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African Journal of Biotechnology Vol. 6 (8), pp. 1007-1011, 16 April 2007
Available online at http://www.academicjournals.org/AJB
ISSN 1684–5315 © 2007 Academic Journals
Full Length Research Paper
Effects of Persea americana leaf extracts on body
weight and liver lipids in rats fed hyperlipidaemic diet
B. I. C. Brai1, 2 *, A. A. Odetola2 and P. U. Agomo1
1Nigerian Institute of Medical Research, P. M. B. 2013, Yaba. Lagos, Nigeria.
2Department of Biochemistry, University of Ibadan, Ibadan, Nigeria.
Accepted 31 August, 2006
The effects of aqueous and methanolic leaf extracts of Persea americana on body weight and liver
lipids in rats were studied. Male albino rats were fed a modified diet containing 0.5% cholesterol and
0.25% cholic acid to provoke hyperlipidaemia. The hyperlipidaemic rats were given 10 mg/kg body
weight of either aqueous or methanolic extract of P. americana leaf daily for 8 weeks. There were no
significant differences (p>0.05) in the overall body weight gain of the hyperlipidaemic rats compared to
normal control. However, the administration of the aqueous and methanolic extracts provoked 14 and
25% reduction, respectively, in the body weight gain of the treated rats compared to the
hyperlipidaemic control. Mean liver weights were markedly increased (p<0.05) in rats fed
hyperlipidaemic diet (groups B, C and D: 70, 69 and 57%, respectively) compared to normal control rats.
The methanolic extract provoked a minimal (8%) decrease in mean liver weight compared to the
hyperlipidaemic control rats. It can be hypothesized that P. americana leaf extracts increase catabolism
of lipids accumulated in adipose tissue causing a decrease in body weight but does not influence liver
lipid levels in rats.
Key words: Persea Americana, body weight gain, hyperlipidaemia, leaf extracts, albino rats.
INTRODUCTION
Lifestyle changes accompanying industrialization have a
significant impact on the health of the people. The
modernization of societies appears to result in a dietary
pattern that is high in saturated fats and refined sugars
and is low in fibre content. Analyses of available
aggregate data sources indicate that a shift towards
“western diets” high in saturated fat and sugar and low in
fibre is occurring (Reddy and Yusuf, 1998; Popkin, 2002).
In Nigeria, there appears to be a cultural transition
towards a more westernized lifestyle. The traditional
foods consisting mainly of roots, cereals, beans, tubers
and vegetables are giving way to fatty foods, sweet
snacks and drinks which have too much calories. These
changes in dietary pattern among Nigerians, coupled with
*Corresponding authors E-mail: barthrem@yahoo.com. Tel:
234-803 333 9286. Fax: 234-1-342 5171.
changes in physical activity patterns, increased use of
tobacco products and alcohol are possible causes of
hyperlipidaemia and obesity which are becoming
important factors in the pathogenesis of chronic
degenerative diseases such as cardiovascular disease,
diabetes and cancer.
It has been postulated that in many individuals excess
weight gives rise to cardiovascular disease, type 2
diabetes mellitus, hypertension, stroke, dyslipidaemia,
osteoarthritis, and some cancers (Eckel et al., 2006;
Burton et al., 1985; Ezzati et al., 2005). It is also known
that fatty liver disease is associated with hyperlipidaemia
and obesity (Sharadi and Eldad, 2000). Plants were the
major source of materials which the ancient man resorted
to for combating various ailments and thus preserving his
health (Akah and Ekekwe, 1995). At present, a number of
botanicals are still being used in folk-medicine for
treatment of different diseases.
Persea americana (avocado or alligator pear) is an
almost evergreen tree belonging to the laurel family,
1008 Afr. J. Biotechnol.
Table 1. Mean weekly body weights of rats fed with extracts of P. americana.
Week A B C D
0 65.95 ± 3.46 65.88 ± 11.23 93.13 ± 9.62 87.37 ± 11.01
1 69.52 ± 7.80a 77.95 ± 13.89b 101.99 ± 12.30 b 95.64 ± 9.18 b
2 81.45 ± 6.93 85.12 ± 14.61 114.16 ± 14.24 108.10 ± 10.40
3 90.13 ± 8.64a 94.20 ± 17.34a 117.62 ± 15.12b 111.41 ± 10.4b
4 107.58 ± 9.59 a 97.19 ± 15.52b 124.20 ± 16.19b 112.89 ± 25.82 b
5 123.82 ± 9.46 115.24 ± 17.21 134.92 ± 19.99 124.45 ± 27.44
6 135.83 ± 6.84 125.27 ± 19.60 152.86 ± 24.72 141.53 ± 29.88
7 141.31 ± 7.37 135.60 ± 16.54 160.18 ± 24.65 150.55 ± 30.11
8 154.13 ± 9.50 a 152.59 ± 20.80 a 167.56 ± 25.74 b 152.35 ± 29.93 b
Values are expressed as means ± SD for six rats.
Values not sharing a common superscript letter differ significantly at p<0.05.
Group A, rats fed standard chow; Group B, rats fed modified diet; Group C, rats fed modified diet + 10 mg/kg body weight of
aqueous extract of P.americana; Group D, rats fed modified diet + 10 mg/kg body weight methanolic extract of P. americana.
Lauraceae. It is indigenous to Central and South America
but is now cultivated in the United States, Asia, parts of
Europe and tropical Africa. The leaves are alternate, dark
green and glossy on the upper surface, whitish on the
underside; variable in shape (lanceolate, elliptic, oval,
ovate or obovate) 7.5 – 40 cm long (Morton, 1987).
According to Morton (1987), avocado has many
medicinal uses. The leaves are chewed as a remedy for
pyorrhea. The aqueous extract of the leaves has a
prolonged antihypertensive effect. The leaf decoction is
taken as a remedy for diarrhea, sore throat and
haemorrhage. It allegedly stimulates and regulates
menstruation. Recently, the aqueous leaf extract of P.
Americana was reported to possess hypoglycemic
activity (Antia et al., 2005). The purpose of this study was
to test whether the leaf extract of P. americana would
influence body weight gain and liver lipid levels in a rat
model.
MATERIALS AND METHODS
Preparation of plant extracts
Fresh leaves of P. americana were obtained from a cultivated plant
in Lagos. The leaves were air-dried and pulverized in a Waring
blender and the aqueous and methanolic extracts prepared by
means of Soxhlet extraction. The extracts were evaporated to
dryness in an oven at 40°C and stored in clean sterile vials until
required.
Animal feeding
Albino rats were divided into four feeding groups (A, B, C and D) of
six rats per group. Group A was fed standard rat chow and water.
Groups B to D were fed a modified diet containing 20% groundnut
oil, 0.5% cholesterol and 0.25% cholic acid to provoke
hyperlipidaemia. In addition, groups C and D rats were orally
treated with aqueous and methanolic extracts of P. americana
respectively at a daily dose of 10 mg/kg body weight. Rats in group
B acted as hyperlipidaemic control and received water orally. The
animals were observed daily and weighed weekly for 2 months.
At the end of the feeding period, the animals were sacrificed under
pentobarbital anaesthesia (100 mg/kg body weight). The livers,
hearts, brains, kidneys and lungs were quickly excised and
perfused with chilled 1.15% (w/v) KCl solution in order to remove all
traces of contaminating haemoglobin. The tissues were blotted dry,
weighed and stored at −80oC pending analysis.
Determination of liver lipids
Liver lipids were extracted according to the method of Folch et al.
(1957). Liver total cholesterol (T-CHOL), high-density lipoproteins
(HDL-CHOL), low-density lipoproteins (LDL-CHOL), and
triacylglycerols (TAG) were measured using appropriate kits
supplied by RANDOX Laboratories Ltd., Crumlin, United Kingdom.
Statistical analysis
Data, expressed as mean ± S.D, were analyzed by analysis of
variance (ANOVA). Statistical significance of the difference of the
means was evaluated by Student’s t-test. Differences were
considered statistically significant if the p value was < 0.05.
RESULTS
Table 1 shows the mean weekly body weights of rats in
the four experimental groups. In the first week, body
weight increase was significantly higher (p<0.05) in the
hyperlipidaemic rats compared to normal control. Also,
there were significant differences (p<0.05) in body weight
increase in the 3rd, 4th and 8th weeks among the various
groups. Body weight increase in the second week was
least in hyperlipidaemic control rats. However, in the 3rd
and 8th weeks body weight increase was significantly
lower (p<0.05) in the treated groups compared to the
normal and hyperlipidaemic control rats.
However, there were no significant differences (p>0.05)
in the overall body weight gain and the overall weight
Brai et al. 1009
0
10
20
30
40
50
60
70
80
90
100
A B C D
Weight Gain (g)
Figure 1. Mean overall body weight gain in rats fed with extracts of P. americana. Values are
means ± SD (n = 6). Group A =fed standard rat chow; Group B =fed modified diet; Group C =fed
modified diet + 10 mg/kg body weight aqueous extract of P. americana; Group D = fed modified
diet + 10 mg/kg body weight of methanolic extract of P. americana.
0
1
2
3
4
5
6
7
8
A B C D
Liver Weight (g)
Figure 2. Mean liver weights in rats fed with extracts of P. americana. Values are means ± SD (n = 6).
Group A =fed standard rat chow; Group B =fed modified diet; Group C =fed modified diet + 10 mg/kg
body weight aqueous extract of P. americana; Group D = fed modified diet + 10 mg/kg body weight of
methanolic extract of P.americana.
gain per cent for groups A, B, C and D were 133.71,
131.62, 79.92 and 74.37, respectively. However rats
treated with both aqueous and methanolic P. americana
leaf extracts showed decrease in overall body weight
gain (14 and 25%, respectively) compared to the
hyperlipidaemic control (Figure 1).
Figure 2 shows the mean liver weights of rats in all the
groups. Liver weight was markedly increased (p<0.05) in
1010 Afr. J. Biotechnol.
Table 2. Mean weight of organs of rats fed with extracts of P. americana.
Organ A B C D
Kidney 0.93 ± 0.13 0.88 ± 0.09 0.83 ± 0.10 0.80 ± 0.14
Lungs 0.702 ± 0.07 0.72 ± 0.12 0.87 ± 0.11 0.90 ± 0.22
Heart 0.53 ± 0.14 0.53 ± 0.07 0.55 ± 0.07 0.55 ± 0.12
Brain 1.40 ± 0.12 1.42 ± 0.12 1.60 ± 0.08 1.57 ± 0.04
Values are expressed as means ± SD for six rats.
Group A, rats fed standard chow; Group B, rats fed modified diet; Group C, rats fed modified diet + 10 mg/kg body weight of
aqueous extract of P. americana; Group D, rats fed modified diet + 10 mg/kg body weight methanolic extract of P.
americana.
Table 3. Liver lipid profile (mg/dl) of rats fed with extracts of P. americana.
Lipid A B C D
T-CHOL 47.53 ± 8.56a 599.53 ± 97.97b 616.43 ± 56.81b 610.30 ± 39.47b
LDL-CHOL 35.15 ± 11.01a 415.36 ± 136.62b 415.54 ± 48.76b 416.28 ± 8.10b
HDL-CHOL 5.11 ± 2.11a 11.67 ± 3.73b 9.68 ± 5.71b
12.41 ± 3.93b
TAG 36.73 ± 10.05a 862.50 ± 207.43b 956.03 ± 280.68b 908.02 ± 192.48b
Values are expressed as means ± SD for six rats.
Values not sharing a common superscript letter differ significantly at p<0.05
Group A, rats fed standard chow; Group B, rats fed modified diet; Group C, rats fed modified diet + 10 mg/kg body weight of
aqueous extract of P.americana; Group D, rats fed modified diet + 10 mg/kg body weight methanolic extract of P.americana
rats fed the hyperlipidaemic diet (groups B, C and D: 70,
69 and 57%, respectively) compared to normal control
rats. Other organs did not show any significant difference
(p>0.05) in weight although brain weight was higher in
rats treated with P. americana leaf extracts compared to
normal and hyperlipidaemic control (Table 2). The liver
lipid profile of the rats in the four experimental groups is
shown in Table 3. Liver T-CHOL, LDL-CHOL and TAG
were significantly raised (p<0.05) in rats fed
hyperlipidaemic diet compared to normal control.
DISCUSSION
Throughout the period of experiment there was no
significant difference in food consumption in all groups
(data not shown). The body weights of rats in each group
were determined weekly as a general index of overall
health. Based on body weight, each group of rats
tolerated the treatment diet when compared with rats fed
standard chow. It is evident from our study that the
administration of aqueous and methanolic leaf extracts of
P. americana provoked a reduction in body weight gain
compared to the hyperlipidaemic control. It could be that
P. americana leaf extracts increase the catabolism of
lipids accumulated in adipose tissue resulting in a
decrease in mean body weight.
Liver weights were significantly increased by the intake
of hyperlipidaemic diet as compared to normal control
rats, and it was accompanied by significant increase in
liver cholesterol level. This result is in agreement with
previous report that liver weights were significantly
enhanced by intake of hyperlipidaemic diet containing 1%
cholesterol, 0.5% cholic acid and 25% coconut oil (Zulet
et al., 1999). It was observed that the excised livers of
rats fed hyperlipidaemic diet were golden yellow in
colour. This is similar to the findings that treatment with
poloxamer-407 to induce hypercholesterolemia result in
the development of golden yellow livers in C57BL/6 mice
(Palmer et al., 1998; Johnston et al., 1999).
There was a 13-fold increase in hepatic cholesterol
concentrations in the hyperlpidaemic rats compared to
control. A 2-fold increase in hepatic cholesterol had
previously been reported in rats relative to control when
both were fed a high-fat atherogenic diet containing
cholic acid (Shefer et al., 1992). Also, feeding diets
supplemented with cholesterol and cholic acid markedly
increased liver weights (two-fold), hepatic triglycerides
(3.7 fold) and cholesterol (12 fold) concentrations in
geese (Eder, 1999). Inclusion of saturated fatty acids in
the diet has been shown to produce
hypercholesterolemic effect in rats (Lutz et al., 1994;
Zulet et al., 1999). The groundnut oil included in the
hyperlipidaemic diet in this study contained 17%
saturated fatty acids and this could account for the
difference in increase in the accumulation of cholesterol
in the liver in this study. It is possible that the normal
catabolism of liver lipids was impaired in the rats fed
hyperlipidaemic diet with consequent accumulation of
lipids in the liver. The hepatic cholesterol concentrations
in the treated rats and the hyperlipidaemic control were
similar suggesting that both aqueous and methanolic leaf
extracts of P. americana at a concentration of 10 mg/kg
body weight used in this study could not exert
antihyperlipidaemic effect in the liver.
In conclusion, it can be hypothesized that P. americana
leaf extract increases catabolism of lipids accumulated in
adipose tissue causing a decrease in mean body weight
gain. However, it might be necessary to determine
whether higher concentrations of P. americana leaf
extract would reduce liver lipid levels in obesity and fatty
liver conditions.
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