Hypocholesterolaemic Effect of Aqueous Extract of Acalypha
wilkesiana ‘Godseffiana’
Muell Arg on Rats Fed Egg Yolk Supplemented Diet:
Implications for Cardiovascular Risk Management.
Ikewuchi Jude C.* and Ikewuchi
Catherine C.
Department of
Biochemistry, Faculty of Science, University of Port Harcourt, P.M.B. 5323, Choba, Nigeria
ABSTRACT:
The effect of
aqueous extract of Acalypha wilkesiana on the mean daily weight gain, lipid profile
and atherogenic indices of rats fed egg yolk
supplemented diets was investigated. The control group was given normal feed while
other three groups received 50g egg yolk/kg feed. The extract was orally administered daily at 200 and 250mg/kg body
weight; while the test control and control groups received appropriate volumes
of water by the same route. The mean daily weight gain of the test groups were
each significantly lower than the control, but not significantly different from
the test control. The plasma total, LDL and non-HDL cholesterol levels of the
test groups were each significantly less than the control and test control. The cardiac risk ratio and atherogenic coefficient of the test groups were each
significantly (P<0.05) lower than those of the test control, but not
different from the control. These results indicate a hypocholesterolaemic
effect of the extract, thus suggesting a likely protective role of the extract
against the development of cardiovascular diseases.
KEYWORDS: Acalypha wilkesiana, atherogenic indices, lipid profile, weight
control.
INTRODUCTION:
Dyslipidemia is one of the major
risk factors for the development of cardiovascular disease, and is often found,
associated with hypertension, diabetes mellitus and obesity1-4. Dyslipidemia
usually involve elevated plasma levels of triglycerides, total, LDL and VLDL
cholesterol and a low level of HDL cholesterol1-4. Therefore, any nutritional and pharmacologic
intervention that improves or normalizes abnormal lipid metabolism may be
useful for reducing the risk of cardiovascular diseases1,4.
Several drugs are at present, available for the management of dyslipidemia. However, there is renewed interest in the use
of herbal products.
Acalypha wilkesiana Muell Arg (family Euphorbiaceae) is a
popular outdoor plant that provides color throughout the year, although it is
also grown indoors as a container plant. Many cultivars are available with
different leaf forms and colors: A. wilkesiana ‘Godseffiana’ has
narrow, drooping, green leaves with creamy-white margins, 'Marginata'
has coppery-green leaves with pink or crimson margins, 'Macrophylla'
has larger leaves, variegated with bronze, cream, yellow and red, while 'Musaica' has green leaves that are mottled with orange and
red5,6. In
traditional medicine, the leaves of this plant are eaten as vegetables in the
management of hypertension, consequent upon which we undertook a study of the
effect of the plant leaves on: plasma sodium and potassium levels of normal
rabbits7; urinary and plasma chemistry8, blood pressure
and aorta contractility9, tissue profiles of ATPase
activity10 and enzymes of
energy metabolism11, of salt-loaded rats.
In the present study, the effect of aqueous
extract of the leaves on weight, plasma lipid profile and atherogenic
indices was investigated in rats fed egg yolk supplemented diet, with a view to
unveiling any likely cardioprotective potential.
MATERIAL AND METHODS:
Collection of Animals and Preparation of
Plant Extract: Albino
rats were collected from the animal house of the Department of Physiology,
University of Nigeria, Enugu Campus, Enugu, Nigeria.
Samples of the fresh Acalypha wilkesiana
plants were collected from within the Choba and Abuja
Campuses of University of Port Harcourt, Port Harcourt, Nigeria. After due
identification at the University of Port Harcourt Herbarium, Port Harcourt,
Nigeria, they were rid of dirt and the leaves were removed, oven dried at 550C
and ground into powder. The resultant powder was soaked in boiled distilled
water for 12h, after which the resultant mixture was filtered and the filtrate,
hereinafter referred to as the aqueous extract was stored for subsequent use. A
known volume of this extract was evaporated to dryness, and the weight of the
residue used to determine the concentration of the filtrate, which was in turn
used to determine the dose of administration of the extract to the test animals.
Experimental
Design: Studies
were conducted in compliance with applicable laws and regulations. The rats
were randomly sorted into four groups of five animals each, so that the average
weight difference was ±1.4g. The animals
were housed in plastic metabolic cages. After a one-week acclimatization period
on guinea growers mash (Port Harcourt Flour Mills, Port Harcourt, Nigeria), the
treatment commenced and lasted for two-weeks.
The control group was given normal feed while the three test groups
received 50g egg yolk/kg feed. The first test group (Test 1) received daily by
intra-gastric gavages 200mg/kg body weight of the Acalypha
wilkesiana extract; the second group (Test 2)
received 250mg/kg body weight of the Acalypha
wilkesiana extract; while the third group (test control) and the
control group received appropriate volumes of water by the same route. The two
weeks egg yolk supplementation is a modification of the two weeks 5% loading
reported by Agbafor and Akubugwo12. The
animals were allowed food and water ad libitum.
They were exposed to 12 hour light-dark cycle and were handled according to
standard protocol. At the end of the treatment period the rats were weighed,
fasted overnight and anaesthetized by exposure to chloroform. While under
anesthesia, they were painlessly sacrificed and blood was collected from each
rat into heparin sample bottles. Whole blood was immediately used to determine
the triglyceride levels (using test strips), while the heparin anti-coagulated
blood samples were centrifuged at 1000g for 10min, after which their plasma was
collected and stored for subsequent analysis.
Determination of the Plasma Lipid
Profiles/Indices: Plasma triglyceride
concentration (TG) was determined using multiCareinTM triglyceride strips
and glucometer (Biochemical Systems International,
Arezzo, Italy). The test is based on lipase/glycerol kinase/glycerol
phosphate oxidase/peroxidase/chromogen reaction. The intensity of the colour developed from the reaction is proportional to the
concentration of triglycerides in the blood. Plasma total (TC) and high density
lipoprotein (HDLC)
cholesterol concentration were assayed enzymatically with Randox commercial test kits (Randox
Laboratories, Crumlin, England). In the presence of
magnesium ions, low density lipoproteins (LDL and VLDL) and chylomicrons
fractions are precipitated quantitatively by the addition of phosphotungstic acid. After centrifugation, the cholesterol
concentration of the high density lipoprotein (HDL) fraction, which remains in
the supernatant, can be determined, as in total cholesterol. The cholesterol
released by enzymatic hydrolysis is oxidized with the concomitant release of
hydrogen peroxide, whose breakdown leads to the conversion of
4-aminoantipyridine to quinoneimine (the indicator) whose
concentration can be determined spectrophotometrically at 500nm.
Plasma VLDL- and LDL-cholesterol (LDLC and
VLDLC) concentrations
was calculated using the Friedewald equation13
as follows:
· [LDL cholesterol] (mg/dL) = [Total cholesterol] – [HDL cholesterol] – [Triglyceride]
5
· [VLDL
cholesterol] (mg/dL)
= [Triglyceride]
5
While the plasma
non-HDL cholesterol concentration was determined as reported by Brunzell et al.14:
· [Non-HDL
cholesterol] = [Total cholesterol] – [HDL cholesterol]
The atherogenic
indices were calculated as earlier reported by Ikewuchi
and Ikewuchi15 using the following formulae:
· Cardiac
Risk Ratio (CRR) = [Total
Cholesterol]
[HDL
Cholesterol]
· Atherogenic Coefficient (AC) =
[Total
Cholesterol] - [HDL Cholesterol]
[HDL
Cholesterol]
· Atherogenic Index of Plasma
(AIP) =
log
[Triglyceride]
[HDL Cholesterol]
Statistical
Analysis of Data: All values are quoted
as the mean ± SEM. The values of the various parameters for all the groups were
analyzed for statistical significant differences using the student’s t-test,
with the help of SPSS Statistics 17.0 package. P<0.05 was considered to
significant.
Table 1 Effects of aqueous extract of Acalypha wilkesiana on
the daily weight gain and plasma lipid profile of rats fed egg yolk
supplemented diet
Values are mean ± SEM, n=5, per group. Values in the same row with the different
superscripts are significantly different at P<0.05.
Table2: Effect of aqueous extract of Acalypha wilkesiana on
atherogenic indices of rats fed egg yolk supplemented
diet.
|
Index |
Magnitude |
|||
|
Control |
Test control |
Test 1 |
Test 2 |
|
|
Cardiac
risk ratio Atherogenic coefficient Atherogenic index of plasma |
3.110±0.096a 2.110±0.096a -0.616±0.059a |
7.15±0.990b 6.15±0.990b -0.318±0.074b |
3.457±0.793a 2.457±0.793a -0.511±0.052a,b |
5.505±0.633a 4.505±0.633a -0.139±0.120a,b |
Values are mean ± SEM, n=5, per group. Values in the same row with the different
superscripts are significantly different at P<0.05.
RESULTS:
The effects of
aqueous extract of Acalypha wilkesiana on the daily weight gain and plasma lipid
profile of rats fed egg yolk supplemented diet is given in Table 1. The mean
daily weight gain of the test groups were each significantly lower than the
control, but not significantly different from the test control. The plasma
triglyceride and VLDL cholesterol levels of the test groups were not
significantly (P<0.05) different from the control and test control. The
plasma total, LDL and non-HDL cholesterol levels of the test groups were each
significantly less than the control and test control. The effects seem to be
dose dependent, with the 200mg/kg body weight dose being more effective.
Table 2 shows the
effect of aqueous extract of A. wilkesiana on
the atherogenic indices of rats fed egg yolk
supplemented diet. The cardiac risk ratio and atherogenic
coefficient of the test groups were each significantly (P<0.05) lower than
those of the test control, but not different from the control. There were no
significant differences in the atherogenic index of
plasma of the three groups.
DISCUSSION:
The
effects of the extract was dose dependent, with the 200mg/kg dose being more
effective (Tables 1 and 2). The extract produced low plasma total cholesterol
levels in the treated rats. This may be cardioprotective,
since elevated plasma total cholesterol level is a recognized and
well-established risk factor for developing atherosclerosis and other
cardiovascular diseases16. This hypocholesterolaemic
activity of the extract may be due to its high saponin
content17. In human nutrition, saponins
are reported to assist in the prevention of cardiovascular diseases18
by lowering plasma cholesterol concentrations through the excretion of
cholesterol directly or indirectly as bile acids19-21.
Decreases in
plasma LDL cholesterol have been considered to reduce risk of coronary heart
disease3,4. In this study, a
significantly lower plasma LDL cholesterol level was produced by the extract,
indicating its likely cardio-protective potential. Several studies have shown
that non-HDL cholesterol is a better predictor of cardiovascular
disease risk than is LDL cholesterol14,22,23. Therefore, the significantly lower plasma non HDL cholesterols
observed in the test groups indicate the ability of the extract,
to reduce cardiovascular risk.
The atherogenic indices are strong indicators of the risk of
heart disease: the risk of developing cardiovascular disease increases with
increases in the values of these indices, and vice versa24-27. Low atherogenic indices are protective
against coronary heart disease26. In this study, the extract
produced significantly lower cardiac risk ratio and atherogenic
coefficient.
Finally, these results indicate a dose dependent hypocholesterolaemic effect of the extract, thus suggesting
a likely protective role of the extract against the development of
cardiovascular diseases.
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Received on 26.08.2010
Accepted on 19.09.2010
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2010:
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