Health benefits of green tea: A mini review

Abstract

For gaining popularity and greater demand for medicinal plants, various medicinal plants are taken into considerations for therapeutic research. Green tea is the processed natural product consumed as a healthy drink for refreshment worldwide. Its leaf is consumed which has medicinal values such as antioxidant activity, antimicrobial activity and it has several phytochemical constituents. It contains 15-20% protein and 1-4% amino acids, 5-7 % carbohydrates and 10-25 % major antioxidant catching tannins. Thousands of bioactive components are present in green tea as polyphenols which is the key factor for preventing many diseases. The objective of this manuscript is to review of therapeutic properties of green tea.

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Journal of Entomology and Zoology Studies 2020; 8(1): 1424-1430
E-ISSN: 2320-7078
P-ISSN: 2349-6800
JEZS 2020; 8(1): 1424-1430
© 2020 JEZS
Received: 20-11-2019
Accepted: 24-12-2019
Asik Ikbal
Department of Fish Processing
Technology, Faculty of Fishery
Sciences, West Bengal University
of Animal and Fishery Sciences
Chakgaria, Kolkata,
West Bengal, India
Satarupa Roy
New Zealand Fresh & Natural, 6,
Waterloo Street, Kolkata,
West Bengal, India
Keya Pati
Department of Fish Processing
Technology, Faculty of Fishery
Sciences, West Bengal University
of Animal and Fishery Sciences
Chakgaria, Kolkata, West
Bengal, India
Corresponding Author:
Satarupa Roy
New Zealand Fresh & Natural, 6,
Waterloo Street, Kolkata, West
Bengal, India
Health benefits of green tea: A mini review
Asik Ikbal, Satarupa Roy and Keya Pati
Abstract
For gaining popularity and greater demand for medicinal plants, various medicinal plants are taken into
considerations for therapeutic research. Green tea is the processed natural product consumed as a healthy
drink for refreshment worldwide. Its leaf is consumed which has medicinal values such as antioxidant
activity, antimicrobial activity and it has several phytochemical constituents. It contains 15-20% protein
and 1-4% amino acids, 5-7 % carbohydrates and 10-25 % major antioxidant catching tannins. Thousands
of bioactive components are present in green tea as polyphenols which is the key factor for preventing
many diseases. The objective of this manuscript is to review of therapeutic properties of green tea.
Keywords: Green tea, phytochemical constituents, antioxidant properties, antimicrobial properties
Introduction
Green Tea is non-toxic, non-fermented and widespread therapeutic beverages consumed
around the world produced from the leaf of the plant called “Camellia sinensis” which is found
mainly in Chinaand in Southeast Asia (Molan, 2013) [1]. It tends to be devoured as a drink,
which has many beneficial wellbeing effects or concentrate from its leaves can be made for
medicinal use (Namita et al., 2012; Narotzki et al., 2012) [2, 3]. Green tea has been consumed
over the centuries in India, China, Japan, and Thailand as tea which is a good source of various
phytochemicals and the most common drink in the world after water (Fujiki et al., 2002) [4].
Recently, green tea has been acquired great attention in pharmacological and food industries
due to some beneficial effects including antimicrobial, antioxidant and prebiotic activities and
promotes human health (Zou et al., 2014; Su et al., 2008) [5, 6].
Tea flavanols have recently received much attention owing to their various biological exercises
(Chen et al., 2001) [7]. Their beneficial properties are thought to be included antioxidants
(Navas et al., 2005) [8], antimutagenic (Halder et al., 2005) [9], anticarcinogenic (Zhu et al.,
2005) [10] and antibacterial (An et al., 2004) [11] effects (Erol et al., 2009) [12]. Antioxidant has a
significant job in lessening free radical-intervened debasement of cells and tissues in the
organism (Jin et al., 2004; Wongkham et al., 2001; Almajano et al., 2008) [13-15].
Green tea, which has mitigating, hostile to tumor, antioxidative and antimicrobial properties, is
considered as a healthy product with its utilization connected to bring down rates of all these
different obsessive conditions (Bansal et al., 2013) [16]. Along with the thousands of bioactive
compounds, the most significant bioactive constituents of green tea are polyphenols or
flavonoids which play a key role in the prevention and treatment of many diseases. Green tea
is framed when the freshly picked leaves are being steamed, rolled, dried and burned, therefore
the chemical composition of it, including polyphenols, differs very little from the fresh tea
leaves (Wheeler and Wheeler 2004) [17].
Tea polyphenols, especially the catechins are potent antimicrobial and antioxidant agents with
positive effects on human health as well as fish health too (Boran et al., 2015; Barbosa et al.,
2007) [18, 19]. Green tea contains between 30 and 40 percent of water-extractable polyphenols,
while black tea has 3 to 10 percent which varies according to climate, season or variety
(Wanasundara and Shahidi, 1998; Archana et al., 2011) [20, 21]. The phytochemical screening of
tea revealed the presence of alkaloids, saponins, tannins, catechin, and polyphenols (Mbata et
al., 2008) [22]. Studies have shown that the antioxidant property of green tea extract is present
because of high quantity of catechins that are chemically defined as flavan-3-ols (Balentine et
al., 1997) [23] and four polyphenol compounds, Epigallocatechin gallate (EGCG), Epicatechin
gallate (ECG), Epigallocatechin (EGC) and Epicatechin (EC) (Frei and Higdon, 2003;
Zandiand Gondon, 1999) [24, 25]. Among them (-)-Epigallocatechin-3-gallate (EGCG) is the
main and biologically most potent and the most luxuriant component. (Yang and Koo, 1997)
[26].

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The tea catechins are free radical scavengers, metal chelators,
inhibitors of transcription factors, and enzymes. Therefore,
green tea extracts have been used as natural antioxidants,
antibacterial and antiviral agents (Manzocco et al., 1998;
Tang and Meydani, 2001) [27, 28]. Also, it has been reported
that green tea extract has anticarcinogenic and antimutagenic
activity (Yang et al., 2000) [29]. Green tea extracts also contain
caffeine, vitamins, amino acids, the anine, volatiles, and
minerals (da Silva Pinto, 2013; Davidson et al., 2005) [30, 31].
So, Green tea is beneficial to serve as a natural food
antioxidant.
During the last decade, the effects of tea and tea polyphenols
were extensively investigated and studies showed that tea is
capable of lowering the risk of cardiovascular diseases and
cancers (Huo et al., 2008; Mukamal et al., 2007) [32, 33],
reducing body fat, systolic blood pressure (SBP), and low-
density lipoprotein (LDL) cholesterol (Nagao et al., 2007) [34].
Among age-associated pathologies and neurodegenerative
diseases, green tea was shown to confer significant protection
against Parkinson’s disease and Alzheimer’s disease (Chang
and Jiang, 2007; Rezai-Zadeh et al., 2005) [35, 36]. On the other
way, continuous consumption of tea by mothers during
pregnancy might be associated with an increased risk of
preeclampsia, especially severe preeclampsia (Wei et al.,
2009; Dutta et al., 2013) [37, 38].
Phytochemical constituents
There are mainly three types of tea variants available and
consumed worldwide. Among them 78% is black, 20% is
green, and 2% is oolong tea originates from the same Phyto-
species (Chan et al., 2011; Koech et al., 2017) [39, 40]. Green
tea has been widely studied, analyzed including all the
varieties as it is the non-fermented retaining green color and
almost all phytochemical contents (Manning and Roberts,
2003) [41].
The chemical composition of green tea is made up of 15-20%
protein and 1-4% amino acids on a dry weight basis. Amino
acids like glutamic acid, tryptophan, glycine, serine, aspartic
acid, tyrosine, valine, leucine, threonine, arginine, and lysine
and carbohydrates (5-7% in dry weight basis) such as
cellulose, pectins, glucose, fructose, sucroseare partly
included in green tea (Senanayake, 2013) [42]. Other green tea-
compounds with interest in human health such as fluorine,
caffeine, minerals, trace elements such as chromium and
manganese. (Kristanti and Punbusayakul, 2008) [43]. It
contains trace elements in lipid form (linoleic acid, alpha-
linolenic acid), sterols (stigmasterol), vitamins (B, C, E),
xanthine bases (caffeine, theophylline), pigments
(chlorophyll, carotenoids), volatile compounds (aldehyde,
alcohol, esters, lactones, hydrocarbons).
Fig 1: Composition (%) of green tea (Chacko et al., 2010) [44]
Green tea contains polyphenols which include flavonols,
flavonndiol, flavonoids, and phenolic acids (Jo et al., 2012)
[45]. The principal catechins present in green tea such as (-)-
epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin-
3-gallate (ECG), (-)-epigallocatechin-3-gallate (EGCG) and (-
)-gallocatechin gallate (GCG) are indicated as major part of
biologically active substances (Ho et al., 1994; Sharma et al.,
2014) [46, 47]. A large number of catechin tannins (10-25%) are
available in green tea. EGCG is the most common polyphenol
found in green tea and represents up to 10% of its dry weight
and includes 60-70% of its total catechins. Many of the green
tea has health promotion abilities that are attributed to EGCG
(Patil et al., 2016) [48]. EGCG and other catechins show strong
antioxidant activities due to their reduction potential of single
electrons. Free radicals are harmful and reactive molecules
that become unstable from this unpaired electron. They are
involved in diseases from blood clots to cancer (Bancirova,
2010) [49].
Table 1: Phenolic Components of Green Tea (% Dry Weight) (Rice-
Evans, 1999) [50]
Catechins
30-42%
(i-v)
i. Epigallocatechin gallate (11.2%)
ii. Epigallocatechin (10.3%)
iii. Epicatechin gallate (2.3%)
iv. Epicatechin (2.5%)
v. Catechin (0.5%)
Flavonols
2%
Simple polyphenols
2%

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Fig 2: Structures of catechin constituents of green tea (Camellia
sinensis). (Manning and Roberts, 2003) [41]
Antioxidant properties:
An antioxidant is a substance that inhibits lipid oxidation by
quenching the formation of free radicals or by producing
more free radicals that can spread the oxidation reaction.
(Senanayake, 2013) [42].The antioxidant activity of green tea
polyphenols is predominantly due to the combination of
aromatic rings and hydroxyl groups, which synthesize their
chemical structure and consequently bind and neutralize lipid-
free radicals by these hydroxyl groups. Numerous researches
have been exhibited in different aspects on antioxidant
activity of green tea polyphenols which are exceptional
electron donors and are effective scavengers of
physiologically reactive oxygen species (ROS) in vitro,
including superoxide anions (Guo et al., 1999; Yokozawa et
al., 2002; Nanjo et al., 1996; Pon and Liu, 2008) [51-54],
peroxyl radicals, and singlet oxygen. Consequently, green tea
is the most effective against beta-carotene oxidation as far as
the antioxidant property is concerned and can serve as a
natural source of free radical scavengers and cancer
prevention agent (Senanayake, 2013; Jo et al., 2012) [42, 45].
The most potent antioxidant polyphenol of green tea is EGC
(Zuo et al., 2006; Koech et al., 2017) [10, 40]. Significant levels
of bioactive catechins are available in green tea that has the
ability to stabilize the free radicals by providing hydrogen
ions. The high antioxidative effect of polyphenols in green tea
is because of the closeness of phenolic hydroxyl groups in
their structures that make them potent free radical scavengers
(Tariq and Reyaz, 2013) [55]. This hydroxylation built a higher
volume of stability on the catechin phenoxyl radicals by
participating in electron delocalization that is asignificant
feature of the anti-radical potential. That is why radical
scavenging is high in the gallocatechin including EGCG and
EGC (Koech et al., 2017) [40]. Green tea catechins are
performed as water-soluble antioxidants as Trolox and
ascorbic acid, have been shown to act as active antioxidants in
bulk oils and as prooxidants in oil-in-water emulsions
(Senanayake, 2013; Frankel et al., 1997) [42, 56].
Green tea extract is a promising wellspring of natural
antioxidants that has been effectively utilized not exclusively
to enhance flavour in addition to broaden the shelf-life of
various food products (Senanayake, 2013) [42]. Green tea
otherwise acts as a preventative agent of some common
human health disorders (Hossain and Mahmood, 2014) [57].
Green tea contains considerable amounts of catechin tannin
which is a powerful, water-soluble polyphenol and
antioxidant that is easily oxidized. From a single cup of green
tea, one canbe benefitted from 10-40 mg of polyphenols
(antioxidants) (http://www.greenteanutritionfacts.com.25
September, 2019) [58]. According to Cao et al. (1996) [59],
green and black tea had much higher antioxidant activity
against free radicals than all the commercially available
vegetables (Senanayake, 2013) [42].
Many studies have been reported on green tea that has much
higher antioxidant activities against free radicals which are
not found in vegetables. It is measured mainly by the Oxygen
Radical Absorbance Capacity (ORAC) assay, DPPH (2, 2-
diphenyl-1-picrylhydrazyl) radical scavenging assays and
Trolox equivalent antioxidant capacity (TEAC) assay [Rice-
Evans,1999; Cao et al., 1996; Tsai et al., 2008) [50-60].
Fig 3: Reactive antioxidant properties of green tea (Rice-Evans, 1999) [50]

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*TEAC is the millimolar concentration of Trolox (reference
standard) having the equivalent antioxidant activity to a 1 m
Mconcentration of the antioxidant compound or defined
concentration or volume of food extract/beverage under
investigation.
Antimicrobial properties
Resistance to antimicrobial agents has been becoming
harmful to the environment and accelerating the global
problem (Cushnie and Lamb, 2005) [61]. Nowadays many
antimicrobial drugs cannot destroy their pathogenic
microorganisms as they becoming resistant. Therefore,
researchers are finding some new drugs from mangrove
species to control the pathogens due to the presence of
antimicrobial compounds (Clercq, 2001; Poole, 2001) [62, 63].
The accompanying review will look at the antimicrobial
action of green tea polyphenols, characteristic natural
compounds, possessing an assorted scope of pharmacological
properties. The antimicrobial activity of tea was first
established almost 100 years ago by McNaught (1906) [64]
(Taylor et al., 2005) [65]. Many clashing reports of
presumptive antimicrobial activity detect that the specific
antibacterial spectrum of green tea is actually difficult to
assess.
Tea exhibits antimicrobial properties, which are ascribed
predominantly to its polyphenols (Dias et al., 2013) [66]. The
degree of animation depends on the bacterial species and the
polyphenol structure (Campos et al., 2003; Taguri et al.,
2004) [67, 68]. The antibacterial activity of green tea is being
gradually documented and first reported from Japan by using
Japanese tea against various diarrheal pathogens (Hossain and
Mahmood, 2014) [57]. The revelation of potent plant and plant
seed extracts can effectively avert bacterial growth.
Therefore, This has prompted an expanding enthusiasm
among the researchers to evaluate the capability of green tea
seed to inhibit the growth of some species of fish pathogenic
bacteria (Y. Ruckeri, P. Putida, P. Luteola, A. Hydrophilaand
L. Anguillarum) with the intention of assessing them as
possible disease preventive measures in aquaculture (Halder
et al., 2005) [9]. Good evidence suggests that the catechin
components of green tea are responsible for the observed
antibacterial activity owing to the presence of EGC, EGCG,
and ECG constituents (Tsai et al., 2008; Yam et al. 1997;
Hara 2001) [59, 69, 70]. Gram-negative bacteria seem to be more
resistant to polyphenols than Gram-positive bacteria, due to
differences in the exterior membrane (Negi et al., 2003) [71].
Yang et al. (2011) [72] reported no antibacterial activity
occurred against Gram-negative E. Coli, S. Typhi, and P.
Aeruginosa. This study also disclosed that green tea extracts
inhibited the growth of Gram-positive M. Luteus, S. Aureus,
and B. Cereus, with M. Luteus being most delicate (Bansal et
al., 2013) [16]. Su et al. (2008) [6] also are of the view that the
antimicrobial activity of the green tea extract against the
pathogenic bacteria Staphylococcus aureus, Streptococcus
pyogenes, and E. Coli. Hara-Kudo et al. (2005) [73] revealed
the antibacterial effects of major green tea polyphenols using
Clostridium and Bacillus spores where C. Botulinum and C.
Butyricum spores were diminished in number while no effect
was shown in Bacillus cereus spores (Wongkham et al., 2001)
[14]. Only 100 mg green tea/ml is able to inhibit S.
Typhimurium, whereas twice the tea concentration is needed
for the inhibitory effect to be observed for E. Coli (Yam et al.,
1997; Kim and Fung, 2004) [69, 74]. The main components
responsible for the antimicrobial activity are EGCG and
EGC.EGCG at 10–100 μmhas shown to reduce E. Coli
growth by approximately 50% (Gramzaand Korczak, 2005)
[75]. Due to the highest antioxidant activity (TEAC values), the
antimicrobial activity of nonfermented tea is higher than that
of semi-fermented or fermented tea (Nazer et al., 2005) [76].
Attributable to the far-reaching capacity of green tea to
repress spore germination of plant pathogens and proposed for
use against contagious fungal pathogens. The antifungal
impacts of EGCG were mainly studied against yeasts such as
Candida spp. and molds such as dermatophytes (Steinmann et
al., 2013) [77]. As of late, data relates between green tea
polyphenols and irresistible aspergilli or other human-
pathogenic zygomycetes which cause dysfunction of the local
defense systemand infections of the skin, hair, and nails of
humans and animals are lacking (Pappas etal.,2009) [78]. In an
in vitro study, it was revealed that EGCG, EGC, and ECG
cause metabolic instability of C. Albicans (Evensen and
Braun, 2009) [79].
The mechanism of antiviral action of polyphenolic
compounds is based on various capacities to go about as
antioxidant agents, to inhibit proteinaceous enzymes, to
disrupt cell membranes, to avoid viral binding and penetration
into cells, and to trigger the host cell. EGCG hinders
infections by direct authoritative to biological molecules and
persuades agglutination of the flu infection preventing their
adsorption to target (Friedman, 2007) [80]. The antiviral
mechanism of EGCG has been analyzed against endemic
HBV (Hepatitis B virus) infection (Heet al., 2011; Wang et
al., 2007) [81, 82]. Many reports demonstrated that green tea
catechin, EGCG is the most active compound against HIV
infectious diseases (Hamza and Zhan, 2006) [83]. Furthermore,
the evaluation has also been done with herpes simplex virus
(HSV) and bovine coronavirus (BCV) to realize the resistance
power of antiviral activity and therapeutic efficiency of
catechin polyphenols (Matsumoto et al., 2005) [84].
Anticarcinogenic activity
With time, Polyphenols are turning into the issue of medicinal
research. They have been accounted for to have numerous
helpful properties, including mitigating action, compound
hindrance, antimicrobial activity (Harborne and Baxter, 1999)
[85], antiallergic activity, antioxidant activity (Elliott and
Chithan, 2017) [86], cell reinforcement action, vascular action,
and cytotoxic antitumor action (Harborne and Williams,
2000) [87]. It isn't bewildering, in this way, leading
pharmaceutical organizations tend to focus their efforts on
improving antimicrobial agents in established classes in
setting up classes due to antimicrobial obstruction (Taylor et
al., 2002) [88].
Be that as it may, the accessible chemotherapy portfolio, it
has been recognized that researchers are approaching the end
of the activity in terms of alterations in the structure of
parents. Thusly, an intrigue was made for the improvement of
new classes of drugs that work in various objective
destinations for those as of now being utilized (Cushnie and
Lamb, 2005) [61]. Ongoing studies and others have found that
isolated green tea polyphenols have anticarcinogenic activity.
The effects of green tea as a malignant growth chemo-
preventive agent in a wide range of animal models are of
impressive intrigue. The oral administration of green tea
inhibits the formation of chemically induced tumors in several
models (Ho et al., 1994) [46]. Green tea components can
prevent the formation of carcinogens from forerunner
substances by rummaging cancer-causing electrophiles. (Han

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and Xu, 1990) [89]. Researchers have investigated that the
freeze-dried green tea containing EGCG turns away
carcinogenesis in rodents (Tariq and Reyaz, 2013) [55].
Various scientists have subsequently reported in this manner
covered the preventive impacts of green tea, positive or
negative, against human malignant growths, in view of
epidemiological examinations. Specifically, esophageal
cancer in urban Shanghai was averted with green tea
consumption (over 150 g tea leaves per month) (Amarowicz
et al., 2005) [90]. Dr Waun Ki Hong started his clinical
investigations of green tea extricate with a part of U.S.
population that had not recently been expending green tea. In
1997, the US Federal Drug Administration (FDA) conceded
consent for a Phase I clinical preliminary with green tea
containers, which were produced by a Japanese Tea
Company, ITO EN (Molan, 2013) [1]. Green tea is an
exceptional cancer-preventive prescription with two features
as refreshment and medication. Herbal remedies, including
green tea, are the same old thing, yet by presenting the idea of
malignant growth counteractive action that green tea spares
individuals' lives.
Conclusion
It can be concluded that green tea has several health benefits.
It is the reach source of phytonutrients like flavonoids,
phenolic acids, polyphenols, and catechin tannins. Green tea
also has several hydrophilic antioxidants properties as Trolox
and free radical scavengers. Green tea is very good in
consumption as a morning drink. It has a sufficient amount of
caffeine to give you a good morning energy boost. Unlike
coffee, tea contains an amino acid L-theanine, that prevents
caffeine rush and gives you the energy to sustain throughout
several hours instead.
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