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Key words: antihyperglycemic, antioxidant, diabetes,
glibenclamide, Lagenaria siceraria,
streptozotocin
SUMMARY
The present study was carried out to evaluate the
antihyperglycemic activity of methanol extract of
Lagenaria siceraria aerial parts (MELS) for its
purported use in diabetes. Hyperglycemia was induced
by streptozotocin (50 mg/kg, i.p.) in rats. Treatment
was done by MELS at doses of 200 and 400 mg/kg, p.o.
for 14 days. Glibenclamide (500 µg/kg) was used as a
reference drug. Antihyperglycemic potential was
assessed by fasting blood glucose (FBG) measurement
(on days 0, 4, 8 and 15), biochemical tests (SGPT,
SGOT, ALP, total cholesterol, triglycerides),
antioxidant assay (lipid peroxide, catalase and
glutathione) and histologic study of the liver, kidney
and pancreas tissue. Significant reduction (P<0.001)
in FBG levels was observed with treatment duration.
Antioxidant and biochemical parameters were
significantly improved by MELS and glibenclamide
treatment. Histologic observations showed good
correlations with the results obtained. The study
explored the potent antihyperglycemic activity of
MELS, which is probably attributable to its rich
flavonoid content.
INTRODUCTION
Diabetes mellitus is a chronic metabolic disorder
characterized by the classical symptom of
hyperglycemia, which in turn leads to various acute
and chronic complications if left untreated and may
cause massive damage to the renal, cardiovascular,
retinal and neurologic systems. It occurs as a result of
a relative or an absolute lack of insulin, or its action on
the target tissue, or both (1,2). Despite the great strides
made in understanding and management of diabetes,
the incidence of diabetes mellitus is on rise all over the
world, especially in Asia and Africa, and is likely to
rise to up to 300 million or more by the year 2025
(3,4). Many synthetic hypoglycemic agents are
currently available but they are either too expensive or
produce undesirable side effects on chronic use (5).
Traditionally, many indigenous plants have been used
successfully for the management of the disease
throughout the world; some of them have been
49
Diabetologia Croatica 40-2, 2011
1Department of Pharmaceutical Technology,
Jadavpur University, Kolkata-700 032, India
2Guru Nanak Institute of Pharmaceutical Science and
Technology, 157/F, Nilgunj Road, Panihati,
Kolkata-700114, India
Original Research Article
Received: February 21, 2011
Accepted: May 9, 2011
ANTIHYPERGLYCEMIC ACTIVITY OF LAGENARIA SICERARIA
AERIAL PARTS ON STREPTOZOTOCIN INDUCED
DIABETES IN RATS
Prerona Saha1,2, Upal K. Mazumder1, Pallab K. Haldar1, Sriparna Kundu Sen1, Sagar Naskar1
Corresponding author: Upal K. Mazumder, Department of Pharmaceutical
Technology, Jadavpur University, Kolkata-700 032, India
E-mail: prerona_saha@rediffmail.com
evaluated experimentally and their active ingredients
have been isolated (6,7). However, a number of such
potential plants have remained unexplored.
Lagenaria siceraria (Mol.) Standley, commonly
known as bottle-gourd (in English), belongs to the
Cucurbitaceae family. The plant is widely available
throughout India. It is a climbing or trailing herb, with
bottle- or dumb-bell shaped fruits. Both its aerial parts
and fruits are commonly consumed as a vegetable.
Traditionally, it is used as medicine in India, China,
European countries, Brazil, Hawaiian island, etc. for
its cardiotonic, general tonic and diuretic properties
(8). Further, the antihepatotoxic, analgesic and anti-
inflammatory, hypolipidemic, antihyperglycemic,
immunomodulatory and antioxidant activities of its
fruit extract have been evaluated (9-14). Lagenaria
(L.) siceraria fruits are a good source of vitamin B
complex, ascorbic acid, fibers, proteins, cucurbitacins,
saponins, fucosterols and compesterols, polyphenolics
and flavone-C-glycoside (9,10,15-17). Methanol
extract of its leaves showed the presence of sterols,
polyphenolics, flavonoids, saponin, protein and
carbohydrates (18). A novel protein, lagenin, has also
been isolated from its seeds and it possesses antitumor,
immunoprotective and antiproliferative properties
(19). Although extensive studies have been carried out
on its fruits and seeds, the pharmacology of the aerial
parts of L. siceraria has not been studied yet. In many
countries, this plant has been used traditionally as a
single treatment for diabetes mellitus (20). The present
investigation was therefore carried out to evaluate the
antihyperglycemic potential of the methanol extract of
L. siceraria aerial part (MELS) on streptozotocin
(STZ) induced diabetes in rats.
MATERIALS AND METHODS
Plant material
The aerial parts of L. siceraria were collected in
November 2008, from Madanpur, West Bengal, India,
and identified by the Botanical Survey of India,
Howrah, India. A voucher specimen (P/LS/1/08) was
retained in our laboratory for further reference.
Preparation of plant extract
The aerial parts were dried under shade and
powdered in a mechanical grinder. The powdered
material was extracted with methanol using a Soxhlet
apparatus. This extract was filtered and concentrated
in vacuo in a Buchi evaporator, R-114 and kept in a
vacuum desiccator until use. The yield was 18.13%
w/w with respect to dried powder. Aqueous suspension
of MELS was prepared using 2% (v/v) Tween-80 and
used for oral administration.
Animals
Healthy Wistar albino rats (160±20 g) were used in
the present study. They were maintained at standard
laboratory conditions and fed commercial pellet diet
(Hindustan Lever, Kolkata, India) and water ad
libitum. The animals were acclimatized to laboratory
conditions for one week before commencement of
experiment. The experiments were performed based
on animal ethics guidelines of the University Animals
Ethics Committee.
Preliminary phytochemical screening
Preliminary phytochemical screening was carried out
following the standard procedures (21).
Acute toxicity study
Healthy Wistar albino rats (160±20 g) of either sex,
starved overnight, were divided into five groups (n=4).
Group I-IV animals were orally fed MELS in
increasing dose levels of 0.5, 1.0, 1.5 and 2.0 g/kg
b.w., while group V (untreated) served as control. The
animals were observed continuously for the first 2 h
for any gross change in behavioral, neurologic and
autonomic profiles or any other symptoms of toxicity
and mortality if any, and intermittently for the next 6 h
and then again at 24 h , 48 h and 72 h for any lethality
or death. One-tenth and one-fifth of the maximum safe
dose of the extract tested for acute toxicity were
selected for the experiment (22).
50
P. Saha, U. K. Mazumder, P. K. Haldar, S. Kundu Sen, S. Naskar / ANTIHYPERGLYCEMIC ACTIVITY OF LAGENARIA SICERARIA
AERIAL PARTS ON STREPTOZOTOCIN INDUCED DIABETES IN RATS
Study in normoglycemic animals
Healthy rats were divided into two groups (n=6).
After overnight fasting with free access to water,
fasting blood glucose (FBG) level of each animal was
determined at the beginning of the experiment (at 0 h).
Animals in control group (group I) received only the
vehicle and the test group animals (group II) were
treated with a high dose of MELS (400 mg/kg b.w.)
orally. Blood sugar levels were determined again at
½ h, 1 h, 2 h and 3 h after oral administration of test
samples to assess the effect of test samples on
normoglycemic rats.
Induction of diabetes
A freshly prepared solution of STZ (50 mg/kg) in ice-
cold citrate buffer (0.1 M, pH 4.5) was injected
intraperitoneally to the overnight fasted rats (23). After
72 h of STZ administration, the blood glucose levels
were measured and the rats showing blood glucose
level >200 mg/dL were considered to be diabetic and
were used in the study.
Study in STZ induced diabetic rats
Healthy Wistar albino rats were divided into five
groups (n=6). Treatment was done for 14 days. Group
I: normal rats received only vehicle; groups II, III, IV
and V: STZ induced diabetic rats. Group II received
only vehicle and served as STZ control group. Groups
III and IV were orally administered with MELS, 200
and 400 mg/kg b.w., respectively, while group V was
treated with the reference drug, glibenclamide (0.5
mg/kg, p.o.).
Testing of fasting blood glucose and body weight
FBG level of each animal was monitored on days 0,
4, 8 and 15. Drop of blood was collected from the tip
of the tail vein of each rat and FBG level was
measured using One Touch Glucometer, Horizon
(Lifescan, Johnson and Johnson Company). Initial and
final body weights were also recorded.
Estimation of biochemical parameters
On day 15, blood samples were collected from the
retro-orbital plexus of the rats and serum was
separated for biochemical estimation of serum
glutamic pyruvate transaminase (SGPT), serum
glutamic oxaloacetate transaminase (SGOT) (24),
alkaline phosphatase (ALP) (25), total cholesterol and
triglycerides (26). All analyses were performed by
using commercially available kit from Span
Diagnostics Ltd.
Evaluation of antioxidant properties
After blood collection, all animals were sacrificed by
euthanasia. Liver, kidney and pancreas were collected
for the estimation of tissue lipid peroxide (LPO) (27),
reduced glutathione (GSH) (28) and catalase (CAT)
(29) levels for the antioxidant study.
Histologic studies
After sacrificing the rats, parts of the pancreas, liver
and kidney tissues were collected for histologic
studies. The tissues were washed in normal saline and
fixed immediately in 10% formalin for a period of at
least 24 h, dehydrated with alcohol, and embedded in
paraffin, cut into 4- to 5-µm thick sections and stained
with hematoxylin-eosin dye for photomicroscopic
observation.
Determination of total phenolic compounds in
the extract
The amount of total phenolic compounds in MELS
was determined using Folin-Ciocalteu’s reagent and
sodium carbonate solution, and absorbance was
measured at 760 nm (30). A calibration curve of
standard pyrocatechol was prepared and the results
were expressed as mg of pyrocatechol equivalents/g of
dry extract.
51
Diabetologia Croatica 40-2, 2011
P. Saha, U. K. Mazumder, P. K. Haldar, S. Kundu Sen, S. Naskar / ANTIHYPERGLYCEMIC ACTIVITY OF LAGENARIA SICERARIA
AERIAL PARTS ON STREPTOZOTOCIN INDUCED DIABETES IN RATS
Determination of total flavonoid content in the
extract
Total flavonoid content of MELS was determined
spectrophotometrically (31). Briefly, 0.5 mL of 2%
aluminum chloride in ethanol was mixed with the
same volume of extract (1.0 mg/mL). Absorption
readings at 415 nm were taken after 1 h against a blank
(ethanol). Total flavonoid content was determined
using a standard curve with quercetin (0-50 mg/L).
The mean of three readings was used and expressed as
mg of quercetin equivalents/g of dry extract.
Statistical analysis
Values were expressed as mean ± SEM. Data were
statistically evaluated by one-way analysis of variance
(ANOVA) followed by post hoc Dunnett’s test using
SPSS software. Pvalues less than 0.01 were
considered statistically significant.
RESULTS
Preliminary phytochemical screening of MELS
revealed the presence of polyphenolics, flavonoids,
glycosides, triterpinoids, saponin and carbohydrates.
In the acute toxicity study, MELS did not show any
mortality or toxic effect up to the dose of 2 g/kg b.w.;
accordingly, 200 and 400 mg/kg b.w. were taken as the
low and high dose of MELS for the in vivo experiment.
Blood glucose level of normoglycemic study (NG)
showed no significant effect of MELS on
normoglycemia (results not shown).
The increased FBG level in STZ induced diabetic
rats was significantly reduced (P<0.001) by MELS
treatment and it was found to be lowered up to 65.74%
and 68.57% at the dose of 200 and 400 mg/kg b.w.,
respectively. FBG and change in body weight in the
STZ induced diabetic rats in 14-day experiment are
52
P. Saha, U. K. Mazumder, P. K. Haldar, S. Kundu Sen, S. Naskar / ANTIHYPERGLYCEMIC ACTIVITY OF LAGENARIA SICERARIA
AERIAL PARTS ON STREPTOZOTOCIN INDUCED DIABETES IN RATS
Mean serum FBG ± SEM (mg/dL)
Group Day 0 Day 4 Day 8 Day 15 % Change
Normal control 82.50±1.09 81.33±2.09 83.17±1.38 15±0.57 0.81
Diabetic control 260.33±9.42a,# 315.33±7.25a,# 304.33±3.36a,# 296.67±2.46a,# 13.96
MELS (200 mg/kg) 250.50±5.30 200.33±14.84b,* 110.00±6.06b,* 85.83±3.73b,* -65.74
MELS (400 mg/kg) 257.17±9.36 128.83±10.83b,* 84.33±4.15b,* 80.83±1.74b,* -68.57
Glibenclamide (0.5 mg/kg) 260.50±7.42 229.33±4.43b,* 169.33±2.91b,* 93.00±2.16b,* -64.30
Values are mean ± SEM; (n=6): adiabetic control group vs. normal control group,
#P<0.001; btreated groups vs. diabetic control group, *P<0.001; the level of significance was assessed by one-way ANOVA followed by post hoc Dunnett's test.
Table 1. Effect of methanol extract of Lagenaria siceraria (MELS) on fasting blood glucose (FBG) level in control
and streptozotocin (STZ) diabetic rats
Body weight (g)
Group Initial Final Change
Normal control 155.00±3.87 156.00±3.54 1.00±0.93
Diabetic control 157.50±3.82 123.33±3.33 -34.17±1.54a,#
MELS (200 mg/kg) 161.67±6.15 136.50±6.73 -25.17±1.20b,*
MELS (400 mg/kg) 154.17±5.39 135.17±5.91 -19.00±1.39b,*
Glibenclamide (0.5 mg/kg) 173.83±2.29 155.83±2.51 -18.00±1.65b,*
Values are mean ± SEM; (n=6): adiabetic control group vs. normal control group,
#P<0.001; btreated groups vs. diabetic control group, *P<0.001; the level of significance was assessed by one-way ANOVA followed by post hoc Dunnett's test.
Table 2. Effect of methanol extract of Lagenaria siceraria (MELS) on body weight in control and streptozotocin
(STZ) diabetic rats
summarized in Table 1 and Table 2, respectively,
indicating MELS as being equipotent to the reference
drug, glibenclamide.
After 14-day experiment, the activities of serum
enzymes such as SGOT, SGPT and ALP were
significantly elevated in diabetic control groups (Fig.
1a), which was found to return to normal level upon
supplementation with MELS (200 and 400 mg/kg) and
glibenclamide (0.5 mg/kg). Figure 1b reveals
significant reduction in total cholesterol and
triglyceride levels in the MELS treated groups as
compared to diabetic control group.
As shown in Table 3, lipid peroxide level in the liver,
pancreas and kidney tissues increased significantly in
STZ induced diabetic rats as compared to normal
group, and showed significant reduction (P<0.001)
53
Diabetologia Croatica 40-2, 2011
P. Saha, U. K. Mazumder, P. K. Haldar, S. Kundu Sen, S. Naskar / ANTIHYPERGLYCEMIC ACTIVITY OF LAGENARIA SICERARIA
AERIAL PARTS ON STREPTOZOTOCIN INDUCED DIABETES IN RATS
LPO level (nM/mg wet tissue) GSH level (μμg/mg wet tissue)
CAT level (μμM of H2O2
decomposed/min/mg wet tissue)
Group
Normal control 126.86 ±
2.68
220.29 ±
0.59
209.43 ±
0.32
20.88 ±
0.22
69.12 ±
0.70
22.14 ±
0.13
0.54 ±
0.04
3.90±
0.29
1.78 ±
0.21
Diabetic control 302.08 ±
5.07 a,##
395.40 ±
1.06 a,##
330.24 ±
0.73 a,##
8.84 ±
0.20 a,##
24.93 ±
0.33 a,##
11.28 ±
0.20 a,##
0.25 ±
0.02 a,#
1.25±
0.09a,#
0.41 ±
0.06 a,##
MELS (200 mg/kg) 200.94 ±
3.03 b,**
291.65 ±
2.09 b,**
235.78 ±
2.05 b,**
16.03 ±
0.62 b,**
52.39 ±
1.93 b,**
20.48 ±
1.22 b,**
0.39 ±
0.02 b,*
2.13±
0.04b,*
1.40 ±
0.03 b,*
MELS (400 mg/kg) 147.92 ±
2.44 b,**
232.08 ±
1.54 b,**
206.47 ±
1.36 b,**
20.04 ±
1.83 b,**
59.56 ±
0.53 b,**
22.51 ±
1.00 b,**
0.51 ±
0.04 b,*
3.12±
0.04 b,*
1.80 ±
0.06 b,**
Glibenclamide (0.5 mg/kg) 144.32 ±
2.69 b,**
234.88 ±
0.62 b,**
212.29 ±
0.46 b,**
18.53 ±
0.16 b,**
66.31 ±
0.54 b,**
20.51 ±
0.33 b,**
0.53 ±
0.04 b,*
3.06±
0.31 b,*
1.43 ±
0.17 b,*
Values are mean ± SEM; (n=6): adiabetic control group vs. normal control group,
#P<0.01, ##P<0.001, btreated group vs. diabetic control group, *P<0.01, **P<0.001; the level of significance was assessed by one-way ANOVA followed by post hoc Dunnett's test
Table 3. Effect of methanol extract of Lagenaria siceraria (MELS) on tissue lipid peroxide (LPO), reduced
glutathione (GSH) and catalase (CAT) levels in control and streptozotocin (STZ) diabetic rats
Figure 1a. Effect of methanol extract of Lagenaria
siceraria (MELS) on some biochemical parameters
(serum biomarker enzyme levels) in control and
streptozotocin (STZ) diabetic rats. Values are mean ±
SEM; n=6 per group. Treatment was done for 14 days.
aDiabetic control group vs. normal control group,
#P<0.001; btreated groups vs. diabetic control group,
*P<0.001; the level of significance assessed by one-
way ANOVA followed by post hoc Dunnett’s test.
0
50
100
150
200
250
300
SGPT SGOT ALP
IU/dl
Normal Control (2 % Tween 80) Diabeti c Control MELS (200 mg/kg) MELS (400 mg/kg) Glibenclamide (0.5 mg/kg)
a,#
a,#
a,#
b,*
b,*
b,*
b,*
b,*
b,*
b,*
b,*
b,*
Figure 1b. Effect of methanol extract of Lagenaria
siceraria (MELS) on some biochemical parameters
(total cholesterol and triglyceride levels) in control
and streptozotocin (STZ) diabetic rats. Values are
mean ± SEM; n=6 per group. Treatment was done for
14 days. aDiabetic control group vs. normal control
group, #P<0.001, btreated groups vs. diabetic control
group, *P<0.001; the level of significance was
assessed by one-way ANOVA followed by post hoc
Dunnett’s test.
0
50
100
150
200
250
300
Triglyceride Total cholesterol
mg/dl
Normal Cont rol (2 % Tween 80) Diabetic Control MELS (200 mg/k g) MELS (400 mg/kg) Glibenclamide (0.5 mg/kg)
a,#
b,*
b,*
b,*
a,#
b,*
b,*
b,*
54
P. Saha, U. K. Mazumder, P. K. Haldar, S. Kundu Sen, S. Naskar / ANTIHYPERGLYCEMIC ACTIVITY OF LAGENARIA SICERARIA
AERIAL PARTS ON STREPTOZOTOCIN INDUCED DIABETES IN RATS
Figure 2. Histologic examination of 14-day experimental rat pancreas: pancreatic sections of normal rats (a)
showed dense Langerhans islets with well preserved cytoplasm and nucleus. Pancreatic sections of
streptozotocin (STZ) intoxicated rats (b) showed loss of cell integrity and islet mass, damaged islets, acini
degradation and polymorphonuclear leukocyte infiltration. Pancreatic sections of low dose and high dose MELS
treated rats (c and d) showed gradual improvement in islet mass and cell integrity. Pancreatic sections of
glibenclamide treated animals (e) showed normal tissue architecture with mild damage.
2a. Pancreas of normal control rats 2b. Pancreas of STZ control rats
2c. Pancreas of low dose MELS treated rats 2d. Pancreas of high dose MELS treated rats
2e. Pancreas of glibenclamide treated reats
55
Diabetologia Croatica 40-2, 2011
P. Saha, U. K. Mazumder, P. K. Haldar, S. Kundu Sen, S. Naskar / ANTIHYPERGLYCEMIC ACTIVITY OF LAGENARIA SICERARIA
AERIAL PARTS ON STREPTOZOTOCIN INDUCED DIABETES IN RATS
Figure 3. Histologic examination of 14-day experimental rat liver: liver section of normal rats (a) showed well
arranged cells and clear large central vein; cytoplasm and nucleus were well preserved. Liver section of diabetic
control group (b) showed complete destruction of hepatocytes, degeneration of central vein, fatty degeneration,
loss of cell structure and damage in cell membrane. Liver section of low dose MELS treated rats (c) disclosed
that MELS (200 mg/kg) treatment was not able to recover completely, however, improvement of damage in the
central vein and hepatocyte necrosis was observed to some extent, whereas liver section of the high dose MELS
(400 mg/kg) treated rats (d) showed restoration of cell architecture to near normal. Liver section of glibenclamide
treated rats (e) showed no damage in the hepatocytes and well arranged cells surrounding the central vein.
3a. Liver of normal control rats 3b. Liver of STZ control rats
3c. Liver of low dose MELS treated rats 3d. Liver of high dose MELS treated rats
3e. Liver of glibenclamide treated reats
56
P. Saha, U. K. Mazumder, P. K. Haldar, S. Kundu Sen, S. Naskar / ANTIHYPERGLYCEMIC ACTIVITY OF LAGENARIA SICERARIA
AERIAL PARTS ON STREPTOZOTOCIN INDUCED DIABETES IN RATS
Figure 4. Histologic examination of 14-day experimental rat kidney: kidney section of normal rats (a) showed the
cortex and medulla portion with lot of well packed glomerular and well arranged tubules. Kidney section of
diabetic control group (b) showed damaged cells with hypertrophy and necrosis and derangement of cells with
glomerulosclerosis. Kidney section of low dose and high dose MELS treated rats (c) and (d) showed
improvement as compared to those of diabetic control group, with slight glomerular hypertrophy in the former
group. Kidney section of glibenclamide treated rats (e) showed complete recovery of the damage.
4a. Kidney of normal control rats 4b. Kidney of STZ control rats
4c. Kidney of low dose MELS treated rats 4d. Kidney of high dose MELS treated rats
4e. Kidney of glibenclamide treated reats
upon supplementation with MELS. In the STZ
induced diabetic control animals, the GSH content and
catalase activity were reduced with respect to normal
control animals, and both were improved in the MELS
treated group, almost comparable to the standard drug
treated animals (Table 3).
Histologic examination revealed degeneration and
necrosis of pancreatic islets in the diabetic control
group (Fig. 2). The cytoplasm of peri-acinar
hepatocytes showed either a single large or multiple
small round empty vacuoles that distended the cell
cytoplasm and displaced the nucleus to the periphery
in histologic liver sections stained with hematoxylin
and eosin. Parenchymatous degeneration was
observed in peripheral regions. Dissociation of
hepatocytes and sinusoidal dilatation occurred due to
these changes (Fig. 3). Degenerated cortex and
medulla and necrosis of tubules were observed in
nephrons of diabetic groups. The glomerulus was
emptied and distal tubules were also damaged in
diabetic nephrons (Fig. 4). These histopathologic
changes were restored to the near normal with MELS
treatment.
Total phenolic and flavonoid content of the extract
was found to be 65.7±0.46 mg pyrocatechol/g dry
extract and 25.32 ±0.80 mg quercetin equivalent/g dry
extract.
DISCUSSION
The present study was carried out to evaluate the
antidiabetic activity of MELS on streptozotocin (STZ)
induced diabetes in rats. STZ-induced hyperglycemia
is a useful experimental model for studying
antihyperglycemic activity. Because of its structural
features, STZ gets selective entry into the βcells of the
islets of Langerhans via the low affinity glucose
transporter GLUT2 in its plasma membrane and
causes destruction of βcells, which leads to a
reduction in insulin release, which in turn results in a
rise in blood glucose concentration, i.e. hyperglycemia
(32). Accordingly, significantly high levels (P<0.001)
of FBG were observed in STZ control group rats and
remained high throughout the experimental period.
STZ-induced diabetic rats treated with the extract
showed a significant reduction in blood sugar levels
compared to STZ control group. This decrease in
blood sugar levels may be attributed to stimulation of
the residual pancreatic mechanism or to a probable
increase in the peripheral utilization of glucose (33).
Normoglycemic studies, however, revealed MELS to
have no effect on euglycemia. This implies that the
extract is probably acting through any of the
extrapancreatic mechanisms rather than stimulating
insulin secretion from βcells and results in
antihyperglycemic action rather than hypoglycemic
effect, i.e. does not affect normal blood sugar level,
which may be beneficial in case of misdosing.
Induction of diabetes with STZ is associated with the
characteristic loss of body weight, which is due to the
increased muscle wasting and loss of tissue proteins
(34). MELS administration to STZ diabetic rats
reversed the weight loss.
Serum enzymes including SGPT, SGOT and ALP are
used in the evaluation of hepatic disorders. An
increase in these enzyme activities reflects active liver
damage or inflammatory hepatocellular disorders (35).
In accordance with these findings, STZ induction has
a significant role in the alteration of liver functions
since the activities of SGPT, SGOT and ALP were
significantly higher than normal values. On the other
hand, treatment with MELS, like that with
glibenclamide, caused significant reduction in the
activities of these enzymes, showing the protective
effect of the extract.
Diabetes is associated with profound alteration in the
plasma lipid and lipoprotein profile and therefore is
associated with an increased risk of coronary heart
disease. Under normal circumstances, insulin activates
enzyme lipoprotein lipase and hydrolyses
triglycerides. Insulin deficiency results in failure to
activate the enzymes, thereby causing hyper-
triglyceridemia (36). The significant control of the
serum lipid levels in the MELS treated diabetic rats
may be directly attributed to the improvement in
insulin levels upon MELS treatment.
Hyperglycemia results in the generation of free
radicals, which can exhaust antioxidant defenses thus
leading to disruption of cellular functions, oxidative
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Diabetologia Croatica 40-2, 2011
P. Saha, U. K. Mazumder, P. K. Haldar, S. Kundu Sen, S. Naskar / ANTIHYPERGLYCEMIC ACTIVITY OF LAGENARIA SICERARIA
AERIAL PARTS ON STREPTOZOTOCIN INDUCED DIABETES IN RATS
damage to membranes and enhanced susceptibility to
lipid peroxidation, as reflected by the increased level
of lipid peroxide in the liver, pancreas and kidney
tissues of STZ control rats. A significant reduction of
this lipid peroxide level in MELS treated animals is
indicative of its ability to reduce body glucose
concentration and its subsequent oxidative damage.
GSH is normally present at high concentrations in the
cells and is a direct scavenger of free radicals, thereby
protecting the cells against the toxic effects of
oxidative stress. Antioxidant enzyme catalase (CAT) is
involved in detoxification of hydrogen peroxides and
thus protects the tissue from highly reactive hydroxyl
radicals. Diabetic animals in the present study showed
lowered levels of GSH and CAT in the liver, pancreas
and kidney tissues, reflecting the exhaustion of the
endogenous antioxidant defenses. Treatment with
MELS, however, increased both the reduced
glutathione content and CAT activity, and thus may
help avoid the free radical induced complications in
diabetes mellitus (35,37,38).
The above antihyperglycemic and antioxidant
properties of MELS were supported by the
comparative histopathologic studies of the pancreas,
liver and kidney tissues of diabetic control animals as
well as the extract and standard drug treated animals
(Figs. 2, 3 and 4).
In order to establish the relationship between the
chemical content and the antidiabetic activity, total
phenol and flavonoid contents of the extract were
determined and the results obtained from the
experiment revealed the high concentration of both the
phenolic and flavonoid contents. The beneficial effects
of several flavonol glycosides, rutin, quercetin,
anthocyanins, and various flavonoid rich extracts of
various plants are already known to have antidiabetic
activity, especially against type 2 diabetes mellitus
(39,40). These suggest that in the present study, there
can also be a correlation between the rich phenolic and
flavonoid contents of the extract and its potent
antidiabetic activity.
From the present investigation, therefore, it can be
concluded that MELS supplementation is quite
beneficial in controlling the blood glucose level,
without producing hypoglycemia; additionally, it
improves lipid metabolism and represents a protective
mechanism against the development of
atherosclerosis, and prevents diabetic complications
from lipid peroxidation by improving the antioxidant
status in experimental diabetic rats. Hence, the aerial
parts of L. siceraria methanol extract can be
considered as a potent source of antidiabetic agents,
which may be attributed to the flavonoid and
polyphenolic content of the extract. However, further
studies are ongoing to isolate the bioactive principle(s)
from it.
Acknowledgment
The necessary support and cooperation from Dr.
Abhijit Sen Gupta, Director-cum-Principal, and Prof.
Dipankar Chakraborty, Registrar, Guru Nanak
Institute of Pharmaceutical Science and Technology,
Kolkata, are gratefully acknowledged.
58
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AERIAL PARTS ON STREPTOZOTOCIN INDUCED DIABETES IN RATS
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