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Research Article
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Evaluation of Effect of Dietary Supplementation with Dacryodes edulis
G.Don Pulp Oil on Serum Lipid Parameters in Wistar Albino Rats |
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C.N. Ezekwesili
and
F.U. Eneh
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ABSTRACT
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The pulp of Dacryodes edulis G.Don which is rich in
oils is commonly consumed in Nigeria when in season. The effect of diet supplementation
with edulis fruit pulp oil on body lipid parameters was evaluated in male wistar
albino rats. D. edulis oil was extracted in n-hexane. The test diet was
compounded using the oil extract (10%), whereas the control animals were kept
on control diet formulated with groundnut oil (10%). After six weeks, the animals
were anaesthetized with chloroform and blood samples collected through cardiac
puncture for the determination of serum lipid profile. Results revealed that
D. edulis fruit pulp oil did not cause any significant (p>0.05) alterations
in serum total cholesterol, LDL-cholesterol and triacylglycerol. The total amount
of lipids present in the serum was increased by 33.3%, whereas the quantity
of liver lipids decreased by the same factor (33.3%). Insignificant (p>0.05)
increases in the weights (g 100 g-1 BW) of the liver (2.91±0.17
to 3.38±0.25), kidney (0.36±0.06 to 0.40±0.02) and heart
(0.32±0.02 to 0.33±0.04) were observed in the test group. No significant
change (p>0.05) in the average body weight of the test animals was recorded.
HPLC analysis of D. edulis oil showed that it contained palmitic acid
(48.7%), linoleic acid (28.6%),oleic acid (12.9%), stearic acid (5.0%), lauric
acid (2.2%), linolenic acid (1.7%) and myristic acid (0.9%). The peroxide value
of the oil was 0.00. Prolonged intake of D. edulis fruit pulp oil may
induce adverse effects on the body organs, even though the body lipid profile
remains unaltered.
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Received: May 09, 2013;
Accepted: January 16, 2014;
Published: February 12, 2014
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INTRODUCTION
The African pear (Dacryodes edulis G. Don) fruit is one amongst the
many indigenous tropical fruits greatly cherished and appreciated for its pulp.
The plant belongs to the Burseraceae family and possesses many medicinal and
nutritional properties. In Nigeria, when is season, the fruit pulp which is
contained in a pod is traditionally consumed raw or after tenderization in hot
water, hot ash or roasted (Isaac and Ekpa, 2009). Sometimes,
it may be enjoyed with roasted or boiled corn (Iyawe et
al., 2007).
Several studies have focused on the chemical composition of the D. edulis
fruit pulp. The percentage fatty acid composition of the lipid yield includes
palmitic acid (30- 62), linoleic acid (15-24), oleic acid (18-60), stearic acid
(1.3-5.5) depending on the geographical location of the tree (Mbofung
et al., 2002; Kinkela et al., 2006;
Ikhuoria and Maliki, 2007; Ajibesin,
2011). Nutritionally important mineral elements such as phosphorus, sodium,
zinc and manganese are also found in Eastern Nigeria varieties (Ajayi
and Adesanwo, 2009). The essential oils of the pulp as reported by Jitrovetz
et al. (2004); included x-pipene, β-pipene and myrcene. Bioactive
compounds such as saponins, tannins, alkaloids and flavonoids have been identified
in various parts of the plant (Okwu and Nnamdi, 2008)
and these have been suggested to be responsible for the enormous ethno-medical
applications of D. edulis in the treatment of skin diseases, inflammation,
bacterial and fungal infections (Okwu and Nnamdi, 2008;
Ajibesin, 2011).
The implication of high total cholesterol, Low-Density-Lipoprotein (LDL)-cholesterol,
triacylglycerol and low High-Density Lipoprotein (HDL)-cholesterol in the development
of cardiovascular disorders such as hypertension, artheriosclerosis, stroke
and heart failure can never be over emphasized (Ghasi et
al., 2000). There has been tremendous increase in the use of functional
foods and, or nutraceuticals due to their beneficial effects on human health.
For instance, cardiovascular activity of D. edulis oil in rats was reported
by Ajibesin (2011). Oil extracted from prickly pear
seeds oil has been found to exhibit hypoglycaemic and hypocholesterolemic effects
(Ennouri et al., 2007). Changes in the lipoprotein
composition of the plasma or serum could be attributed to the type of fat ingested
in the diet. The present study was therefore designed to investigate the effect
of continuous dietary intake of D. edulis fruit pulp oil (DFPO) extracted
in n-hexane on serum lipid parameters of Wistar albino rats (Ratus norvegicus).
MATERIALS AND METHODS
Plant materials: Healthy African pear (D. edulis) fruits were
collected from Abagana, Anambra State, Nigeira, in January, 2011. They were
identified and authenticated of by Prof. R. Okigbo, of the Department of Botany,
Nnamdi Azikiwe University, Awka. Voucher specimen (herbarium No. N.A.U.H No
112) was prepared and deposited in the herbarium.
The fruits were washed and the fruit pulps separated from the seeds, air-dried
at room temperature, wrapped in polyethylene bags and stored in desiccators
until needed. The dried fruit pulp was later pulverized using a grinding machine.
Three hundred gram quantity of the sample was transferred into a thimble and
oil content extracted for 2 h using normal hexane in vacuo with soxhlet
apparatus. At the end of the extraction, the extracting solvent (n-hexane) was
evaporated using rotary evaporator leaving the concentrated oil sample which
was used for the experiments. The percentage oil yield was determined gravimetrically.
Animal materials: Sixteen apparently healthy Wistar albino rats weighing
between 100.0 to 120.0 g were purchased from the Faculty of Veterinary Medicine,
University of Nigeria, Nsukka. The animals were kept in cages in the animal
house of the Department of Applied Biochemistry, Nnamdi Azikiwe University,
Awka, for one week to allow for acclimatization.
Chemicals used: Analytical chemicals were used and all were products
of British Drug House (BDH), Poole England. Triacylglycerol total cholesterol,
LDL-cholesterol and HDL-cholesterol diagnostic Kits were obtained from Randox
Laboratories Ltd., Ardmore, U.K.
Experimentation: The animals were divided into two groups of eight rats
each in accordance with their weights and housed in separate cages.
The first group was fed with the control diet compounded with 10% groundnut
oil, whereas the second group of rats was kept on the test diet compounded with
10% D. edulis fruit pulp oil. The chemical compositions of both diets
were as illustrated in Table 1. The body weights of animals
and feed intake were recorded at two days interval for a period of six weeks.
The daily feed intake was calculated using the equation:
where, Da is the amount placed in the bin feed and Db is the amount remaining
after 2 days. 8 corresponds to the number of animals in each cage.
All the animals were allowed free access to feed and drinkable water ad
libitum.
At the expiration of six weeks period of feeding, the animals were anaesthetized
with chloroform and blood samples collected through cardiac puncture for the
determination of serum lipid profile. The sera samples were obtained as the
supernatant after centrifuging the coagulated blood samples at 3,000 r.p.m for
15 min. Serum total cholesterol, LDL-cholesterol, HDL-cholesterol and triacylglycerol
levels were determined using diagnostic kits from Randox Laboratories, U.K.
Lipid extraction from serum and liver: The total lipids of sera samples
(500 μL) and liver (2 g) were extracted with chloroform: methanol (2:1,
v/v) according to the method of Folch et al. (1957).
The quantities of total lipids in the sera and liver samples were measured gravimetrically
after evaporating the extracting solvent in the sera and liver extracts.
Physicochemical studies: The physicochemical properties of the DFPO
were determined immediately by the AOAC (1975).
Fatty acid composition of the oil: Fatty acid profile of the oil was
obtained using a high-performance-liquid chromatographic technique (HPLC).
Proximate composition of the diets: The proximate composition of both
control and test diets were determined using the method of AOAC
(1984).
Statistical analysis: Arithmetic mean and standard error of mean were
calculated and all the data obtained were analyzed statistically using Analysis
of Variance (ANOVA). Statistical analyses were made by a SPSS for Windows version
13.0 packaged statistics program. All results represented were Mean+Standard
Error of mean (SEM) of six determinations.
RESULTS AND DISCUSSION
Findings from our study showed that Dacryodes edulis (G.Don) pulp yielded
a pale yellow oil (26.4±0.81% yield) with an agreeable odour. The oil
existed in the semisolid state at laboratory temperature of 29°C. The percentage
oil yield of 26.4 indicates that the pulp is a rich source of lipids. This is
comparable to other reports by Lam et al. (1987)
and Ajibesin (2011). Supplementation of DFPO (10%) into
the diet did not cause any significant difference in body weight gain between
the control and the test groups since the p. value (0.11) was greater than 0.05.
The average body weight increased from 183.51±2.3 g to 190.47±0.6
g after six weeks of feeding (Table 2).
The type of lipids ingested in the diet could provoke the deposition of fats
in the body tissues and for this reason we also estimated the total quantities
of extractable lipids in the serum and liver of the experimental animals. Insignificant
(p>0.05) variations in the amount of serum and liver lipids were observed
after the six weeks duration of feeding. Also, the relative weights of the vital
organs (the liver, pancreas, kidney and heart) were not statistically different
irrespective of whether the animals were fed with groundnut oil or DFPO (Table
2). Slight but insignificant (p>0.05) increases in the weights (g 100
g-1 BW) of the liver (2.91±0.17 to 3.38±0.25), kidney (0.36±0.06
to 0.40±0.02) and heart (0.32±0.02 to 0.33±0.04) were observed in the test group.
This implies that accumulation of lipids in these organs, particularly the liver
which plays a pivotal role in lipid metabolism, as a result of the supplementation
of the diet with DFPO was negligible.
Also supporting the above inferences is the fact that supplementation of the
diet with DFPO did not produce any remarkable alterations in the serum total-cholesterol,
LDL-cholesterol, HDL-cholesterol, VLDL-cholesterol and triacylglycerol levels
of the animals (Table 3). All the observed values were within
the normal ranges for total cholesterol (g L-1) (0.69±0.07),
LDL-cholesterol (g L-1) (0.21±0.03), HDL-cholesterol(g L-1)
(0.37±0.05) and triacylglycerols (g L-1) (0.56±0.07)
in the serum of adult albino rats (Alonso et al.,
2001; Gaiva et al., 2003).
Table 2: |
Body weights, feed intakes and relative weights of some vital
organs after six weeks of feeding in control and DFPO groups |
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Each value represents the mean of eight rats±standard error
of mean. No significant difference between groups was noted. p>0.05,
DFPO Dacryodes edulis fruit pulp oil |
Table 3: |
Serum lipid profile of rats fed control and DFPO diets |
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Values are Mean±SEM of eight observations. No significant
difference between groups was found at 95% level of significance. p>0.05
for all figures in the same row, *Atherogenic index (A.I) = Total cholesterol-HDL-cholesterol,
HDL-cholesterol, Deguchi and Ogata (1991), DFPO
Dacryodes edulis fruit pulp oil |
Table 4: |
Chemical properties of DFPO extracted with n-hexane |
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Values are Mean±SEM of eight observations, DFPO Dacryodes
edulis fruit pulp oil |
Table 4 shows the chemical properties of the D. edulis
fruit pulp oil. Acid value is a parameter that is used to indicate the suitability
of oil for consumption. The acid value of DFPO was 18.51"2.38. This is similar
to that of the conventional palm kernel oil, 14.04±0.022 (Akubugwo
and Ugbogu, 2007; Igbum et al., 2012) and
Landolphia owariensis, 15±0.38. (Pearson, 1976).
High iodine value of 50.32±0.63 observed in this study is a clear indication
of high level of unsaturation of the fatty acid components of DFPO. High-performance-liquid
chromatographic (HPLC) analysis of the oil also revealed the presence of appreciable
quantities of oleic acid (12. 94%) and linoleic acid (28.57%). Omega-3 fatty
acid, linolenic acid (1. 65%) was also detected (Table 5).
The health benefits associated with the consumption of oleic acid (18:1), linoleic
acid (18:2) and linolenic acid (18:3) have been well documented (Ennouri
et al., 2007, 2005; Chattopadhyay
and Bandyopadhyay, 2005; Ezekwesili et al.,
2010). particularly in alleviating cardiovascular, inflammatory and autoimmune
disorders.
Table 5: |
Fatty acid profile of DFPO extracted in n-hexane as given
by HPLC |
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DFPO Dacryodes edulis fruit pulp oil |
However, since the iodine value is also a parameter that indicates the capacity
of the oil to go rancid (Amoo et al., 2004),
adequate protection should be ensured during storage of DFPO in order to prevent
lipid peroxidation.
The peroxide value serves as an index to assess the deterioration of oils.
Freshly prepared oils usually have values that are equal to or less than 10,
whereas higher ranges (20-40) indicate rancidity of the oils (Akubugwo
and Ugbogu, 2007). The peroxide value of DFPO was 0.00. This may suggest
that DFPO have antioxidants that resist rancidity by preventing lipid peroxidation.
The iodine value and fatty acid profile of DFPO are very similar to those found
in the conventional oil palm oil (from Elais guineensis variety). The
oil contains approximately equal amounts of saturated (50.85%) and unsaturated
(49.14%) fatty acids Lam et al. (1987).
CONCLUSION
Data obtained from this study demonstrated that Dacryodes edulis (G.
Don) fruit pulp is a high oil-yield fruit producing nutritionally, biochemically
and medicinally important oil. Supplementation of animal diet with this oil
did not cause any significant alteration in the serum lipid profile of the experimental
animals.
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