AJPSP 2012; Volume 3, Issue 1 Tarkang and Ofogba Page 17

AJPSP – FEBRUARY 19, 2012

Evaluation of the Hypoglycemic Activity and Safety of

Momordica charantia (Cucurbitaceae)

Protus Arrey Tarkang1*

, C. J. Ofogba2 (Late)

1Institute of Medical Research and Medicinal Plants Studies (IMPM), Yaoundé, Cameroon

2Dept of Biochemistry, University of Lagos, Nigeria

*Corresponding author email: ptarkang@yahoo.co.uk

ABSTRACT

Momordica charantia(MC) commonly called balsam pear or bitter melon has been implicated in

hypoglycemia and other pharmacological activities. Aqueous extract of the leaves of Momordica

charantia(MC) was tested for hypoglycemic activity by oral administration to both normal rats and

alloxan-induced diabetic rats for 28 days. Wistar rats were divided into 4 groups A, B, C, D. Group

A (control) was treated with intraperitoneal injection of the vehicle (saline alone), group B alloxan-

induced diabetic rats administered orally equal volumes of vehicle (distilled water) alone, group C,

normal rats and group D, alloxan-induced diabetic rats both administered 400mg/kg of the aqueous

extract. On the 29th

day, blood glucose, plasma insulin and the effect on Oral Glucose Tolerance Test

(OGTT) were monitored at 3, 6 and 9 h, for 50% of the rats of each group, while the rest of the rats

were sacrificed and the levels of certain biochemical parameters in the serum and examination of

some visceral organs were investigated.

At the end of the experiment, the blood glucose level of group C rats was found to have reduced

significantly (p<0.01) while there was no significant difference in the blood glucose level of group D

rats. Significant reduction in blood glucose during OGTT was observed in group D rats at 3, 6 and 9

h, compared to non treated diabetic rats. No changes were observed in plasma insulin levels,

indicating that the probable hypoglycemic mechanism involves improved glucose tolerance by

preventing glucose from being reabsorbed into the intestines. Highly significant increase in alkaline

phosphatase (p<0.001), AST and ALT (p<0.001) in alloxan-induced diabetic rats (B & D) and in

normal rats administered the aqueous extract, was observed, indicating liver hyperactivity.

Significant increases in creatinine clearance and a significant decrease in creatinine (p<0.01) in

group C suggest proper functioning of the kidneys.

Macroscopic examination of some visceral organs revealed profound pathological differences in

diabetic rats and normal rats administered the aqueous extract.

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The observed results indicate that Momordica charantia(MC) has strong hypoglycemic activity and

is safe for use as a therapeutic agent.

KEYWORDS: Momordica charantia, MC, Oral Glucose Tolerance Test, OGTT, hypoglycemic

activity, toxicity.

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INTRODUCTION

The use of herbs in therapy originated in

antiquity and most of its history is associated

with folklore. In as much as these herbs serve as

a potential source of food for human

consumption, a large number of their

preparations or remedies have been shown to be

particularly effective and standardized

proportions or extracts from them have been

incorporated into the practice of orthodox

medicine (1,2).

There is no doubt that modern therapeutics owes

a debt to traditional herbal remedies from

different parts of the world for the gift of

effective agents, e.g. atropine, coumarin

anticoagulants, glycosides, the ergot alkaloids,

the vinca alkaloids and quinine, just to mention

a few (3,4).

One of such important plants is Momordica

charantia(MC), commonly known as balsam

pear or bitter melon. Over the years, it has been

used in the preparation of various remedies for

numerous therapeutic purposes (5,6). It is a

climbing annual herb, of the Cucurbitaceae

family, usually found in moist and moderately

dry tropics such as the rain forest in West Africa

(7). It possesses undivided tendrils formed from

modified shoots, opposite leaves which are

circular and kidney-shaped and have five to

seven lobes, ovate to oblong in shape and

sometimes toothed along the margin. The plant

produces small irregular five lobed male and

female flowers of an orange yellow colour. The

inferior of the female flower develops into

oblong fruit with a bumpy surface. The fruit, a

berry hangs down on a slender stalk and is green

at first but later turns bright yellow. Inside are

pale gray to brown slightly flattened seeds with

a raised pattern on both sides. They are

surrounded by a blood red pulp, which forms a

striking contrast with the yellow coloured skin

of the fruit (8,9).

Investigations to evaluate the effect of MC on

the glucose tolerance showed that 75% of the

patients investigated responded (10,11). A

possible synergistic interaction in patients,

between a drug, chlorpropamide and a curry

made from MC and garlic, has been reported

(12). An improvement on the tolerance of

external load of glucose by non-insulin

dependent diabetics was reported by

Leatherdale et al., after oral administration of

50ml of MC fruit juice (13). A similar

observation was made by Athar et al., in

patients seven days after oral ingestion of

50mg/kg body weight of dried MC powder (14).

Furthermore, an insulin-like protein called

“plant insulin”, isolated from this plant, has

been shown to possess hypoglycemic properties,

when injected subcutaneously (15,16).

Treatment of diabetes aims at maintaining blood

glucose homeostasis, prevention of ketosis and

secondary complications. Major mode of control

is through diet and exercise, insulin replacement

therapy and by the use of oral hypoglycemic

agents (17,18). Most oral hypoglycemic agents

are Western drugs. Hypoglycemic herbs are

widely used as non-prescription treatment for

diabetes, though very few have been

standardized and their efficacy demonstrated in

systematic clinical trials as those of Western

drugs (19,20).

In supplementing the treatment of regimes of

orthodox medicine with herbal medicines, effort

should, however, be made to determine all the

active principles of the herbal product being

taken. It is a general belief held by most people

that herbal preparations are harmless and

ineffective but unfortunately, herbal products

could be exceedingly toxic e.g. Podophyllum

peltatum plant is neurotoxic and teratogenic

(2,21) Issues of standardization,

characterization, preparation, efficacy and

toxicity therefore, remain paramount and

necessitate careful supervision and monitoring

(22).

African Journal of Pharmaceutical Sciences and Pharmacy 2012;3:1

AJPSP 2012; Volume 3, Issue 1 Tarkang and Ofogba Page 20

This study aims at evaluating the hypoglycemic

activity and toxicity of the aqueous extract of

MC, with the view to ascertain its safety profile

and have some information on the mechanism

involved in the hypoglycemic action.

MATERIALS AND METHODS

Sample Collection and Extraction: Plant

material (MC) was purchased from the Mushin

Herbs market, Lagos-Nigeria after identification

by an herbalist and authentification by Dr.

Tsabang Nole, a botanist at IMPM. The leaves

were then air dried, pulverized by use of a

mechanic grinder and passed through 40-mesh

sieve to get the fine powder. 500g of the ground

material was then moistened appropriately with

distilled water and allowed to stand for

approximately 4h in a tightly closed container at

room temperature. The mass was then packed

into a percolator and distilled water added to

form a shallow layer just above the mass and the

percolator was closed. The mixture was allowed

to stand for 24h, after which the outlet of the

percolator was opened and the liquid contained

therein allowed to drip out completely. The

marc was then pressed and the liquid added to

the percolate, which was then freeze-dried,

weighed and kept in air-tight containers at 4oC

for further use. A weighed amount of the dried

aqueous extract was then dissolved in distilled

water to make a concentration of 400mg/kg

body weight (BW) for experimentation.

Animals: Healthy adult male albino rats of

Wistar Strain (180-200g) were divided into four

groups (A, B, C, and D) of 10 each and housed

in clean cages and maintained in a well

ventilated animal house. The animals were fed

with standard rat chaw and given clean drinking

water.

Experimental Design

Induction of Diabetes to Group B and D

Rats: After an overnight fast, rats were

administered intraperitoneal(i.p) injection of

120mg/kg BW of alloxan freshly dissolved in

saline (100mg/ml), to induce diabetic state with

a blood glucose level of more than 250mg/dl.

Blood glucose was monitored after alloxan

treatment to confirm the diabetic state and

diabetic rats were included in the experiment ten

days after treatment. Rats of all groups were

weighed prior to the experiment and daily

treatment was as follows for 28 days:

Group A: Control. Single i.p. injection of

vehicle (Saline alone).

Group B: Alloxan Diabetic. Oral administration

with equal volume of water alone.

Group C: Normal. 2ml 400mg/kg BW of

aqueous extract of MC.

Group D: Alloxan Diabetic. 2ml 400mg/kg BW

of aqueous extract of MC.

Biochemical and Histopathological Analysis:

At the end of the 28th

day, the animals are fasted

overnight and then 50% of the animals in each

group were sacrificed by cervical dislocation

and the serum collected for the analysis of some

biochemical parameters. Safety endpoints

included effects on serum glucose (GLU),

cholesterol (CHOL), triglycerides (TGY), urea

nitrogen (BUN), uric acid (URIC), creatinine

clearance (CCT), creatinine (CRE), alkaline

phosphatase (ALP), alanine transaminase (ALT)

and aspartate transaminase (AST). Some

visceral organs are also collected for

histopathological examination.

Oral Glucose Tolerance Test (OGTT): On the

29th

day after an overnight fast, blood was

collected from each of the remaining animals

for fasting blood glucose examination. An oral

dose of glucose (10ml/kg BW; 50%w/v) was

then administered to all the animals alongside

2ml 400mg/kg BW of the aq. extract of MC.

Blood glucose levels were then estimated with

time using a glucose kit (Menarini Diagnostics,

Italy), in which glucose oxidase and peroxidase

African Journal of Pharmaceutical Sciences and Pharmacy 2012;3:1

AJPSP 2012; Volume 3, Issue 1 Tarkang and Ofogba Page 21

enzymes are used along with chromogen 4-

aminophenazone and phenol, resulting in the

formation of a coloured compound that can be

measured at 500nm (Life Scan, USA) (23,24).

Radioimmunoassay of Insulin (RIA): Plasma

insulin was measured by the radioimmunoassay

Berthold Models LB2111 and LB2104 Multi-

Crystal Gamma Counter with Sodium Iodide 1-

1/8” × 1-1/4” Crystals as performed by the

Department of Child Health, University of

Missouri-Columbia, using Pharmacia Insulin

RIA kit (Pharmacia Diagnostics AB, Uppsala,

Sweden). RIA is a double-antibody batch

method. Insulin in the specimen competes with

a fixed amount of 125

I-labelled insulin for the

binding sites of the specific insulin antibodies.

Bound and free insulin are separated by adding

a second antibody, centrifuging and decanting.

The radioactivity in the pellet is then measured,

which is inversely proportional to the quantity

of insulin in the specimen (25,26,27). The test

is used to measure insulin levels in the

bloodstream and is also useful in determining

pancreatic β-cell activity.

African Journal of Pharmaceutical Sciences and Pharmacy 2012;3:1

AJPSP 2012; Volume 3, Issue 1 Tarkang and Ofogba Page 22

RESULTS

Table 1:

Results of Biochemical Tests on rats after treatment with aq. Extract of Momordica charantia for 28

days Dose

Mg/kg/

day

G GLU

mmol/l

CHOL

mmol/l

TGY

mmol/l

BUN

mmol/l

URIC

mmol/l

CCT

mmol/l

CRE

Umol/l

ALP

U/l

ALT

U/l

AST

U/l

Saline A 18.88 ±

0.28

18.12 ±

0.08

6.60 ±

0.52

18.40 ±

2.36

1.16 ±

0.08

142.80

± 1.44

170.24

± 4.08

326.48

± 6.72

68.68

± 3.04

90.52±

1.68

H2O B 26.32 ±

1.64

b

17.34 ±

2.20

6.62 ±

1.24

16.24

± 1.24

1.02 ±

0.02

102.80

± 3.24

196.74

± 2.84

426.96

± 3.41

a

144.20

± 7.41

a

164.96

± 5.40

a

400 C 5.56 ±

0.72

a

25.04 ±

5.80

5.76 ±

0.04

38.72

± 0.84

1.92 ±

0.04

284.80

± 1.76

127.74

± 3.16

329.56

± 6.92

74.44

± 4.72

102.88

± 6.29

400 D 19.42 ±

3,32

21.49 ±

2.17

6.71 ±

1.88

40.26 ±

2.49

2.01 ±

0.84

296.60

± 8.94

128.62

± 7.32

356.34

± 4.20

b

98.64

± 8.80

b

128.70

± 7.60

b

Results are means ± SD, n=4

Difference from control: Highly significant : a =

p<0.001; Significant : b = p<0.01

Key: GLU=Glucose, CHOL=Cholesterol,

TGY=Triglycerides, BUN=Blood Urea

Nitrogen, URIC=Uric Acid, CCT=Creatinine

Clearance Test, CRE=Creatinine,

ALP=Alkaline Phosphatase, ALT=Alanine

Transaminase, AST=Aspartate Transaminase.

G = Group; A = Group A (Control); B = Group

B (Diabetic); C = Group C (Normal); D =

Group D (Diabetic).

After 28 days of oral administration of the

aqueous extract, there was a highly significant

(p<0.001) decrease in blood glucose in normal

rats (group C) compared to the control as shown

in Table 1. At the same time there was a

significant (p<0.01) increase in non treated

diabetic rats (group B) whereas treated diabetic

rats showed no significant difference in blood

glucose level. A summary of the renal function

tests in Table 1 shows decreased values in

creatinine which correlates with increased

values in creatinine clearance test, as well as

blood urea nitrogen and uric acid in normal rats

compared to the control. This shows proper

functioning of the kidneys. Table 1 also shows a

highly significant (p<0.001) increase in ALP,

ALT and AST in diabetic rats, reflecting

hyperactivity of the liver and the cardiac

muscles, which might be due to the diabetic

condition.

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AJPSP 2012; Volume 3, Issue 1 Tarkang and Ofogba Page 23

Figure 1:

Effects of long term treatment of the aq. extract of Momordica charantia on Blood glucose levels of

male albino rats. Each histogram is mean of 5 rats.

Significant difference: a=p<0.01, b=p<0.05

Figure 2:

Effects of long term treatment of the aq. extract of Momordica charantia on plasma insulin of male

albino rats. Each histogram is mean of 5 rats.

No significant difference noticed.

0

5

10

15

20

25

30

0Hr 3hrs 6Hrs 9Hrs

Blo

od

Glu

cose

(m

g/d

l)

Time of Treatment

A. CONTROL(Saline)

B. DIABETIC(Water)

C. NORMAL ( 400mg/kg)

D. DIABETIC (400mg/kg)

a

a a

b

0

10

20

30

40

50

60

0Hr 3hrs 6Hrs 9Hrs

Pla

sma

In

suli

n (μ

U/m

l)

Time of Treatment

A. CONTROL

B. DIABETIC(Water)

C. NORMAL ( 400mg/kg)

D. DIABETIC (400mg/kg)

African Journal of Pharmaceutical Sciences and Pharmacy 2012;3:1

AJPSP 2012; Volume 3, Issue 1 Tarkang and Ofogba Page 24

Figure 3:

Effects of long term treatment of the aq. extract of Momordica charantia on blood glucose levels of

male albino rats.

Diabetic animals administered the extract behaved in the same manner as the control.

After long term administration of the aqueous

extract, examination of fasting blood glucose

revealed a significant decrease (p<0.05 and

p<0.01 respectively) in blood glucose in

diabetic rats (groups B and D) after 6 h of

observation whereas no significant difference

was observed in blood insulin even after 9 h as

shown in figures 1 and 2 respectively, in

correlation with the results obtained from the

biochemical assays.

Figure 3 shows that during Oral Glucose

Tolerance Test (OGTT), diabetic rats (Group D)

administered the aqueous extract after a glucose

load behaved in the same manner as the control.

There was a two fold increase in blood glucose

after 30 min of oral glucose load and at 60

through 90 min. There was a decrease up to 180

min when the blood glucose level came back to

normal. The blood glucose level in non-treated

diabetic rats (Group B) was, however,

significantly higher than the other groups and

the control after long term administration of the

aqueous extract. Upon administration of a

glucose load and then the aqueous extract

during OGTT, there was a threefold increase in

blood glucose level after 30 min, which

decreased to normal after 180 minutes.

Macroscopic examination of some visceral

organs revealed profound pathological

differences in diabetic rats and non diabetic rats

after administration of the aqueous extract of

MC as shown on the pathological plates of the

liver, kidney and heart of diabetic rats in figures

4, 5 and 6.

0

10

20

30

40

50

60

0Hr 30mins 60mins 90mins 180mins

Blo

od

Glu

cose

(m

g/d

l)

Time of sampling after glucose load

A. CONTROL(Saline)

B. DIABETIC(Water)

C. NORMAL ( 400mg/kg)

D. DIABETIC (400mg/kg)

African Journal of Pharmaceutical Sciences and Pharmacy 2012;3:1

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DISCUSSION

MC had been implicated in hypoglycemia

(28,29,30), and this was again confirmed in this

African Journal of Pharmaceutical Sciences and Pharmacy 2012;3:1

AJPSP 2012; Volume 3, Issue 1 Tarkang and Ofogba Page 26

study as shown in Table 1. This hypoglycemic

activity could be due to an increase in insulin

response or probably the transport of blood

glucose to peripheral tissues. Other causes of

hypoglycemia may include pancreatic lesions,

endocrine disease or some forms of liver or

kidney disorder (31). The renal function tests

indicated hyper function of the kidneys;

creatitine is removed from the plasma by

glomerular filtration and excreted in urine

without being reabsorbed by the tubules making

it a relatively accurate and useful measure of the

glomerular filtration rate (32). This correlates

with the decreased serum creatinine levels due

to high clearance rate and increased blood urea

nitrogen as a result of pre-renal causes such as

cardiac compensation, water depletion due to

increased intake or excessive loss (as observed

in excessive passing out of watery stool by the

experimental animals) and increased protein

catabolism (33). Apart from lowering the blood

sugar level in diabetic rats, there was no

difference in the level of ALP, ALT and AST in

diabetic rats administered MC extract from the

control, which indicates a potential of this plant

in protecting vital organs like the liver, hence a

probable strong antioxidant effect (34,35).

Whereas the aqueous extract of MC had a

significant hypoglycemic effect on blood

glucose levels, it had no significant effect on the

plasma insulin levels of diabetic rats. This non

significant change in plasma insulin levels does

not suggest the absence of any appreciable

stimulatory effect of the extract on the existing

β-cells of the endocrine pancreas in the diabetic

rats as earlier reported (36). Hafizur et al.

recently reported an increase in β-cell area and

number of β-cells in diabetic rats treated with

MC fruit extract as compared to the untreated

diabetic rats, thus confirming the pancreatic

modulatory effect of MC (37). This indicates

that the probable hypoglycemic mechanism

involves improved glucose tolerance by

preventing glucose from being re-absorbed into

the intestines and/or the existence of insulin-like

compounds in the extract (38). Biochemical

studies indicate that bitter melon regulates cell

signaling pathways in pancreatic β-cells

adipocytes and muscles (39). Clinical data

regarding the antidiabetic potentials calls for

better designed trials to further elucidate

therapeutic effects (40,41).

The tissue damage revealed by histopathology

in the diabetic rats as opposed to normal rats

reveals that administration of aq. Extract of MC

does not have any effect on the visceral organs

as shown on figures 4, 5 and 6. Drawing from

the results of the biochemical and the

histopathological analysis of this study, as well

as earlier studies on toxicity (42), we can

confirm the safety of the aqueous extract of MC.

In conclusion, MC possesses a modest

hypoglycemic and antioxidant activity and this

study provides evidence for a biochemical

mechanism which carries blood glucose

lowering effect of MC. Since earlier studies

have demonstrated its dietary quality and safety,

it can be recommended for the management of

diabetes. Further studies on the nature of active

principles involved would be of immense

importance.

African Journal of Pharmaceutical Sciences and Pharmacy 2012;3:1

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