Photoprotective effects of green tea polyphenols
Nabiha Yusuf1,2, Cynthia Irby1, Santosh K. Katiyar1,2, Craig A. Elmets1,2
1Department of Dermatology and
2The UAB Skin Diseases Research Center, University of Alabama at Birmingham, Birmingham AL 35294, USA
Non-melanoma skin cancer is the most common
malignancy in humans and is equivalent to the incidence
of malignancies in all other organs combined in the
United States. Current methods of prevention depend
on sunscreens in humans, efficacy of which is largely
undetermined for non-melanoma skin cancers. Green
tea polyphenols have the greatest effect with respect to
chemoprevention and have been found to be most
potent at suppressing the carcinogenic activity of UV
radiation. They protect against many of the other
damaging effects of UV radiation such as UV-induced
sunburn response, UV-induced immunosuppression and
photoaging of the skin. They exert their photoprotec-
tive effects by various cellular, molecular and biochem-
ical mechanisms in in vitro and in vivo systems. Green
tea polyphenols thus have the potential, when used in
conjunction with traditional sunscreens, to further
protect the skin against the adverse effects of ultra-
Key words: green tea polyphenols; photoprotection;
skin cancer; UV radiation.
alone, over 1.3 million new cases of cutaneous squa-
mous cell and basal cell carcinomas are diagnosed
each year (1). This is equivalent to the incidence of
malignancies in all other organs combined. It is
predicted that one in five Americans will develop at
least one basal cell or squamous cell carcinoma during
the course of their lifetime. The vast majority of these
– over 90% – are caused by overexposure to ultravio-
let radiation (2, 3). Moreover, the incidence of these
diseases is increasing rapidly (4–7). Over a 6-year
period in Minnesota, there was over a 53% increase
in the incidence of squamous cell carcinoma in men
and a 115% increase in women (6). Similar increases
in the incidence of both cutaneous squamous cell and
basal cell carcinoma have been reported from epide-
miological studies in New Mexico (7).
Although there are many ways in which non-mela-
noma skin cancers can be successfully treated, there is
increasing interest in developing new and better meth-
ods for their prevention. Current methods of preven-
tion include counseling patients to avoid sun exposure
during peak hours of ultra voilet (UV) intensity, to
wear broad-brimmed hats and long-sleeved clothing,
and to regularly apply sunscreens. It is important to
remember, however, that the efficacy of currently
available sunscreens is determined largely by their
on-melanoma skin cancer is the most common
malignancy in humans. In the United States
ability to protect against UV-induced sunburns, and
their chemopreventive activity, at least in humans, is
largely undetermined for non-melanoma skin cancers.
While not to deny the value of sunscreens in the
prevention of UV damage, it is important to note
that most sunscreens have only modest efficacy (8);
there is inconsistent patient compliance (9, 10); large
amounts of sunscreen are required to achieve the full
SPF value present on the label of the sunscreen (11);
and there is no effect of sunscreens on prior UV
damage. For these reasons, other agents are needed
that will protect against UV-induced skin cancer
development. One agent that has received particular
attention in this regard is green tea.
Green tea is manufactured from the fresh leaves of
the plant Camellia sinensis (12). The leaves of this
plant are fermented through a process that, for the
most part, prevents oxidation and polymerization of
the plant’s polyphenols. It is these compounds that are
thought to be the major chemopreventive mediators.
Green tea contains four major polyphenols: (?)-epi-
catechin (EC), (?)-epicatechin-3-gallate (ECG), (?)-
epigallocatechin (EGC), and (?)-epigallocatechin-3-
gallate (EGCG) (Fig. 1). It also contains other
agents that have chemopreventive activities. These
include caffeine, flavandiols, flavanoids, phenolic
acids as well as the alkaloids theobromine and theo-
phylline (13). It is the polyphenols, however, that have
Photodermatol Photoimmunol Photomed 2007; 23: 48–56
the greatest effect with respect to chemoprevention.
Black and oolong tea, the other two major types of
tea, also have chemopreventive activities, which are
attributed primarily to the caffeine, theaflavins and
thearubigins that they contain (12, 14, 15).
The stimulus for investigating green tea as a chemo-
preventive agent in non-melanoma skin cancer was
based on a series of epidemiological studies suggesting
that green tea prevents cancer in other organ systems
(16). For example, in areas of China in which esopha-
geal cancer rates are the highest, tea is infrequently
consumed (17). In addition, an inverse correlation has
been observed between tea intake and oropharyngeal
and esophageal cancers in postmenopausal women in
Iowa, where daily tea consumption was associated
with a greater than 50% lower risk (18). Tea con-
sumption has also been observed to reduce the risk for
cancers of the stomach, bladder and urinary tract, and
liver cancer. It is important to note, however, that
other studies have shown the opposite effect for some
malignancies (16). Green tea compound, ECG and
EGCG may be effective in treating human prostate
tumors in mice which were actually suppressed by
administration of EGCG. Similar EGCG-dependent
suppression was also found with human breast tumors
growing in mice (19).
Green tea and photocarcinogenesis
The first evidence that green tea polyphenols might
have a protective role in UV-induced skin cancer came
from studies by Wang et al., who showed that green
tea administered in the drinking water to SKH-1
hairless mice had a dose-dependent prolongation in
the mean time of tumor development when they were
subjected to a photocarcinogenesis protocol (20).
Similar observations were made with respect to topical
application of green tea polyphenols (20). A number
of other studies have confirmed these results (21–23).
Of the four major green tea polyphenols, EGCG has
been found to be the most potent at suppressing the
carcinogenic activity of UV radiation (21, 22). More-
over, the vehicle into which green tea polyphenols are
incorporated has a significant influence with hydro-
philic ointment having greater efficacy than other
The development of UV-induced skin cancers in
mice has been divided into the initiation, promotion
and progression stages. Green tea polyphenols have
been shown to have protective effects during each of
these stages (24–26).
Protective effects of green tea polyphenols in
other forms of UV damage in vivo
Green tea and its polyphenolic constituents protect
against many of the other damaging effects of UV
radiation. In mice, both systemic and topical admin-
istration of green tea polyphenols and EGCG were
found to protect against the UV-induced sunburn
response (27), UV-induced immunosuppression (27,
28) and photoaging of the skin (29). Similar results
with respect to sunburn were observed in human skin
that had been pretreated with a crude extract of green
tea or with EGCG.
In animal models, green tea polyphenols have an
ameliorative effect on photoaging as well (30). In
UVA-irradiated SKH-1 hairless mice, there was an
observable reduction in the amount of skin wrinkling.
Topical application of EGCG has been shown to
reduce UV-induced production of matrix metallopro-
teinases (MMP)-2, -3, -7 and -9, which are known to
degrade collagen and lead to photodamage (29).
Moreover, it is associated with a decrease in protein
oxidation in the skin which also seen with photoaged
The immunosuppressive effects of UV radiation on the
skin immune system are well recognized, and have been
implicated in the pathogenesis of non-melanoma skin
cancer (31). Using murine-allergic contact hypersensitiv-
ity as a model, topical application of green tea polyphe-
nols, either before or immediately after UV exposure, has
been shown to reverse the immunosuppressive effects of
UV, whereas topical application of green tea polyphenols
Fig.1. Chemical structures of major epicatechin deri-
vatives or polyphenols presenft in green tea.
Photoprotective effects of green tea polyphenols
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Accepted for publication 4 August 2006
Nabiha Yusuf, Ph.D.
Department of Dermatology
University of Alabama at Birmingham
1670 University Blvd.
VH 566A Box 202
Birmingham, AL 35294
Yusuf et al.