Antidiabetic and Hypolipidemic Effects of
Methanol Leaf Extract of Newbouldia laevis in
Alloxan Induced Diabetic Rats
Bosha JA1*, Sule S1 and Asuzu IU2
1Department of Vet. Physiology and Pharmacology, Federal University of Agriculture Makurdi, Nigeria
2Department of Vet. Physiology and Pharmacology, University of Nigeria, Nigeria
Submission: June 06, 2019; Published: July 09, 2019
*Corresponding author:Bosha Joel Aondohulugh, Senior Lecturer, Department of Vet. Physiology and Pharmacology, Federal University of Agriculture Makurdi, PMB2373 Makurdi, Benue State, Nigeria
How to cite this article: Bosha JA, Sule S, Asuzu IU. Antidiabetic and Hypolipidemic Effects of Methanol Leaf Extract of Newbouldia laevis in Alloxan
Induced Diabetic Rats. Adv Res Gastroentero Hepatol. 2019; 13(3): 555863. DOI:10.19080/ARGH.2019.13.555863.
The antidiabetic, hypolipidemic, liver and kidney function effects of the methanol leaf extract of Newbouldia laevis (NLE) was carried out in wistar albino rats. Diabetes was induced by single intraperitoneal administration of 150 mg/kg alloxan monohydrate in overnight fasted albino rats. Newbouldia laevis extract (NLE) caused a significant (P < 0.05) time-and dose-dependent reduction in FBS especially at the dose of 250 mg/kg which caused 60.2% reduction of FBS at 24th h compared to the negative control. All doses of NLE used in the study caused significant (P < 0.05) doses-dependent decrease in all serum lipids except high density lipid level of treated rats compared to the negative control. It significantly (p < 0.05) reduced the cardiovascular risk index as represented by coronary risk and atherogenic indices, just like glibenclamide. The extract caused significant (p < 0.05) dose-dependent decrease in Alanine Aminotransferase (ALT) in the liver. Kidney function test showed significant (P < 0.05) dose-dependent decrease in serum urea and creatinine levels. The extract (NLE) has demonstrated good antidiabetic and hypolipidemic activities comparable to glibenclamide a standard antidiabetic drug and its folkloric use as an antidiabetic herb is justified and can be a good candidate as a hypolipidemic drug.
Diabetes mellitus is an abnormal metabolic condition in which there is excess glucose in the blood due to disturbance in homeostasis of carbohydrate, protein and lipid metabolism regulated by the hormone insulin Dewanjee & Rakesh et al. [1,2]. This primary defect in glucose metabolism results in wide spread multi-organ complications that encompass virtually every system of the body Wadker et al. . This is so because most of the body cells utilize glucose for their energy need
Diabetes mellitus is a disease condition of both humans and other animals Frode & Medeiros . The disease incidence is on the increase and has now become an epidemic that kills more than HIV/AIDS Jerald et al. . The currently estimated worldwide prevalence is 8.3% and is projected to be 9.9% in the next 20 years
Staykova et al. . According to WHO  about 377 million people
had diabetes worldwide in 2013 and about 3.4 million died from consequences of high blood sugar in 2004. In Africa about 10.4 million people were reported to have DM in 2008 and this figure is expected to rise to 18.7 million by 2025 Hamman .
In other animals, DM is more common in dogs and cats Davidson , Rand & Marshall ; Khan . The disease has also been reported in horses Durham et al. , cattle, pigs and sheep Gould & Clark [13,14], and also in guinea pigs Lang & Mungar , Frode & Medeiros . The trend of DM in other animals is also on the increase just as in humans especially in the companion animals (dogs and cats). The number of dogs diagnosed with diabetes mellitus has increased in the last 30 years Fleeman & Rand . The disease is majorly classified into two types: type 1
and type 2 diabetes according to world health organization WHO
. Although, other forms of the disease do exist. For example,
gestational diabetes, malnutrition related diabetes etc. ADA .
The ultimate goal of all diabetes treatment strategies is to
lower blood glucose concentrations to levels that approximate
those representing normal range and its maintenance there of
Wadker et al. . This has shown to lessen the risk of development
and progression of the disease process and its complications.
Emphasis is usually on cardiovascular risk reduction particularly
hypertension control and correction of dyslipidemia Defronzo &
Abdul-Ghani . Since time immemorial patients with type 2
diabetes have been treated orally with a variety of plant extracts in
folk medicine Ivorra et al. ; Andrede-cetto & Heinrich . One
of such plants is Newbouldia laevis Bosha et al. . The present
hypoglycaemic agents used in the treatment of DM have shown
reduced efficacy due to drug resistance and have many serious side
effects. Also, available literature did not show enough scientific
validation for Newbouldia laevis’ traditional use. This study was
therefore designed to evaluate the antidiabetic, hypolipidemic,
liver and kidney functions as well as cardiovascular risk effects of
N. laevis leaf extract in diabetic rats.
Leaves of Newbouldia laevis were collected in Makurdi, Benue
State North Central Nigeria and identified by a Botanist, with the
Voucher specimen UAM/FHM/205 deposited at the Hebarium of
the University of Agriculture, Makurdi. It was extracted by cold
maceration in 80% methanol for 72 h and was concentrated in
vacuo using rotary evaporator (Rotavapor-R-215) and stored as
Newbouldia laevis extract (NLE). Diabetes was induced in albino
rats by single intraperitoneal injection of 150 mg/kg alloxan
monohydrate (Acrose, New Jersey USA) after overnight fast
Szudelski . The effect of NLE on alloxan-induced diabetes was
carried out using diabetic rats divided into 5 groups of 8 rats each.
Any rat with fasting blood sugar ≥ 7.0 mMol/l was considered
diabetic using Accu-check Advantage II® (Roche Diagnostics, New
Jersey USA) Bosha et al. .
Rats in group 1 and 2 were given 10 ml/kg distilled water
(negative control) and 2 mg/kg glibenclamide (M.P. biomedicals
inc, France) (positive control), respectively. Rats in group 3-5 were
given 62.5, 125 and 250 mg/kg of NLE respectively for 21 days,
all by gastric gavage. The fasting blood sugar (FBS) was measured
at 0, 1, 3, 6, 24 h post drug or extract administration. Blood was
collected via the heart under light chloroform anesthesia on day
21 for serum biochemistry assessment. The data was presented
as mean± standard error of mean (SEM) and one-way Analysis of
Variance (ANOVA) was used to analyze the result. Significance was
accepted at p < s 0.05. The result is presented in tables.
The effect of graded-doses of NLE on the FBS of alloxaninduced
hyperglycaemic rats after 24 hours is presented in
Table 1. The result indicated that there was an increase in the
mean FBS of rats in the negative control group from 25.3 ± 4.12
mMol/l to 28.3 ± 2.45 mMol/l from the 0 to 24 hours respectively
representing 11.9 % increase. The various doses of the extract and
the reference drug (glibenclamide) produced significant (p < 0.05
– 0.01) dose and time-dependent decreases in FBS levels of treated
rats when compared to the negative control especially at 6 and 24
hours. The extract doses of 62.5, 125.0 and 250.0 mg/kg produced
a decrease in FBS of the rats by 24%, 25% and 33.6% at 6 hour
and 27.8% 55.3% and 60.2% at 24 hour respectively as against
40% and 51.5% reduction of the FBS in rats by the reference drug
at the same time frame of 6 and 24 hours respectively. The highest
FBS reductions by all doses of the extract and the reference drug
(glibenclamide) were obtained at 24 hours. Also, at 24 hours,
there was no significant difference (p > 0.05) between the extract
(125.0 and 250.0 mg/kg) and the reference drug glibenclamide
*P < 0.05, ** P < 0.01, when compared to negative control
Represent increase in blood sugar level
The mean serum level of total cholesterol, triglycerides, high
density lipoproteins (HDL) low density lipoproteins (LDL) and
very low-density lipoproteins (VLDL) of the controls and NLEtreated
diabetic rats as well as the atherogenic index (AI) and
coronary risk index (CRI) are shown in Table 2. Glibenclamide (2
mg/kg) and NLE (125 and 250 mg/kg) induced various levels of
significant (p < 0.05-0.001) reduction in the serum levels of total
cholesterol, triglycerides, LDL, VLDL, AI and CRI of the diabetic
rats when compared with the negative control. The activity of
NLE at the highest dose (250 mg/kg) was comparable to that of
glibenclamide in all the parameters tested. NLE at the lowest dose
(62.5 mg/kg) produced some reductions of the lipid profile and
cardiovascular risk index, which were not statistically significant
(p > 0.05). NLE at 62.5, 125.0 and 250.0 mg/kg produced a dosedependent
significant (p < 0.05) increase of HDL in the diabetic
rats when compared to the negative control.
*P<0.05, **P<0.001 when compared to negative control group.
HDL: High Density Lipoproteins; LDL: Low Density Lipoproteins; VLDL: Very Low-Density Lipoproteins; AI: Atherogenic Index; CRI: Coronary Risk
The results of the effect of NLE on liver marker enzymes
of alloxan-induced diabetic rats are presented in Table 3. The
result indicated that there was significant (p < 0.05) decrease
in mean ALT in the glibenclamide and the NLE treated groups
when compared to the negative control except in the 62.5 mg/kg
dose. The extract at all doses used did not cause any significant
(p > 0.05) decrease in the other liver enzymes except for ALP at
the 250 mg/kg dose. The total protein and bilirubin levels were
not significantly (p > 0.05) changed in all treated groups when
compared to the negative control group.
*p < 0-05 when compared to negative control group.
The result of the effect of NLE on kidney function test in alloxaninduced
diabetic rats is presented in Table 4. The result showed
significant (p < 0.05) reduction in creatinine by the various doses
(62.5, 125.0 and 250.0 mg/kg) of NLE and glibenclamide (2 mg/
kg). Creatinine was reduced from 0.40±0.16 mg/dl to 0.15±0.11
mg/dl in rats treated with the highest dose of NLE (250 mg/kg)
representing 62.5% decrease. Serum urea reduced from 36.6±2.1
mg/dl in the negative control group to 25.3±2.1 mg/dl. The serum
urea concentration of rats treated with 125, and 250 mg/kg were
significantly (p < 0.01) different from the groups treated with
glibenclamide (2 mg/kg) and NLE at 62.5 mg/kg.
*p < 0.05, **p < 0.01 when compared to the negative control
The ability of NLE to reduce the fasting blood sugar (FBS) of
rats was tested as a means of evaluating its antidiabetic activity
through a single intraperitoneal administration of 150 mg/kg
of alloxan monohydrate. Fasting blood sugar (FBS) is a test of
carbohydrate metabolism which measures blood glucose after
a fast, which is usually 12-18 h Szudelski . During this time,
the body stimulates the release of the hormone glucagon which
in turn releases glucose in to the blood stream through a catabolic
process. Under normal circumstances, the body produces and
processes insulin to counteract the rise in glucose levels, but
in diabetes mellitus this process is impaired, and tested blood
glucose levels remain usually high Kaufman et al. .
Experimental diabetes is usually induced using alloxan
monohydrate or Streptozotocin Szudelski ; Frode & Medeiros
. Alloxan monohydrate (2, 4, 5, 6, - Tetraoxyprimidine, 2, 4,
5, 6, - pyrimidinetetrone) induces diabetes by the destruction
of the β-cells of the islets of Langerhans of the pancreas which
leads to decrease in insulin levels in the body and subsequent
hyperglycaemia. Alloxan mediates its cytotoxic activity through
reactive oxygen species (ROS) especially hydrogen peroxide with
simultaneous massive increase in cytosolic Ca2+ concentration
which causes rapid destruction of β-cells Szudelski ; Frode &
Medeiros . The pancreas is especially susceptible to the action
of alloxan induced free radical-damage; subsequently, there is a
decrease in endogenous insulin and this affects the utilization
of glucose by the body tissues. It also leads to elevated blood
glucose level, decreased protein content and increased levels of
serum cholesterol, triglycerides and other bad lipids Yamamoto &
Dhanabal et al. [26,27]. In this present study, diabetes was induced
chemically in the rats through a single intraperitoneal injection
of alloxan monohydrate at a dose of 150 mg/kg body weight as
described by Szudelski ; Frode & Medeiros .
The rats were considered diabetic whenever their fasting
blood sugar (FBS) was 7.0 mMol/l and more WHO, ; Turner et
al. . In the present study, methanol leaf extract of Newbouldia
laevis (NLE) at doses of 62.5, 125.0 and 250.0 mg/kg body weight
caused significant (p < 0.05 – 0.01) dose and time-dependent
decreases in the FBS levels of the alloxan-induced diabetic
rats. The time of maximum effect was at the 24th h in the dose
response study. The dose and time-dependent reductions in the
FBS levels also manifested in the subacute study of 21 days oral
administration of NLE Bosha et al. . The NLE at the highest
dose (250.0 mg/kg) caused 60.2% decreases in FBS at 24 h, when
compared to the negative control rats as against the reference drug
glibenclamide (2 mg/kg) which caused 51.5% decrease under the
same condition (Table 1). The dose and time-dependent decrease
of FBS in diabetic rats by Newbouldia laevis has been reported by
other workers also Tanko et al. ; Owolabi et al. ; Kolawole
et al. ; Bosha et al. ; Bosha et al. ; Bosha et al. 
Diabetes mellitus is also associated with increase in serum
lipid which usually leads to coronary heart disease complications.
The lipids that are normally elevated in diabetes mellitus include
total cholesterol, triglycerides, low density lipids, (LDL), very
low-density lipids (VLDL) but a decrease in high density lipids
(HDL) ADA [18,34]. The increase in the concentration of body
lipids especially the visceral lipids results in the liberation of some
lysosomes and other pro-inflammatory substances like some
free fatty acids and cytokinins that trigger inflammation and cell
degeneration, which are capable of causing other complications
Tajudin & Nasiruddin ; Umesh et al. . In the present study,
NLE significantly (p 0.05) reduced the elevated serum levels of
total cholesterol, triglycerides, LDL and VLDL of the treated rats
dose-dependently when compared to the negative control group
NLE also reduced the cardiovascular risk index dosedependently
as shown by the reduction of the Coronary Risk Index
(CRI) from 3.55 in the control group to 1.81 and Atherogenic Index
(AI) from 2.56 to 0.81, just like glibenclamide. These reductions are
likely beneficial in preventing the development of the disease and
its complications Cho et al. . These findings also point to the
fact that NLE has some cardiovascular protective property and can
positively intervene in cardiovascular complications associated
with the natural history of diabetes. Another good finding about
NLE is that its dose-dependently increased the concentration of
HDL which is also needed to ameliorate the cardiac risk associated
with diabetes mellitus
The liver is the major organ of metabolism and
biotransformation as well as gluconeogenesis and glycogenolysis.
Glucose homeostasis is physiologically maintained by the balance
between glucose production by the liver and glucose utilization
by the peripheral tissues Duncan & Bond ; Navarro et al. .
The effect of substances on the liver depends on the duration of
exposure and the chemical nature of the substance.
Alloxan monohydrate is toxic to the liver apart from the
pancreas such that the induction of diabetes with alloxan also
causes damage to the liver and affects its function and integrity
El-Demerdash et al. . This damage is manifested by leakages
of liver enzymes into the blood and this leads to increased enzyme
levels Navarro et al. . NLE caused dose-dependent decrease in
elevated serum level of these enzymes (AST, ALT and ALP) but only
ALT was significant (p < 0.05) when compared to the untreated
control (Table 3). Increase beyond the normal level of some or all
of these enzymes (AST, ALT and ALP) in the serum are indicative of
toxicity of the liver by drugs or other hepatic toxins Ramaiah .
Among all the enzymes, ALT is the most specific to the liver
and a much better parameter to detect liver injury. Aspartate
aminotransferase (AST) apart from being observed in liver injury
is also associated with the diseases of other organs like the heart
and skeletal muscles Ozer et al. . Alkaline phosphatase (ALP)
is mostly present in the cells linning the billiary duct system of
the liver and is used to diagnose obstruction to the billiary system
such that its elevation in the blood is associated with cholestatic
diseases such as gallstone or tumour blocking the bile duct Burtis & Ashwood ; Kolawole et al. . In this present study, there
was no significant change in the values of AST, ALT and ALP
in the duration of the study. Kolawole et al.  also reported
nonsignificant changes in these liver enzymes in rats. This also
suggests a hepatoprotective effect of NLE in diabetes which may be
due to cell membrane stabilization and repair of damaged tissues
as mentioned by Argawal et al. . Bosha et al.  reported the
erythrocytes and membrane protective effects of NLE in diabetic
The protein level of the NLE-treated rats was slightly lower
than the untreated diabetic group though the difference was not
statistically significant. This does not agree with the findings of
Duncan & Bond  and Ezeja et al. . They reported that
the protein levels of the treated rats were slightly reduced after
3 weeks of diabetic induction but higher than the control. In this
study, the protein levels of treated rats were slightly reduced but
lower than the untreated control. Among the NLE-treated groups
there was a dose-dependent difference in the protein level. The
glibenclamide-treated group also showed a similar decrease in
protein level. The serum bilirubin of the control and the treated
groups of rats did not show any significant difference. This lack
of difference in the serum bilirubin level may indicate that there
was no hepatic injury. Bilirubin is a product of haemoglobin
breakdown and is associated with hepatic diseases like jaundice
and ineffective erythropoiesis. Increase in the level of bilirubin
indicates the depth of jaundice in the individual Thapa & Walia
Kidneys are major organs of excretion and play very important
roles in glucose metabolism. Their role in gluconeogenesis and
glucose excretion helps in the development, maintenance and
resolution of hyperglycaemia Marseric . It takes up glucose
from circulation and reabsorbs glucose from glomerular filtrate.
The kidney responds to noxious substances or injuries in various
ways ranging from decreased waste elimination to cell death.
The major biochemical parameters that are measured to access
the integrity and normal function of the kidney include increased
blood urea nitrogen (BUN) or increased plasma creatinine levels
Gerich ; Braide & Anika .
In this study, untreated diabetic rats showed higher levels of
serum urea and creatinine when compared to the treated groups.
Kolawole et al.  also reported a similar finding in rats. NLE
showed a dose-dependent decrease in serum urea nitrogen (SUN).
At the highest dose (250 mg/kg), it performed significantly (p
0.05) better than the reference drug glibenclamide. This may be
possible due to improved waste product clearance and adequate
regulation of blood pH which are affected in diabetes mellitus
due to disturbance of tubular integrity Frode & Medeiros .
This significant reduction in both serum urea and ceratinine
suggest that NLE may improve nephropathy and its associated
complications in diabetes (Table 4). Serum urea and creatinine are
important markers of kidney dysfunction Mukinda & Eagles .
In conclusion, Newbouldia laevis leaf extract (NLE) has
demostrated significant antidiabetic activity which is comparable
to glibenclamide a standard sulfanylurea, in this study. It also
demonstrated dyslipidemic effects by lowering the bad lipids and
increasing the good lipids thereby reducing the cardiovascular risk
index as much as glibenclamide. It also protects the liver and the
kidney by lowering the index enzymes. This establishes the basis
for its pharmacological use as an antidiabetic plant in Nigerian
folk medicine and can be a good candidate for hypolipidemic drug.
Dr Bosha acknowledged the support of University of
Agriculture, Makurdi for the study leave to carry out the work.
He also acknowledges TET Fund through the same University for
partly sponsoring the work.
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