III.1.6.4. Effect of
extracts on the activity of transaminases (ASAT, ALAT), creatinine and total
protein levels
A significant increase (p<0.05) in, the creatinine and
protein levels were observed in the positive control as compared to the
negative control. This translates abnormality in the functions of the kidney.
The activity of transaminase ASAT/ALAT was not significantly different between
negative and the positive control.
Table XXI: Effect of extracts on the activity of
transaminases (ASAT, ALAT), creatinine and total protein levels
|
Groups
|
ASAT (U/L)
|
ALAT (U/L)
|
Creatinine (mg/dl)
|
Proteins (g/l)
|
|
Negative control
|
87.532#177;0,977
|
33.406 #177;0.977
|
1.202#177;0,442
|
68.476#177;3.041
|
|
Positive control
|
91.529#177;3,316a
|
37.674#177;2,048a
|
2.877#177;0,468*a
|
83.258#177;3.419*a
|
|
Treated groups
|
|
FOHT(300mg/Kg)
|
80.025#177;2.419b
|
32.941#177;2.907a
|
0.647#177;0.576b
|
72.181#177;4.754b
|
|
FOHF(300mg/Kg)
|
90.598#177;2.882a
|
31.777#177;0.553a
|
1.017#177;0.379c
|
79.040#177;1.837a
|
*: significant difference between the positive control and
the negative control
a, b and c : significant difference at the threshold
0,05 between positive control and the test groups.
There was a significant decrease (p<0, 05) in the
concentration of creatinine in the test groups as compare to the positive
control. The concentration of ALAT and ASAT of the test groups was not
significantly different (p<0, 05) from that of the positive control.
In addition, the concentration of protein was significantly
(p<0,05) reduced in the test group FOHT as compared to the positive control
but there was no significant difference between the test group FOHF and the
positive control.
The above results enable us to suggest that our atherogenic
diet and high fructose-high cholesterol intake has a positive effect on the
induction of hyperlipidemia and CVD.
III.1.6.7. Effect of
extracts on nitric oxide level
From the figure below, we observed that nitric oxide level was
significantly (p<0, 05) reduced in the positive control as compared to the
negative control in the plasma but not the heart. This implies that the diet
has produced a positive effect in the endothelia dysfunction.
Figure 15 : Effect of extracts on nitric
oxide level in the plasma and heart
*: significant difference between the positive control and
the negative control
a and b : significant difference at the threshold 0,05
between positive control and the test groups
We also observed that at the level of the plasma, the positive
control was significant lower (p<0, 05) than in the test groups whereas at
the level of the heart the concentration of nitric oxide was not significantly
different between the positive control and the test groups
III.2.Discussion
The present study deals with two dimensions of the
antidiabetogenic effects of the plant extracts of F. ovata. In one
dimension, the hypoglycemic effect was measured. In the other dimension
hypolipidemic potential of this plant extracts was studied as there is a close
correlation between hyperglycemia and hyperlipidemia.
Preliminary, all four extracts screened for phytochemical,
revealed the presence of groups of bioactive compounds such as alcaloids,
glycosides, saponins, and polyphenolic compounds such as flavonoids, tannins
and phenols. Phlobatannins were absent in the fruit extracts of F.
ovata. These results correlate with that of Poongothai
(2011) whose investigation on the preliminary phytochemical screening
of Ficus racemosa linn bark reveal the presence of the above compound
and stated that they possess a variety of biological activity including
hypoglycaemia. Previous studies done on methanolic bark of F. ovata
extract reveal the presence of certain triterpenoids such as â
sitosterol, lupeol, and oleanolic acid (Kuate et al.,
2009) which are known to possess some antidiabetic activities..
Generally the polyphenolic content test and the DPPH
antiradical activity test showed that hydroethanolic extracts of fruits and
twigs had the best solvent system as compared to the ethanolic extracts for
each plant part. When comparing the total water soluble phenolic concentration
with the DPPH radical scavenging antioxidant activity of the fruits and twigs
extracts (table XIII and figure11), no positive correlation was observed. This
goes to support the hypothesis of Brand Williams et al.
(1995) that the DPPH kinetic is proportional to the amount of OH
group present on the phenolic compound (Claudia et al.,
2008). Thus, the hydroethanolic extracts may be rich in phenolic
coumpounds that have many OH groups leading to it high DPPH scavenging
activity. These compounds act as hydrogen donors to free radicals by stopping
lipid peroxidation at the stage of initiation (Claudia et al.,
2008).
Concerning acute toxicity, the extracts administsrated at a
unique dose of 5000mg/Kg lead to no deaths. Following the classification of
OECD (2001), which states that substances administstared at a
dose =5000mg/Kg of BW and that does not lead to a lethal effect, can be
presented as weakly toxic. This suggests that our extracts could be considered
as being weakly toxic.
In this study, we observed the inhibition of alpha amylase
activity by the hydroethanolic extracts with the fruits showing a high
inhibition profile as compared to the twigs. Also, concerning the hypoglycemic
test (BGT) in hyperglycemic rats, we did not observe a significant reduction of
glycemia between the control and the test groups throughout the 5 hours of
experiment. The percentage decrease on the blood glucose level of the
hydroethanolic twigs (8.908%) was higher than that of hydroethanolic fruits
(5.747%). The antihyperglycemia test done on normal rats showed that our
extracts have high lowering effect on glycemia 30 minutes after glucose loads
as compared to the positive control. From the 60th minutes to the
120th minutes, the glucose level was higher in the test groups than
the positive control. This may be due to the slow metabolism of glycosides
present in our plant that increases the blood glucose level. The percentage
decrease on the blood glucose level of the hydroethanolic twigs (21.566%) was
higher than that of hydroethanolic fruits (8.208%). This percentage decrease in
blood glucose in the hypoglycemic test and the improved glucose tolerance may
be due to various phytochemicals found to possess a wide range of activities,
which may help in protection against chronic diseases. For example, glycosides,
saponins, flavonoids, tannins and alkaloids have hypoglycemic activities; anti-
inflammatory activities. The terpenoids have also been shown to decrease blood
sugar level in animal studies (Poongothai, 2011). This made us
think that the hydroethanolic extract may act by stimulating the secretion of
insulin in beta cells of pancreas, increasing insulin sensitivity in addition
to inhibition of the alpha amylase activity and many other enzymes involved in
the transformation of dietary carbohydrate or glycogen to glucose. This
correlate with the study done by Tormo et al. (2004)
where after the administration of the polyphenolic extracts of fruits which had
presented a high inhibition of the alpha amylase activity in rats, showed a
lowering effect on the blood glucose of treated rats. This also correlates with
the work by Ortiz-Andrade et al. (2006) on
Glucosidase inhibitory activity of the methanolic extract from Tournefortia
hartwegiana where Pharmacological investigations, reported that
â-sitosterol induced the uptake of insulin from â-cells and
produced an anti-hyperglycemic effect. On the other hand, stigmasterol, lupeol,
ursolic and oleanolic acids showed to have hypoglycemic activity. Oleanolic
acid and semi-synthetic derivatives were described as â -glucosidase
inhibitors.
It is now well established that fructose feeding causes
insulin resistance in experimental animals. For this study the fasting blood
glucose at the end of experimentation was not significantly different between
the control groups and FOHT extract but that of the FOHF extract was
significantly lower than that of the positive control group. This could be
explained by the fact that the time of experimentation was not long enough to
result to insulin resistance or glucose intolerance as the glycemia after
experimentation for the positive control was less than 110mg/dl. This result is
contrary to that of Idowu et al. (2010) whose work on
the glycemic effect of Ficus exasperata in fructose induced
glucose intolerance and found that the extract ameliorated glucose intolerance.
Inspite of the absent of glucose intolerance, FOHF extract showed a blood
glucose lowering activity in vivo and this could be due to the fact that the
extracts may stimulate insulin secretion by the pancreas or/and enhance insulin
sensitivity in various organs especially the muscle and the live in a manner
similar to sulfonylureas.
The consumption of high fat diet by rats associated with
cholesterol and fructose throughout the sub acute experiment resulted in a
group of metabolic disorders which was felt at the level of some plasma
biochemical parameters in the absence of treatment. During the experimental
period, an increase in body weight variation was observed in the negative
control compared to positive control. This is contrary to the result obtained
by Raneva and Shimasaki (2005) who obtained the increase of
body weight in mice using high-fat diet during their study on the effects of
green tea catechins on lipid peroxidation on the organs of mice. In the treated
groups, the extracts FOHT and FOHF showed a significantly low weight variation.
Phytochemical Screening of the extracts revealed significant (p <0.05)
presence of polyphenols which could be involved in various mechanisms leading
to reduced energy reserves and thus reducing the variation of BW. They may
stimulate hepatic lipid metabolism and low accumulation of fatty acids in the
liver and visceral organs as shown by Murase et al.
(2002).
The results of lipid profile showed that the atherogenic diet,
high fructose-high cholesterols significantly increased (p<0.05) plasma
concentrations of total cholesterol, triglycerides and LDL cholesterol in the
positive control compared to negative control (Table XIX). These results are
comparable to those of Czerwinski et al. (2004) who
show increased consumption of dietary cholesterol resulted in a high
cholesterol, high triglyceride levels, high plasma lipid peroxides and
atherogenic index chol-LDL/chol-HDL. These high levels of LDL cholesterol in
the positive control could be attributed to their lack of recognition by their
receptors on the cell membrane. If LDL is not recognized by it receptors could
cause oxidation and endothelial dysfunction promoting leukocyte and platelet
adhesion and release of growth factors necessary for atherogenesis
(Lavoie, 2003). The treatment with the extract FOHF resulted
in a significant decrease (p <0.05) in plasma TC, triglycerides, VLDL and
LDL-cholesterol. But this decrease was not significant with the extract FOHT.
HDL-cholesterol concentration increased significantly with the administration
of the extract FOHF (Table XX). This improvement in lipid profile can be
explained by the presence of saponins in the extracts FOHF as shown by
Dhandapani (2007), working on the hypolipidemic activity of
extracts of Eclipta prostrata leaves in male albino rats of Wistar
strain. Reports show that saponins possess hypocholesterolemic and antidiabetic
properties. Increased atherogenicity indices TC / HDL-chol and
chol-LDL/chol-HDL was observed in rats of untreated group receiving the
atherogenic diet (positive control), which corroborates Dhandapani
(2007) which showed that consumption of high fat diet increased the
atherogenic index. The administration of the extract FOHF resulted in a
significant decrease (p <0.05) of these index with increase in the
protection against the development of atherosclerosis. Hyperlipidemia is
attributable to excess mobilization of fat from the adipose tissue due to the
under utilization of glucose (Mohana et al., 2010).
Regarding the mechanism of action saponins found in F ovata may
enhance the activity of enzymes involved in bile acid synthesis and its
excretion by precipitating cholesterol from micelles and interfere with
enterohepatic circulation of bile acids making it unavailable for intestinal
absorption (Santosh et al., 2009). Moreover, a
significant decline in plasma LDL-cholesterol in treated groups could be
correlated with saponin content of F. ovata, saponins may enhance the
hepatic LDL-receptor levels, increase hepatic uptake of LDL-cholesterol and aid
its catabolism to bile acids. Also saponins may lower TG by inhibiting
pancreatic lipase activity (Santosh et al., 2009).
Furthermore, the decline in VLDL cholesterol levels in treated groups could be
directly correlated to a decline in TG levels of these groups, as it is well
established that VLDL particles are the main transporters of TG in plasma
(Santosh et al., 2009). Thus, a simultaneous decline
in both TG and VLDL-cholesterol in treated groups indicates the possible effect
of saponins (Mohana et al., 2010).
The concentrations of total protein, creatinine and activity
of the transaminases ASAT and ALAT, reflect the degree of renal and hepatic
damage generated upon exposure to risk factors of cardiovascular disease
(Wasan et al., 2001) and can lead to various
complications. In this study, there was no significant difference (p
<0.05) in the markers of hepatic toxicity (ASAT and ALAT activities) as
compared to the positive control after the sub acute experiment. There was a
significant decrease (p=0.05) in the markers of renal toxicity (total protein
and creatinine levels) as compared to the positive control. These could be
attributed to polyphenols in the extracts of F. ovata that may act in
the regeneration of reduced glutathione as a proton donor to counteract the
action of free radicals.
The low concentration of nitric oxide in the positive control
as compared to the test groups at the level of the plasma could be due to
increased concentration of reactive oxygen species which lead to endothelia
dysfunction especially by inhibiting the synthesis and action of nitric oxide.
This correlates with the work done by Hadi et al.
(2007). The concentration of Nitric oxide was high in the extract FOHT
than in the extract FOHF.
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