Biology Reference
In-Depth Information
17
Photoprotective Activity
of some Mexican Plants
Ana M. García-Bores,
1
Tzasná Hernández,
2
Amira R. Arciniegas,
3
José del Carmen Benítez,
4
M. Rosario Gonzalez,
4
Manuel López,
1
Alfonso Romo de Vivar
3
and José Guillermo Avila
1
*
3
Instituto de Química;
4
Laboratorio 1, UMF, Facultad de Estudios
Superiores-Iztacala, Universidad Nacional Autónoma de México
17.1
Introduction
effects of UVR in the skin can be divided
into acute (sunburn or erythema, phototoxic
reactions, photoallergic reactions and pho-
tosensitivity) and chronic (photo-ageing,
skin
In the past few decades several human
activities, such as the release into the envi-
ronment of chlorofluorocarbons, have led to
the diminution of the ozone layer. This has
resulted in an increase in the amount of
solar radiation reaching the earth's surface.
Ultraviolet radiation (UVR) from the sun is
divided into UVC (270-290 nm), UVB (290-
320 nm) and UVA (320-400 nm). The
amount of UVR that crosses the atmosphere
and reaches the earth is approximately 6%
of the sun's radiation. The radiation inten-
sity depends on several factors such as alti-
tude, latitude, season of the year, hour of the
day, cloudiness and light dispersion
(Goettsch
et al
., 1998; De Gruijil, 1999).
The skin is the body organ most exposed
to UVR. Several studies
in vitro
and
in vivo
have demonstrated that UVB causes dam-
age to various molecules and cellular com-
ponents, and produces alterations in cell
functions. The DNA is the main target; its
damage can lead to skin cancer development
(Marrot and Meunier, 2008). The harmful
cancer
and
immunosuppression)
(Matsumura
and
Ananthaswamy,
2004;
Adhami
et al
., 2008).
Experimental and epidemiologic evi-
dences have shown the direct correlation
between exposure to UVB with squamous
cell cancer (SCC), basal cell cancer (BCC)
and melanoma (Black
et al
., 1997; De Grujil,
1999; Armastrong and Kricker, 2001;
Matsumura and Ananthaswamy, 2004).
Incidence of skin cancer has increased so
fast in the last few decades that it has been
considered as the silent epidemic of the
20th century (Stratton
et al
., 2000).
Cutaneous overexposure to solar radiation,
especially its UVR component, can cause
several skin-related disorders. In Mexico,
skin cancer ranks second in frequency
among all malignancies, which constitutes
13.6% in the last report of the 'Registro
Histopatológico de Neoplasias Malignas'
(Secretaría de Salud, 2001). Non-melanoma
* E-mail: tuncomaclovio2000@yahoo.com.mx
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