tea’s popularity is increasing and is being con-

sumed by more people worldwide due in part to increasing

awareness of the many health benefits that green tea is said to

have as concluded by many scientific studies on this subject

(Random History, 2008).

Ancient China

In Chinese history, the consumption of green tea has been

referenced as far back as the third century B.C. But according

to Chinese folklore, the beginnings of the tea culture began

around 2737 B.C. (Cultural China 2007-2010). The process of

brewing the tealeaves in hot water was discovered accidentally

by the second Emperor of China, Shen Nung. Shen Nung, also

an herbalist who studied plants and herbs, was in the courtyard

of his palace boiling water in order to safely drink it when a

breeze stirred the branches of a tree causing the leaves to drop

into his pot of boiling water. Shen Nung found the combination

to be refreshing and stimulating, and thus the Chinese tea cul-

ture began.

Tea was consumed primarily for its medicinal properties. As

an herbal medicine, Camellia sinensis leaves were added to

food to provide nutrients and also used as an antidote for poison

(Cultural China, 2007-2010). Chinese people prefer to drink tea

after their meals to take advantage of its benefits in aiding di-

gestion. It was also used to increase alertness and alleviate the

effects of depression and nervous conditions (Random History,

2008).

The first written reference to the consumption of tea was in

350 A.D. in a Chinese dictionary (Cultural China, 2007-2010).

During the Tang Dynasty (618-907 A.D.), tea cultivation and

trade increased leading to a period considered the “golden age”

of tea, which is also when tea drinking evolved into an art form

(Cultural China, 2007-2010). In 780 A.D., Lu Yu wrote a book

called Ch’a Ching, or the Tea Classic, that outlined how to

grow and cultivate the plant, how to brew the tea and how to

perform a complicated formal tea ceremony that involved twen-

ty-seven pieces of equipment (Cultural China 2007-2010). The

complexity of the ceremony limited it to wealthy individuals

such as scholars, officials, and members of the royal court. The

manual became the standard for cultivation and production in

China, and eventually became the foundation of a tea ceremony

that emerged in Japan (Moxham, 2003). It was also during the

Tang Dynasty that other flavors, such as jasmine and lotus,

J. TRAN

were being incorporated in the brew (Random History, 2008).

Tea remained costly and was limitedly available to royalty

until the fall of the Mongolian empire in 1368 A.D. (Green Tea

Earth, 2010). As tea cultivation and trade increased, the bever-

age became more available to members of every class. For

example, Chinese seamen drank green tea for its high amount

of vitamin C that warded off scurvy and Buddhists chewed the

leaves to help them with their meditation (Green Tea Earth,

2010). People have found that by drinking tea, their health had

improved, their emotions were soothed, and their perceptions

were heightened (Cultural China, 2007-2010). Tea also became

an economic and political tool utilized by China via trade

throughout mainland Asia (Cultural China, 2007-2010). Com-

pressed tealeaves were used as currency to barter (i.e. for horses)

and kept the Chinese army mobile.

Between 729 and 800 A.D., green tea arrived in Japan

(Green Tea Earth, 2010). Emperor Shōmu, the 45th Emperor of

Japan, gave powdered green tea as gifts to Buddhist monks. In

Japan, the teas Sencha (green tea made from un-ground leaves),

Matcha (green tea made from powder) and Bancha (green tea

made from leaves harvested between summer and autumn)

were first introduced with varying processing levels of the

leaves that had harvested at different times (Green Tea Earth

2010). The tea ceremony became an important practice in Japan

that reflected their desire for peace and harmony.

Because of China’s economic superiority and self-sufficiency,

they were able to limit trade to Canton and prohibit Europeans

from entering and communicating with Chinese merchants

(Cultural China, 2007-2010). Tea was introduced to the West in

1606, with the first shipment to Europe being green tea (Green

Tea Earth, 2010). Tea became popular in Europe and was in

high demand in the eighteenth century, but China was able to

deny them access to the product. In response, Europeans intro-

duced opium to the Chinese resulting in a deficit in China’s

economy in the mid-1800s, forcing the country to open the

country to foreign trade (Cultural China, 2007-2010).

Tea Culture

Food that defines a culture often has enhancement properties.

Green tea is especially popular in East Asia, particularly in

China and Japan. The Chinese have a saying that translates into,

“Firewood, rice, oil, salt, sauce, vinegar and tea are the seven

necessities to begin a day” (Travel China Guide, 1998-2012).

Tea is mentioned because it is an important beverage and a

source of water in Chinese culture. Another phrase used is “Cu

Cha Dan Fan”, which is used to describe a simple meal and

translates to “coarse tea and tasteless dinner.” (Travel China

Guide, 1998-2012) These phrases emphasize the importance

and prevalence of tea in Chinese daily life.

Green tea is not treated simply as something to be consumed

but is also an art form with symbolic references. The tea proc-

ess is well-defined by the Tea Classic, from its cultivation to its

consumption. Tea and tea wares (teapots, teacups, and tea sets)

should match surrounding elements, which underlies the ulti-

mate goal of Chinese culture of harmonious unity of human

beings with nature (Travel China Guide, 1998-2012). Tea also

has been compared to personal characteristics to describe taste

and fragrance, and is a symbol of elegance. Regarded as the

most Zen-like drink, tea has a unifying characteristic that pro-

duces a feeling of calmness and eliminates inequalities between

individuals when sharing a cup of tea (Travel China Guide,

1998-2012). It is described as a beverage of opposites, while

still creating harmonious combinations; it is spiritual and mate-

rial, invigorating and pacifying (Travel China Guide, 1998-

2012).

As other people are introduced to and incorporate green tea

into their lives, a unique tea culture is formed. In Japan, there is

a rigorous tea ceremony called chanoyu which emerged during

the twelfth century that reflects the nation’s character of mak-

ing full use of every resource (Travel China Guide, 1998-2012),

and evolved to become “a precise pattern of behavior designed

to create a quiet interlude during which the hosts and guests

strive for spiritual refreshment and harmony with the universe”

(Pettigrew, 2004). The goal of the tea ceremony is to promote

world peace through a spiritual cultivation that encourages

simplicity and humility (Sen, 1998; Random History, 2008). In

the West, tea may be consumed with sugar and milk and served

with desserts to create a leisurely and romantic atmosphere

(Travel China Guide, 1998-2012).

Although varying tea-drinking habits exist, it is obvious that

tea is enjoyed worldwide and has meaning and value to each

culture despite how long tea has been present in that region.

Green tea is becoming more well known for its medicinal prop-

erties and can be consumed in a variety of ways to take advan-

tage of them, such as, in a beverage, in food products enhanced

with tea catechins, or in concentrated capsules.

Catechins

Phytochemicals are biologically active compounds found in

plants. Catechins are the bioactive compounds found specifi-

cally in the leaves of Camellia sinensis. With increasing speci-

ficity, catechins can be defined as phytochemicals, polyphenols,

flavonoids, and tannins.

Polyphenols describes the chemical compound structure of

having several hydroxyl functional groups (−OH) attached to

an aromatic hydrocarbon group (Xie et al., 2012). Categorized

as secondary metabolites, polyphenols can also be divided into

smaller subgroups. One subgroup of polyphenols is flavonoids,

which has its own subdivision of flavanol monomers (or cate-

chins). Phenols are widely spread throughout the plant kingdom,

which suggests a beneficial adaptation had occurred early in

human and plant history that was naturally selected for. It also

suggests that there exists a long coevolutionary history between

phenolic acids and the consumers of plants that contain them.

Phenols are essential for the fitness of the plants (i.e. growth

and reproduction) and are produced as a defense response against

pathogens. Recent interests in phenolic compounds stem from

their potential protective role against oxidative damage diseases

(coronary heart disease, stroke, and cancers) and its possible

utility as a natural antioxidant.

Catechins are antioxidants that scavenge for free radicals that

can damage DNA, change the cell, cause cell death, and con-

tribute to cancer, blood clots and atherosclerosis (University of

Maryland Medical Center, 2011). These compounds may be

able to do this by neutralizing free radicals and reducing or

even helping prevent some of the damage they cause. Catechins

are more concentrated in green tea due to its minimal process-

ing. They make up approximately 30% to 40% of the dry

weight of green tea leaves (Molinari et al., 2006). Some of the

primary catechin compounds include epicatechin, epigallocate-

chin, epicatechin-3-gallate, and epigallocatechin gallate (EGCG)

(Molinari et al., 2006). Epigallocatechin gallate is the most

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studied and most active catechin in green tea. It makes up ap-

proximately half of the total catechins (University of Maryland

Medical Center, 2011). EGCG is the main active ingredient in

green tea leaves and has a molecular formula of C22H18O11

(Umashankar, 2001).

Health Effects and Benefits

Green tea has many well-known effects and benefits. It has

anti-diabetic, hypocholesterolemic, anti-inflammatory, anti-car-

cinogenic, anti-cavity, thermogenic, probiotic, antimicrobial

and antiviral properties (Song & Seong, 2007; Molinari et al.,

2006).

Population-based and in vitro studies have been conducted to

show that catechins may help kill cancerous cells and stop their

aberrant growth in bladder, breast, ovarian, colorectal, esopha-

geal, lung, pancreatic, prostate, and skin cancer (University of

Maryland Medical Center, 2011).

Green tea’s antimicrobial properties are effective against a

variety of microbes, which include Helicobacter pylori (gastric

malignancy), Staphylococcus aureus (MRSA), Oral strepto-

cocci (dental caries), Mycobacterium tuberculosis (tuberculo-

sis), Bacillus cereus (food poisoning), Escherichia coli O157

(severe diarrhea and kidney failure), Legionella pneumophila

(pneumonia), Candida albicans (candidiasis), and Chlamydia

trachomatis (chlamydia) (Song & Seong, 2007).

Its antiviral properties are effective against HIV, influenza,

Epstein-Barr, Herpes, Hepatitis B and C, and Human T-cell

lymphotropic virus type 1 (HTLV-1; leads to adult T-cell leu-

kemia) (Song & Seong, 2007; Xu et al., 2008; Ciesek et al.,

2011). Because the use of antiviral drugs can cause the emer-

gence of drug-resistant viral strains, the cultural adoption of

green tea consumption appears to be a potential effective anti-

infection agent with minimal (if any) negative consequences.

Materials and Methods

For this paper, I used the PubMed search engine to find and

analyze studies designed to determine the effect that phytoche-

micals extracted from green tea had on various infections. I nar-

rowed my selection by reviewing papers that focused on viral

infections, and that were conducted as either a population or in

vitro study using human cells. The studies I selected were pub-

lished between 2008 and 2011.

Hepatitis B and C

Hepatitis is the irritation and inflammation of the liver due to

a viral infection. The Hepatitis B virus (HBV) is endemic in

Asia (Xu et al., 2008). An in vitro study conducted by Xu et al.

(2008) involved the combination of natural green tea extract

with an HBV cell line (HEPG2-N10) to determine the 50% ef-

fective concentration on the expression of viral antigens

(HBsAg and HBeAg), extracellular HBV DNA and intracellu-

lar replicative intermediates and nuclear covalent closed circu-

lar DNA, and HBV mRNAs. The study yielded results for the

50% effective concentration of green tea extract on HBsAg

(5.02 g/mL), HbeAg (5.681 g/mL), extracellular HBV DNA

(19.81 g/mL) and intracellular HBV DNA (10.79 g/mL). The

authors concluded that green tea extract and EGCG in particu-

lar inhibits the Hepatitis B virus in vitro.

The Hepatitis C virus (HCV) is a major cause of liver cirrho-

sis and hepatocellular carcinoma (Ciesek et al., 2011). Another

in vitro study conducted by Ciesek et al. (2011) combined 100

M of epigallocatechin-3-gallate (EGCG) to a medium of in-

fected cells (hepatoma cell lines and primary human hepato-

cytes). EGCG was identified as an inhibitor of HCV entry by

inhibiting infectivity of HCV during inoculation and disrupting

the initial step of HCV cell entry by inhibiting viral attachment

to the cell.

Influenza

Influenza is due to the infection of the respiratory system

(nose, throat, and lungs) by RNA viruses. Evidence has been

found to suggest that catechins, especially EGCG, have viruci-

dal effects on all three major human influenza viruses (A/H1N1,

A/H3N2 and B) (Song et al., 2005).

In a population-based study of schoolchildren in Kikugawa

City, Japan, Park et al. (2011) distributed an anonymous ques-

tionnaire survey twice during the 2008-2009 endemic type A

influenza season to 2050 elementary school students in a tea

plantation area in Japan. The age range of the participants was 6

to 13 years old. The study found that an adjusted odds ratio in-

versely associated with consumption of 1 cup/day to <3 cups/

day was .62 in cases of confirmed influenza by the antigen test,

and that associated with consumption of 3 - 5 cups/day compar-

ed with <1 cup/day was .54. There was no significant assump-

tion with the consumption of >5 cups/day. Therefore, Park et al.

(2011) concluded that the consumption of 1 - 5 cups/day of

green tea might prevent influenza infection in children.

A randomized, double blind placebo-controlled trial of 197

healthcare workers in three healthcare facilities for the elderly

was conducted during the 2009-2010 influenza season in Higa-

shimurayama, Japan by Matsumoto et al. (2011) The partici-

pants were divided into two groups: green tea catechins/the-

anine (N = 98) and control (N = 99). The first group received

capsules containing 378 mg of catechins and 210 mg of the-

anine to take daily. The control group received placebos. The

incidence of clinically defined influenza infection and labora-

tory-confirmed influenza with viral antigen, and the time for

which the patient was free from clinically defined influenza

infection were measured. They found that 4 participants in the

experimental group and 13 from the control group reported in-

cidences of clinically defined influenza infection. On the other

hand, only 1 of the experimental group and 5 from the control

group had laboratory-confirmed influenza, which is statistically

insignificant. Matsumoto et al. concluded that green tea cate-

chins and theanine (an amino acid found naturally in green tea)

might be effective prophylaxis for influenza infection among

healthcare workers for the elderly.

Human Immunodeficiency Virus (HIV)

HIV is an infection caused by a lentivirus that incorporates

the viral RNA sequence into the host genome by reverse tran-

scription. It gradually destroys the immune system and causes

acquired immunodeficiency syndrome (AIDS). Catechins have

inhibitory effects throughout the infection life cycle. They

compromise the physical integrity of the virion, bind to the host

cells, blocking post-absorption entry, and prevent the replica-

tion of the viral genome by inhibiting reverse transcriptase

(Pandey & Rizvi 2009). EGCG has been found to bind directly

to CD4 (the glycoproteins found on the surface of T lympho-

cytes), which consequently, inhibits gp120 binding.

One study conducted by Li et al. (2011) combined EGCG to

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HeLa-CD4-LTR-beta-gal cells. They found that the 50% effec-

tive concentration was relatively low (1.6 and 2.0 M) for both

HIV-1 (IIIB) and HIV-2 (EHO) infections. Using a time-of-

addition assay, it was determined that the inhibitory profile of

EGCG was identical to that of a non-nucleoside reverse tran-

scriptase inhibitor, MKC-442. When a nucleoside reverse tran-

scriptase inhibitor, 3’-azido-3’-deoxythymidine or AZT, was

also added to the cell culture, it was discovered that EGCG and

AZT synergistically inhibited HIV infection. They concluded

that EGCG might act mainly as an allosteric reverse transcrip-

tase inhibitor (Li et al., 2011).

Another in vitro study was conducted by adding EGCG to

peripheral blood mononuclear cell cultures. The study was done

by Hauber et al. (2009) to determine if EGCG had an effect on

semen-derived enhancement of HIV infection. Peptide fragments,

derived from prostatic acidic phosphatase, are secreted in large

amounts into human semen and form amyloid fibrils that cap-

ture HIV virions and direct them to target cells (Hauber et al.,

2009). The study showed that EGCG targets semen-derived en-

hancer of virus infection (SEVI) for degradation, inhibits its ac-

tivity and abrogates semen-mediated enhancement of HIV-1 in-

fection in the absence of cellular toxicity.

Concerns and Criticisms

The consumption of green tea and its potential anti-infectious

properties have been criticized for several reasons. The first is

the cultural factors that may confound these studies. Because

green tea is more widely consumed in East Asia, especially in

China and Japan where the tea culture is well embraced, there is

a worry that the link made between green tea catechins and its

health benefits may actually be due to other cultural practices

shared by these populations, such as another staple in their diet.

Because studies have been conducted in human cell cultures,

there is evidence to suggest that green tea catechins do provide

these health benefits as a property of their catechins and that

they may be amplified or isolated in certain cultures because of

its green tea culture.

Another critique of catechins is its bioavailability to humans

by drinking green tea. But through these studies presented, it

appears that an individual could get several health benefits from

drinking less than 5 cups of green tea daily, not only for green

tea’s invigorating, refreshing qualities but also as an aid in di-

gestion, and prevention of viral infections and cancer.

As with all phytochemicals, there is a concern that excessive

consumptions will have detrimental effects. Due to the obesity

epidemic, there is an increasing interest in diet products and

weight-less supplement, which include green tea extract pack-

aged in pills. A case report conducted by Molinari et al. (2006)

presented a 44-year-old female of European descent suffering

from worsening acute liver failure. She was participating in a

weight-loss program for 6 months that recommended increased

physical activity and the intake of dietary supplements contain-

ing green tea extract with a concentration of 720 mg/day. Re-

ports like this one have shown a correlation between patients

presented with marked liver toxicity in the form of acute heap-

titis and the consumption of supplements containing green tea

extracts. These cases of toxicity were limited to individuals and

resolved after discontinuation of the supplementation (Molinari

et al., 2006). This underlies the necessity for an increase in

awareness and education of the use of supplementation. Based

on a preliminary search, there are no studies that have presented

any adverse consequences of drinking green tea suggesting that

it is most likely safe to consume green tea as a beverage with

little to no risk.

The Coevolution of Humans and Plants

The interactions between Camellia sinensis and humans have

lasted for thousands of years and the strength of these interac-

tions varies between cultures. As is self-evident, green tea has

grown into a culture that encompasses many practices that

range from its cultivation to its consumption in China. This

relationship between humans and Camellia sinensis is high-

lighted by the numerous health benefits green tea is found to

have. But this is only one aspect of their interconnected history.

The cultivation of Camellia sinensis has outlined the role of

humans in the evolution of this species. Through artificial se-

lection, certain traits have been selected for over time, which

has led to less diversity within the species and a divergence ge-

notypically and phenotypically of domesticates from their wild

counterparts. Although the effect of humans over plants is

much more apparent phenotypically, plants have an effect on

humans, as well. The phytochemicals produced by plants must

create an appeal for humans to invest the time and energy into

the care of the plant.

Since its discovery, Camellia sinensis has been domesticated

in a way that appealed to humans who chose certain mutations

that they found desirable, which resulted in the increase in pre-

valence of particular mutated genes. These mutated genes are

preserved in the species and encode proteins that may affect

humans’ own biology and behavior. Catechins are necessary for

the plant’s growth, reproduction, and defense; therefore, it is

likely that the catechin level has increased over time because of

its integration into the culture, for only the most resilient strains

would have survived and been selected for by the cultivators.

Also, green tea has been used for its medicinal properties al-

most immediately after its discovery. This purposeful use of

green tea may have resulted in other behaviors in humans that

led to the selection for plants with higher catechin levels.

As indicated by the Chinese manual, the Tea Classic, humans

play an active role in determining when and where the plant

should be grown and how it should be cultivated. The plant is

most suitable to hot and humid climates and is cultivated in low

rows for easy harvesting (Pettigrew, 2004). Although fermenta-

tion makes the export of tea easier, the unfermented version of

tea remains the preferred tea in the East and is increasing in

popularity in other parts of the world. This preference may be a

result of humans’ conscious or subconscious desire for cate-

chins and their health benefits.

Conclusion

The consumption of green tea has a history that spans back to

over 5000 years. Traditionally, it was prescribed for a number

of ailments while also being consumed for its refreshing quali-

ties and the prevention of future health problems. Starting in

China, the green tea craze has expanded worldwide to become

the second most consumed drink after water. This increase in

popularity is in part due to the increasing awareness of green

tea’s many health benefits. Besides its soothing and invigorat-

ing capabilities, it is consumed for its anti-diabetic, hypocho-

lesterolemic, anti-inflammatory, anti-carcinogenic, anti-cavity,

antimicrobial and antiviral properties (Song & Seong, 2007).

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The active ingredients in green tea that contributes to these pro-

perties are the phytochemicals called catechins, in particular

epigallocatechin gallate, the main and most active catechins.

Studies have shown that EGCG is effective in preventing infec-

tion by the hepatitis, influenza, and human immunodeficiency

viruses. Because EGCG affects the viral infection process ra-

ther than targeting the virus specifically, drinking green tea may

be a potential effective anti-infection agent without the negative

consequences of anti-viral drugs/treatment that leads to the de-

velopment of new drug-resistant strains and a constant need for

the development of new drugs.

The education of people about the numerous benefits of

drinking green tea may lead to the adoption of this practice by

other cultures. The change is small and easy to do. Green tea is

widely available and is often processed in a way that it is pre-

served for a great length of time. By making green tea more

available outside of coffee shops, Chinese restaurants, and gro-

cery stores, there is a potential for a cascading effect to occur

resulting in many positive changes, such as the reduced reliance

on commercial drugs, and the reduced incidence and prevalence

rates in high cholesterol, diabetes, cancer, cavities, and infec-

tions. Green tea has great potential in improving the health of

people worldwide. With its rapid increase in popularity, a heal-

thier world may be on the horizon.

Acknowledgements

The author would like to thank the editors of this manuscript

and the reviewers who contributed their time. The author would

also like to acknowledge Dr. Fatimah Jackson for her guidance,

support and assistance throughout the research process.

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