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Effect of alcoholic extract of aloe vera plant on serum testosterone and
gonadotropin levels in rats
Karimi Jashni H*1, Najmadini N2, Hooshmand F3
Received: 01/01/2011
Revised: 03/12/2012
Accepted: 04/20/2012
1. Dept. of Anatomy, School of Medicine, Jahrom University of Medical Sciences, Jahrom, Iran
2. Dept. of Evolutionary Biology, Azad University of Jahrom, Jahrom, Iran
3. Dept. of Pathology, School of Medicine, Jahrom University of Medical Sciences, Jahrom, Iran
Journal of Jahrom University of Medical Sciences, Vol. 10, No. 2, Summer 2012
Abstract
J Jahrom Univ Med Sci 2012; 10(2):1-7
Introduction:
Aloe vera plant’s beneficial effect on diabetes, burns, wounds, and gastrointestinal diseases has
been proved. In this study, the effect of aloe vera extract on serum testosterone and gonadotropin
levels was investigated in rats.
Materials and Methods:
In this experimental study, 45 adult male Westar rats with the average weight of 200 ± 20 g were
randomly divided into 5 groups, including control, sham and experimental groups 1, 2, 3, which
received orally 50, 100, 200 mg /kg/bw aloe vera alcoholic extract per day respectively for 30
days. The rats were anaesthetized with ether, and blood was taken from the heart. Serum was
separated and serum level of hormones LH, FSH and testosterone were measured by
radioimmunoassay. The data were analyzed using ANOVA.
Results:
Results showed that serum levels of testosterone in the experimental groups 2 (100 mg) and 3
(200 mg) compared to the control group decreased significantly (P<0.05). Also, serum levels of
LH and FSH hormones in the experimental group decreased as compared with the control group.
Conclusion:
According to the results of this study, aloe vera plant’s alcoholic extract taken orally can decrease
testosterone and gonadotropin secretion in the male rats.
Keywords: Aloe Vera, Testosterone, Gonadotropin, Plants, Extracts
Introduction
Rapid growth of population poses a threat
in the modern world, especially in
developing countries. Given the limited
amount of resources, the population cannot
grow at the current pace for a long time.
On the other hand, reducing the number of
unplanned pregnancies may have a
positive effect on welfare, population
growth pattern and socioeconomic
development of a country. Previous studies
indicate that some 65% of unplanned
pregnancies may be blamed on failure of
contraception techniques [1]. In Iran, 18%
of pregnancies are unwanted and modern
contraceptive methods do not have an
*
Corresponding author, Address: Medical Science University, Mothahari Ave, Jahrom, Iran
Tel: 0791 3340406-10 E-mail: [email protected]
1
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Effect of alcoholic extract of aloe
appropriate coverage. In a physically and
mentally sane society, individuals are the
primary decision makers of pregnancy and
contraceptive techniques must be fully
successful. Illegal abortions constitute
another adverse complication of unplanned
pregnancies. Each year, about 68 thousand
women lose their life to unsafe abortion in
developing countries [2]. Considering the
lower risks associated with herbal
medications compared to their chemically
synthesized counterparts, it seems
reasonable to identify and promote the use
of medicinal plants.
Aloe vera belongs to the order of
Aspargales, family of Xanthorrhoeaceae
and subfamily of Asphodeloideae. It has
over 250 known species worldwide.
Botanically, it is a succulent plant with
spear-shaped, serrated leaves. It usually
grows to be 60 cm tall with a short wooden
stalk. The leaves, which attach directly to
the stem, are fleshy with a convex external
surface and slightly concave internal
surface. The flowers are yellow and form a
closely packed cluster [3]. The plant
blossoms in fall. Aloe vera has been used
in traditional medicine for thousands of
years, used in treatment of skin conditions
and other diseases. The most important
compounds
include
anthraquinones
(aloein, aloe-emodin, coumaric acid),
polysaccharides,
glycoproteins,
prostaglandins, cholesterol, and fatty acids
such as campesterol [4-6].
Previous studies suggest antitoxic [7,8],
antitumoral, antimicrobial, and antioxidant
properties [9-13] for aloe vera. Moreover,
is improves wound healing and activity of
macrophages [14, 15].
One study dealing with aloe vera effects
on ovaries of pregnant rats indicated that
the plant increases the weight and
improves
vascularization
around
secondary follicles in rats. Moreover, it
suggested the effects of aloe vera to be
similar to those of estrogen and follicle
stimulating hormone [16].
A recent study dealing with the impact of
aloe
vera
on
testosterone
and
Karimi et al
gonadotropins in adult male rats indicated
that the hydroalcoholic extract has
antiandrogenic properties and may reduce
androgen-related parameters, including
tropin secretion, probably causing
oligospermia [17]. Considering the little
data regarding the impact of aloe vera and
its compounds (such as aloe-emodin and
coumaric acid) on the reproductive system,
it is possible that these compounds may
influence sex hormones. Therefore, we
undertook the present study to investigate
the impact of alcoholic extract of aloe vera
leaf on testosterone and gonadotropin in
male, adult rats.
Materials and Methods:
In this study, we used 45 adult, male
Wistar rats. The mean weight of the rats on
onset of the study was 200 ± 20 g and they
were aged 2-3 months. The ambience
temperature was kept constantly at 25 ± 2
o
C throughout the study, and the rats had
unlimited access to compact food. The rats
were divided into 5 groups (each
comprising 9 rats) in the following
manner:
Control group: This group used water
and compact food ad libitum throughout
the study without any limitation.
Sham group: This group had unlimited
access to food and water throughout the
study, but received 2mm distilled water
orally simultaneously and similar to
experimental groups.
Experimental
groups:
Three
experimental groups were respectively
treated with 50, 100, and 200 mg/Kg body
weight of aloe vera extract via oral route.
The treatment continued for 30 days. At
the end of the 30th day, the rats were
anesthetized and blood samples were
drawn from their ventricles. The samples
were centrifuged at 3000 rpm for 10 min to
yield serums. Hormone quantification was
accomplished using radioimmunoassay.
The inclusion criteria were healthy male,
adult Wistar rats weighing 200 ± 20 g and
aged 2-3 months. Rats outside the age and
Journal of Jahrom University of Medical Sciences, Vol. 10, No. 2, Summer 2012
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Karimi et al
weight range were excluded from the
study.
Preparation of aloe vera extract:
The plant extract was prepared using the
standard soaking and percolation protocol
described by Fariba Abolhasantash [21].
For this purpose, 500 g fresh, chopped
leaves of the plant was soaked for 48 hours
in a vessel containing 96% ethanol. The
filtered solution was then centrifuged at
3000 rpm for 5 minutes to ensure the
removal of suspending particles. The
powder was prepared using a desiccator.
The resulting dry powder was dissolved in
distilled water at different amounts of 50,
100, and 200 mg. The volume of distilled
water was 2mL for all doses of powder.
Hormone quantification:
Levels of testosterone and gonadotropins
(follicle stimulating, follicle releasing)
were
determined
through
radioimmunoassay. For this purpose,
blood serum containing unlabeled antigen
is mixed with antigen labeled with iodine
125. Both antigens compete for binding to
the standard labeled antibody which is
added to the solution. The antibody is
initially bound to the unlabeled antigen
and the rest will bind with the labeled
antigen. The supernatant, containing free
labeled antigen and bound unlabeled
antigen is disposed and only the labeled
antigen bound with the antibody remains
as deposit, which is then evaluated with a
gamma counter.
Data analysis:
Data were analyzed on SPSS software
using one-way analysis of variance. P
values < 0.05 were considered significant.
Results
The following tables and diagrams present
the results of comparing testosterone and
gonadotropin levels among control, sham
and experimental groups.
Our findings indicate that the serum level
of testosterone in the experimental groups
2 and 3 was significantly lowered
compared to the control group (p<0.05). In
the first experimental group, however, the
serum level of testosterone was not
different from the control group (Diagram
1).
As for the follicle releasing hormone, our
results indicate that the serum levels of this
hormone was reduced at doses of 50, 100,
and 200 mg/Kg aloe vera alcoholic extract;
the difference, however, was not
significant between the experimental,
control and sham groups (p<0.05)
(Diagram 2).
All three doses of aloe vera extract
reduced the serum levels of follicle
stimulating hormone; nevertheless, the
reduction was not significant between
experimental, control and sham groups
(p<0.05) (Diagram 3).
Series 1
Dose 50: 7.71
Series 1
Control, 7.37
Testosterone Level (ng/mL)
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Effect of alcoholic extract of aloe
Series 1
Sham, 5.35
Series 1
Dose 200: 2.62
Series 1
Dose 100: 1.39
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Effect of alcoholic extract of aloe
Karimi et al
Diagram 1: Comparing the effect of different concentrations of aloe vera alcoholic extract on mean serum level
of testosterone among control, sham and experimental groups of male rats at the end of 30 th day
Series 1
Sham, 0.34
Series 1
Dose 50: 0.27
LH Level (ng/mL)
Series 1
Dose 100: 0.23
Series 1
Dose 200: 0.226
Diagram 2: Comparing the effect of different concentrations of aloe vera alcoholic extract on mean serum level
of luteinizing hormone among control, sham and experimental groups of male rats at the end of 30 th day
Series 1
Control, 0.28
FSH Level (ng/mL)
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Series 1
Control, 0.37
Series 1
Sham, 0.27
Series 1
Dose 50: 0.22
Series 1
Dose 100: 0.2
Series 1
Dose 200: 0.16
Diagram 3: Comparing the effect of different concentrations of aloe vera alcoholic extract on mean serum level
of follicle stimulating hormone among control, sham and experimental groups of male rats at the end of 30 th day
Table 1: Comparing the mean serum levels of testosterone and gonadotropins among groups treated with
different doses of aloe vera alcoholic extract and control in male adult rats at the end of 30 th day
Groups
Mean Testosterone
Mean LH
Mean FSH
Control
7.37 ± 4.37
0.37 ± 0.103
0.28 ± 0.192
Sham
5.35 ± 2.16
0.34 ± 0.11
0.27 ± 0.09
Dose 50
7.71 ± 6.18
0.27 ± 0.646
0.22 ± 0.119
Dose 100
1.39 ± 0.32*
0.23 ± 0.060
0.20 ± 0.173
Dose 200
2.62 ± 0.82*
0.22 ± 0.123
0.16 ± 0.188
* indicates significance compared to the control group (p<0.05)
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Discussion
In the present study, we observed that aloe
vera extract significantly reduced the level
of testosterone at doses of 100 and 200
mg/Kg body weight (p<0.05) (Diagram 1).
This is consistent with findings of Shariati
et al [17]. Recent studies indicate that
certain compounds in aloe vera, e.g.
coumaric acid, may stimulate the activity
of testicular macrophages which are
responsible for nitrous oxide production,
and suppress the conversion of cholesterol
to pregnenolone through inhibition of p450
cytochrome activity, thus reducing
testosterone secretion [18].
Studies conducted on the impact of
phytoestrogens on testosterone in rats
indicate that phytoestrogens lower the
serum concentration of testosterone [19]. It
is possible that aloe vera flavones exert
their effect through binding with hormone
receptors or hormone metabolizing
enzymes, similar to other phytoestrogenic
compounds [20]. On the other hand, it
appears that the impact of flavonoids on
hormone metabolizing enzymes, including
type 5 human 17 β-hydroxysteroid
hydrogenase is particularly important. This
enzyme constitutes a link in the
testosterone production pathway and is
suppressed by phytoestrogens [21].
Considering the results of previous studies
which suggest the presence of isoflavones
in aloe vera, it seems that the lowering of
testosterone level may be attributed to
these
phytoestrogenic
compounds.
Previous studies indicate that the
compounds present in aloe vera interfere
with androgen production and lower the
levels of testosterone and follicular
stimulating hormone [17].
Studies indicate that phytoestrogens affect
the hypothalamus to suppress the
production of gonadotropin releasing
hormone,
thus
inhibiting
the
hypothalamus-pituitary-gonad axis [22].
The gonadotropin releasing hormone
secreted from hypothalamus affects the
anterior pituitary to stimulate the secretion
of FSH and LH. The latter affects Sertoli
cells to promote the production and
secretion of androgen binding protein [17].
A reduction on LH levels will suppress the
activity of androgen binding protein,
lowering the estradiol levels.
The findings of the present study indicate
that aloe ver extract lowers the serum level
of FSH in experimental groups, although
the reduction was not significant (Diagram
3). Shariati et al demonstrated that the
hydroalcoholic aloe vera extract at 100 and
150 mg/Kg body weight lowers the serum
level of FSH significantly compared to the
control group [17]. The discrepancy may
be attributed to the difference in duration
of treatment and type of extract. In the
study mentioned above, the extract was
administered for 21 days, while we used a
treatment period of 30 days. On the other
hand, we used the ready powder of the
plant, while Shariati et al used aloe vera
gel [17].
In the present study, serum levels of LH
were lowered in the experimental group
compared to the control group, albeit the
difference was not significant (Diagram 2).
We expected the levels of LH to rise via
negative feedback due to testosterone
reduction, however, the presence of active
compounds in the extract, including aloe
emodin, may have directly affected
gonadotropins to reduce LH [20]. Other
potential
mechanisms
include
the
downgrading of LH receptors or reduced
sensitivity of these receptors. A reduction
in the number of these receptors on Lydig
cells in testes will compromise the
synthesis and secretion of testosterone.
Shariati et al studied the impact of aloe
vera extract on serum levels of LH, FSH
and testosterone. They did not find a
significant change in LH levels, which is
in line with our findings [17]. It is possible
that the feedback-based mechanism of LH
secretion from pituitary in reaction to
testosterone reduction requires a period
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Effect of alcoholic extract of aloe
longer than 30 days [17]. Roberts et al
(2000) demonstrated a lowering of LH
levels in rats exposed to genistein – a
phytoestrogens [23]. McGravey et al
studied the impact of a diet rich in
phytoestrogens on humans and animals to
conclude that campesterol suppresses the
secretion of LH, while genistein has no
such effect [24]. Previous studies indicate
that aloe vera increases the number of
secondary follicles, reduces their size and
improves their vascularity in the ovaries of
pregnant rats. The development of antral
(secondary) follicle is largely dependent
on FSH and aloe vera exerts an effect
similar to that of FSH in female rats. These
are all similar to the effects of estrogen on
genitalia [16]. Given the little data
available regarding the biologic impacts of
aloe vera extract on the reproductive
Karimi et al
system, it is extremely difficult to interpret
its
impact
on
testosterone
and
gonadotropin levels.
Conclusion
Considering the findings of the present
study, the alcoholic extract of aloe vera
generally reduces testosterone and
gonadotropin levels in male rats. Further
studies are recommended to address the
possible applications of this plant in
regulating fertility in the male sex.
Acknowledgement
The authors wish to express their gratitude
to the officials at vivarium of Shiraz
University of Medical Sciences, as well as
Dr. Azarpira and Mr. Bazrafshan who
collaborated in this study.
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