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International Journal of Medicine and Biomedical Research
Volume 1 Issue 3 September – December 2012
www.ijmbr.com
© Michael Joanna Publications
Original Article
Int J Med Biomed Res 2012;1(3):232-241
232
Antioxidant effect of unripe plantain (Musa paradisiacae) on
oxidative stress in alloxan-induced diabetic rabbits
Eleazu C.O1* and Okafor P.N2
1Department of Biochemistry, National Root Crops Research Institute, Umudike, Umuahia, Abia
State, Nigeria. 2Department of Biochemistry, Michael Okpara University of Agriculture, Umudike,
Umuahia, Abia State, Nigeria.
*Corresponding Author: eleazon@yahoo.com
Received: 24.09.12; Accepted: 25.10.12
ABSTRACT
Background: Diabetes mellitus results in complications that could be
contributed by elevated levels of free radicals and oxidative stress and
increased risk of cardiovascular disease. Aim: We investigated the effect
of the antioxidant activity of unripe plantain on oxidative stress markers in
alloxan induced diabetic rabbits. Materials and Method: Rats were
randomized into three groups; control, diabetic, and unripe plantain-
treated diabetic rats. The proximate, phytochemical and antioxidant
activity of the unripe plantain were determined. The glutathionine,
malonaldehyde, catalase and glucose levels of the animals were also
determined using standard techniques. Result: The diabetic rabbits
placed on unripe plantain diet had a decrease in their blood glucose (-
24.25±8.08%) and malonaldehyde levels with a corresponding increase in
their weights (23.63±1.20%), glutathione and catalase levels after 3weeks
of dieting compared with the control (p<0.05). Glutathione correlated
negatively with malonaldehyde and glucose (r = -0.77 and -0.877), but
positively with catalase and body weight (r = 0.60 and 0.70).
Malonaldehyde correlated negatively with catalase and body weight (r = -
0.44 and -0.72) but positively with glucose (r = 0.86). Catalase correlated
negatively with glucose(-0.69) but positively with body weight (1). The
extract had a high scavenging activity on DPPH radical (78.57±0.12%)
comparable to that of standard vitamin C (83.20±0.00%) in addition to a
high total antioxidant activity (62±0.20%). The flour contained low
amounts of protein, lipid, tannin, saponin, alkaloids, flavonoids and energy
value but significant quantities of crude fibre, ash and carbohydrates.
Conclusion: These findings suggest that raised blood glucose level in
diabetics could deplete cells of their antioxidant status with resultant
increase in oxidative stress. Finally, unripe plantain intake may exert a
free radical scavenging activity by ameliorating the altered antioxidant
status.
Key words: Diabetes, rabbits, plantain, oxidative stress, antioxidant
INTRODUCTION
Diabetes mellitus, a metabolic disease
associated with hyperglycemia, is thought to
arise either from a deficiency of pancreatic β-
cells (as a result of an autoimmune disorder
which destroys the pancreas to produce type 1)
or insulin resistance which may be due to a
number of defects in signal transduction ranging
from abnormal insulin or insulin receptors to
defects in glucose transporters (GLUT 4, which
produces type 2) resulting in elevated blood
glucose levels.[1] In the year 2002, about 173
million people suffered from diabetes mellitus.
About two thirds of these people lived in
Eleazu and Okafor: Antioxidant and antidiabetic effect of unripe plantain (Musa paradisiacae)
Int J Med Biomed Res 2012;1(3):232-241
233
developing countries, making it endemic in these
countries.
There are reports that about 150 million people
worldwide have diabetes mellitus, and this
number may be double by 2025.[3,4,5] In recent
studies, some evidence suggest that oxidative
stress may play some role in the etiology of
diabetes and its complications.[5] Nourooz-zadeh
et al.[6] has reported an altered balance between
Reactive Oxygen Species (ROS) production and
antioxidants. Though insulin therapy is used for
the management of the disease, there are still
draw backs like insulin resistance,[7] as well as of
its high cost which are not affordable in the poor
economic community. In addition, the drugs that
are being used in the management of the
disease such as sulphonylureas, metformin and
acarbose (novel) have been associated with
serious side effects such as: weight gain,
hypertension, hepatic impairment and renal
impairment. This has increased the research
into medicinal plants with anti-diabetic potentials
mostly because the herbal drugs are considered
to be less toxic with fewer side effects compared
with synthetic drugs.[8,9,10]
In addition, dietary management of diabetes has
been helpful and such diets that are used in the
management of diabetes include: acha, beans,
breadfruit and in Nigeria, unripe plantain diet.
However the mechanism by which unripe
plantain ameliorates diabetes mellitus has not
been fully investigated. There are indications
that this could be through antioxidant activity
since some of the phytochemical constituents
could serve as antioxidants. Also the unripe
plantain could have a low glycemic response
when consumed. This work is aimed at
investigating the above.
MATERIALS AND METHODS
Plant materials
Unripe plantain that was used was bought from
the local market in Umuahia, Abia State, Nigeria.
It was thoroughly washed, peeled and freeze
dried in a freeze drier for 48 h.
Preparation of plant materials for
analysis
A measured quantity of the unripe plantain
(100g) was ground into flour using a food
processor and the flour was then used for
analysis.
Chemicals
Alloxan, Malonaldehyde derivative (1,1,3,3
tetraethoxypropane), Stock Glutathione, DPPH
(2,2-diphenyl-1-picrylhydrazyl) and Peroxidase
that were used were products of Sigma and
Aldrich Chemical Company (UK). All other
chemicals that were used for the animal
experiments were bought from Associated
Laboratories, Aba, Nigeria and were of analytical
grade.
Preparation of plant extract for
antioxidant and DPPH (2,2-diphenyl-1-
picrylhydrazyl) radical scavenging
assays
Unripe plantain flour (1 g) and methanol (20 ml)
were thoroughly mixed and left over night. The
mixture was then filtered (Whatman No. 1 filter
paper). The filtrate was made up to 25ml with
methanol. The methanolic unripe plantain
extract (40 mg/ml) was diluted to suitable
concentrations of 250, 125, 62.5, 31.25 and
15.62 µg/ml which were used for the DPPH
radical scavenging test, while the concentrations
of 10, 20, 30 and 40 mg/ml were used for total
antioxidant activity assays.
Proximate composition of unripe
plantain flours
The percentage moisture, crude protein, crude
fibre, crude fat and total carbohydrates were
analyzed according to the AOAC methods.[11]
The values reported are means of triplicate
samples with their standard deviations.
Phytochemical composition of unripe
plantain flour
The gravimetric method of Harbone [12] was used
in the determination of the total alkaloid content
while the AOAC method [13] was used in the
determination of other phytochemical
constituents of the sample.
Assay of DPPH radical scavenging
activity
The free radical scavenging activity of the
plantain extract was determined using the
method of Blois [14] with modifications. One ml of
different concentrations (500, 250, 125, 62.5,
31.25 µg/ml) of extracts and standard vitamin C,
were added to 1 ml of 0.3 mm DPPH in
methanol to bring the final concentration of 250,
Eleazu and Okafor: Antioxidant and antidiabetic effect of unripe plantain (Musa paradisiacae)
Int J Med Biomed Res 2012;1(3):232-241
234
125, 62.5, 31.25 and 15.62 µg/ml. The mixture
was vortexed and incubated in a dark chamber
for 30 min and the absorbance was read at 517
nm against a DPPH control that contained 1 ml
of methanol. The percentage scavenging activity
was calculated as:
% Scavenging activity =
Absorbance of control –Absorbance of sample x 100
Absorbance of control
Assay of total antioxidant activity
The total antioxidant activity was measured
according to the method described by Hsu et
al.[15] by determining the scavenging activity of
the extract on ABTS (2,2-azino-bis(3-ethylbenz-
thiazoline-6-sulfonic acid) radical. A measured
quantity (0.2 ml) of peroxidase (4.4units/ml) +
0.2 ml of H2O2 (50 µM) + 0.2 ml ABTS ((2,2-
azino-bis (3-ethylbenz-thiazoline-6-sulfonic acid,
di-ammonium salt, 100 µm) + 1 ml distilled water
were mixed together and left in the dark to form
a bluish green complex. After adding 1 ml of
methanolic plantain flour extract, the absorbance
was measured at 734 nm to represent the total
antioxidant activity. The total antioxidant activity
was calculated as follows:
Total antioxidant activity =
1 – (Absorbance of sample ) x 100
Absorbance of control
Experimental animal
Ten matured male rabbits weighing between
1.58 and 1.88 kg were used for this experiment.
Animals were acclimatized for a period of 7 days
to the laboratory conditions prior to the
experiment in line with the University’s ethics of
animal experiments. Rabbits were housed in
well ventilated colony cages with 2 rabbits per
cage at room temperature (27-30oC) with 12 h
light and dark cycle and they had free access to
drinking water and their diets (ad libitum).
Induction of diabetes
Rabbits were fasted for 24 h before injection of a
freshly prepared solution of alloxan intra-
peritoneally at a dosage of 35 mg/kg body
weight. This single dose of alloxan produced
type 1 diabetes having fasting blood sugar level
of 195±10.71 mg/dl after 7 days of injection of
alloxan and this diabetic state was maintained
throughout the duration of the experiment.
Experimental procedure
The rabbits were divided into 3 groups as
follows:
(Group 1) Non-diabetic control: The animals of
this group received commercial rabbit feeds
comprising of crude protein, fat, crude fibre,
calcium, phosphorous, Lysine, Methionine and
salt for 2 weeks (Table 5). Their body weights,
malonaldehyde, glutathione, catalase and blood
sugar levels were recorded on the 1st and last
week of the experiment and their means were
reported.
(Group 2) Diabetic control:
At the expiration of 2 weeks, alloxan was
injected intraperitoneally into the control group
and they formed group 2 animals. The animals
were confirmed to be diabetic after estimation of
their blood glucose levels using a single touch
glucometer, 7 days after injection of alloxan. An
animal was considered to be diabetic if it had a
fasting blood sugar level > 130 mg/dl. The
animals of this group also received commercial
rabbit feeds comprising of crude protein, fat,
crude fibre, calcium, phosphorous, lysine,
methionine and salt for 2 weeks (Table 5). Their
body weights, malonaldehyde, glutathione,
catalase and blood sugar levels were also
recorded on the 1st and last week of the
experiment.
(Group 3) Diabetic rabbits + unripe plantain flour
(test groups):
At the expiration of 2 weeks of induction of
diabetes into the animals of group 2, they were
force fed with unripe plantain flour for a period of
3 weeks and they thus formed the animals of
group 3. Their blood glucose, body weights,
malonaldehyde, glutathione, catalase and blood
sugar levels were also recorded on the 1st, 2nd
and last week of the experiment. Similarly, the
initial and final body weights were measured
with an electronic weighing balance. From
these, the percentage fasting blood glucose
reduction and percentage weight change were
calculated using the formula:
The percentage change in weight =
Initial weight- Final weight x 100
Initial weight
The percentage growth rate was calculated as:
Final weight- Initial weight x 100
Experimental duration
The percentage change in fasting blood glucose
was calculated as:
Initial fasting blood glucose level-Final fasting blood glucose level
Initial fasting blood glucose level x 100
Eleazu and Okafor: Antioxidant and antidiabetic effect of unripe plantain (Musa paradisiacae)
Int J Med Biomed Res 2012;1(3):232-241
235
Determination of malonaldehyde (MDA)
The method of Health and Parker [16] was used
with slight modification. A measured amount (0.2
ml) of blood plasma was added to 3 ml of glacial
acetic acid followed by 3 ml of thiobarbituric acid
solution. The mixture was placed in boiling water
for 15 min, allowed to cool before being read
spectrophotometrically at 532 nm.
Preparation of thiobarbituric acid (TBA)
Two percent (2%) sodium hydroxide was
prepared by dissolving 2g of sodium hydroxide
in 100 ml of water. Then 1% TBA was prepared
by dissolving 1g of TBA in the 100 ml of the 2%
sodium hydroxide. The standard curve was
plotted using the MDA derivative (1,1, 3, 3
tetraethoxypropane).
Determination of whole blood
glutathione
This was measured using the method of Duron
and Kelly.[17] The principle is based on the
determination of reduced glutathione in each
dilution by the measurement of the absorbance
of colored solution developed within 5 min of the
generation of Elman’s reagent at 430 nm
wavelength.
Determination of plasma glucose
The principle of oxidation of β-D glucose to β-D
glucono 1, 5 lactone with the release of
hydrogen peroxide by glucose oxidase which
later hydrolyses gradually to β-D gluconic acid
was employed using a Randox kit for the assay.
The absorbance of the mixture was measured at
625 nm using ortholidine as the color reagent.
Determination of red cell catalase
activity
The principle of Cohen et al.[18] was made use of
here by monitoring the rate of enzyme catalyzed
decomposition of hydrogen peroxide (H2O2)
using potassium tetraoxomanganateVII
(KMnO4). Fifty µl of sample was added to a test
tube. H2O2 was then added to the tube and
incubated on ice for 3 min. Then, H2SO4 was
used to stop the reaction. Finally, KMnO4 was
added and the absorbance was recorded at 480
nm.
In this assay, 1unit of enzyme activity = K
0.00693
Where K = Log So x 2.3
S2 t
So = Absorbance of standard - absorbance of
blank, S2 = Absorbance of standard-absorbance
of sample. T = Time interval. The measured
activities were normalized with the protein
content of each sample.
Statistical analysis
Data was subjected to analysis of variance using
the statistical package for social sciences
(SPSS), version 15.0. Results are presented as
mean ± standard deviations. One way analysis
of variance (ANOVA) was used for comparison
of the means. Differences between means were
considered to be significant at P < 0.05 using the
Duncan Multiple Range Test. Values are
average of triplicate experiments ± standard
deviation.
RESULTS
The proximate composition of the unripe
plantain flour as determined in this study
indicated that it contained 5.5±0.42% ash,
39.04± 4.51% carbohydrate, 3.15± 0.04%
protein, 0.21 ± 0.03% lipid, 6.20± 1.95% crude
fibre, 52.0 ± 2.80% moisture and energy value of
170.65 ± 17.44 (Kcal/100g) (Table 1).
Table 1: Proximate composition of unripe
plantain flour
Proximate analyzed
Percentage
composition
Ash
5.50 ± 0.42
Carbohydrate
39.04 ± 4.51
Protein
3.15 ± 0.04
Lipid
0.21 ± 0.03
Crude fibre
6.20 ± 1.95
Moisture
52.0 ± 2.80
Energy value
170.65±17.44
(Kcal/100g)
The phytochemical analysis of the flour indicated
that it contained 1.577 ± 0.04% tannin, 1.37 ±
0.05% alkaloid, 1.827 ± 0.05% saponin and
0.981 ± 0.00% flavonoid (Figure 1).
The flour had 78.57±0.06% inhibitory action on
DPPH radical comparable to that of vitamin C
(82.50±0.00) while it possessed a significant
total antioxidant activity in addition (62 ± 0.20%)
(Tables 2 and 3).
Eleazu and Okafor: Antioxidant and antidiabetic effect of unripe plantain (Musa paradisiacae)
Int J Med Biomed Res 2012;1(3):232-241
236
Analysis of the nutritive constituents of the
commercial feed that were administered to the
rabbits indicated that it contained 18% Protein,
6% Fat, 5% Crude fibre, 1% Calcium, 0.4%
Phosphorous, 0.85% Lysine, 0.34% Methionine
and 0.3% salt (Table 4).
Table 2: Inhibitory action on DPPH radical
Sample
Percentage inhibition
Unripe plantain flour
78.57±0.06
Vitamin C
82.50±0.00
Table 3: Total antioxidant activity of unripe
plantain flour
Sample
Activity
Unripe plantain flour
62 ± 0.20%
Table 4: Nutrient composition of the feeds
administered to the rabbits
Nutrient
Percentage composition
Crude protein
18.00
Fat
6.00
Crude fibre
5.00
Calcium
1.00
Phosphorous (available)
0.40
Lysine
0.85
Methionine
0.34
Salt
0.30
The results of the animal experiments that were
carried out indicate that the mean value of
glutathione (GSH) in the diabetic animals were
lower than that of the non-diabetic animals.
Unripe plantain intake by the diabetic animals
significantly improved their glutathione status
(Table 5).
There was a significant elevation in the
concentration of the plasma malonaldehyde of
the diabetic rabbits compared with the control.
This parameter was significantly ameliorated
after administration of unripe plantain to the
diabetic animals (Table 5).
There was a significant depletion of the red cell
catalase activity of the diabetic rabbits compared
with the non-diabetic. However, administration of
unripe plantain flour to the diabetic animals
resulted in a significant amelioration of their
catalase activity (Table 5).
There was a significant elevation in the fasting
blood glucose levels of the rabbits after
administration of a single dose of alloxan.
Administration of unripe plantain flour to the
diabetic animals resulted in significant
amelioration of their blood glucose levels (Table
5).
The weights of the animals depreciated after
administration of alloxan. This parameter
however, was significantly ameliorated after the
administration of unripe plantain flour (Table 5).
Table 5: Indices of oxidative stress in diabetic
rabbits.
Parameter
Non-diabetic
rabbits
(control)
Diabetic
rabbits
Diabetic
rabbits
+
plantain flour
GSH(mg/ml)
61.08±11.16a
27.09±3.18b
48.09±9.39a
MDA(mg/ml)
0.12±0.02a
0.44±0.15b
0.129±0.02a
Catalase
(µmol/min/ml)
51.78±11.15a
26.65±11.32b
40.05±10.74a
Glucose(mg/dl)
55.51±12.65b
155.8±10.71a
68.4± 12.58b
Weight(Kg)
1.73 ± 0.15b
0.86± 0.05a
1.32±0.10b
Values with the same superscript along each row are
not significantly different (P > 0.05). (N = 10).
GSH – Glutathione MDA – Malonaldehyde
There was a 23.63±1.20% and 5.86±1.01%
increase in weights and growth rates
respectively with a corresponding decrease in
fasting blood glucose level (-24.25±8.08) after
administration of unripe plantain flour to the
diabetic animals (Table 6).
Eleazu and Okafor: Antioxidant and antidiabetic effect of unripe plantain (Musa paradisiacae)
Int J Med Biomed Res 2012;1(3):232-241
237
Correlation analysis carried out revealed that
glutathione correlated negatively with glucose
and malonaldehyde (R2 = -0.877 and -0.771),
but positively with catalase and body weight (R2
= 0.601 and 0.700) (Table 7). Malonaldehyde
correlated positively with glucose (R2 = 0.863),
but negatively with catalase and body weight (R2
= -0.443 and -0.720) (Table 8). In addition, there
was a negative correlation between catalase
and glucose (-0.69), but positive correlation
between catalase and body weight (R2 = 1)
(Table 9).
Table 6: Percentage change in glucose,
weight and growth rate
Weight
23.63±1.20
Growth rate
5.86±1.01
Fasting blood
glucose (decrease)
-24.25±8.08
Table 7: Correlation between glutathione
versus catalase, malonaldehyde (MDA),
glucose and weight
Glucose
MDA
Catalase
Weight
Glutathione
-0.877**
-0.771*
0.601
0.700**
** Highly significant at 0.01 level
Table 8. Correlation between malonaldehyde
(MDA) versus catalase, weight and glucose
Glucose
Catalase
Weight
MDA
0.863**
-0.902**
0.720*
** Highly significant at 0.01 level
Table 9. Correlation between catalase
versus glucose and weight
Glucose
Weight
Catalase
-0.690
1
DISCUSSION
The proximate composition of the unripe
plantain flour as determined in this study,
showed that it contained significant quantities of
ash which reflects the mineral contents of the
plantain. The low fat contents of the flour as
observed in this study were in accordance with
previous reports.[19]The low crude protein
content obtained in the plantain flour were also
in accordance with previous studies.[20] Since a
healthy adult needs about 0.75g of protein per
kg per day, plantains alone cannot meet adult
protein diet. The moderate amount of
carbohydrate that was obtained in the unripe
plantain flour indicates that the flour could have
a low glycemic index when consumed. Similar
results have been reported by Ahenkora et al.[21]
Dietary fibre is increasingly being recognized as
a useful tool for the control of oxidative
processes in food products and as functional
food ingredient. In addition, dietary fibre
decreases the absorption of cholesterol from the
gut in addition to delaying the digestion and
conversion of starch to simple sugars, an
important factor in the management of diabetes.
Dietary fibre also functions in the protection
against cardiovascular disease, colorectal
cancer and obesity. Thus the high fibre contents
of the unripe plantain flour, as observed in this
study, infer that unripe plantain could be
effectively utilized in the management of
diabetes mellitus, colorectal cancers and weight
reduction in obesed individuals and this is an
important finding in this study. This finding could
be one explanation behind the hypoglycaemic
action of the flour that was obtained in this work.
The moisture content of the flour was observed
to be high, indicating that the flour may have
poor shelf life characteristics in addition to
prevalence to microbial attack. The energy value
of the flour which was calculated by multiplying
the percentage carbohydrate content by 4, fat by
9 and protein by 4,[13] indicates that unripe
plantain cannot be classified as a high energy
food as the energy value was observed to be
low.
The flour was observed to contain significant
quantities of saponins, flavonoids, tannins, and
alkaloids. Saponins are known to possess both
beneficial (cholesterol lowering) and deleterious
(cytotoxic permeabilization of the intestine)
properties.[22] However, the levels of saponin in
the flour are quite too low to cause any
deleterious effects. Flavonoids, alkaloids and
tannins are polyphenolic compounds with
antioxidant properties. Phenolics are secondary
plant metabolites, and are widely spread
throughout the plant kingdom. They have been
Eleazu and Okafor: Antioxidant and antidiabetic effect of unripe plantain (Musa paradisiacae)
Int J Med Biomed Res 2012;1(3):232-241
238
associated with colour, sensory qualities, and
nutritional and antioxidant properties of food in
addition.[23] It has been reported that phenolic
compounds in plants possess antioxidant activity
and may help protect cells against the oxidative
damage caused by free radicals.[24] The present
study shows that unripe plantain flour contains
some amounts of polyphenols and this implies
that it may be useful in relation to diseases
involving free radical reactions.
The DPPH assay is a widely accepted method
for the determination of the antioxidant activities
of various food substances. This is because,
DPPH is a stable free radical in methanol or
aqueous solution and accepts an electron or
hydrogen radical to turn into a stable
diamagnetic molecule, in addition to producing a
strong absorption band at 517 nm in the visible
region of the electromagnetic radiation. The high
scavenging activity of the methanolic extract of
the unripe plantain flour on DPPH radical is a
major significant finding in this study. This is
attributable to the polyphenolic contents of the
plantain flour.
The DPPH assay has the limitation of color
interference and sample solubility [25,26] and this
informed the assay of the scavenging activities
of the extract on ABTS as the ABTS/H2O2/HRP
discoloration has been reported to represent the
total antioxidant activity of methanolic extracts of
a variety of food substances.[16] In addition, the
ABTS assay is also stable and does not suffer
from color interference. The antioxidant activity
of the methanolic extract of the unripe plantain
flour as determined in this study shows that the
extract possesses a remarkable antioxidant
activity and this was expected since analysis
showed that it contained flavonoids and
alkaloids which are high potency antioxidants
with free radical scavenging activities. Results
obtained show that unripe plantain flour could be
a potential source of natural antioxidants that
could be of medicinal purposes in the treatment
of ailments implicating free radicals and
oxidative stress.
Alloxan is known to destroy the ß-cells of the
islets of the langerhans of the pancreas that
function in the regulation of insulin secretion and
thus leads to an increase in the concentration of
blood glucose. However, this parameter was
decreased significantly in the diabetic rabbits
that were placed on unripe plantain diet. Our
results agree with the earlier reports of Ojewole
and Adewunmi [27] and Gomathy et al.[28] on the
hypoglycemic action of unripe plantain. Chhanda
et al.[29] have also reported that diminished
serum insulin level in streptozotocin induced
diabetic rats was recovered significantly after co-
administration of methanolic extracts of Euglena
jambolana and Musa paradisiaca. The
ameliorating effect of the unripe plantain flour on
hyperglycemia in the diabetic animals can be
explained from 2 perspectives: First, it was
found to contain significant quantities of crude
fibre as earlier mentioned. Dietary fibre
decreases the absorption of cholesterol from the
gut in addition to delaying the digestion and
conversion of starch to simple sugars and this is
an important factor in the management of
diabetes. Secondly, the flour was found to
contain tannins, saponins, alkaloids and
flavonoids which are polyphenolic compounds.
Polyphenols are products of the secondary
metabolism that originate from 2 main synthetic
pathways; the Shikimic acid and/or the acetate-
malonate pathways, both of which are derived
from glucose metabolism in plants. Some
polyphenols such as tannins inhibit the activity of
digestive enzymes such as trypsin and amylase.
The inhibition of glycolytic activity of brush
border enzymes by polyphenolic compounds
seems to be one of the factors that stimulates
hypoglycemic action in some medicinal plants.
In addition, flavonoids, as antioxidants may
prevent the progressive impairment of
pancreatic beta cell function due to oxidative
stress, thereby reducing the occurrence of
diabetes. Thus it’s plausible to infer that these
crude fibre and phytochemicals could through
synergistic interactions, ameliorate the
hyperglycemia that resulted from the diabetes in
the animals.
The depletion in the glutathione status of the
diabetic animals is attributable primarily to the
alloxan (a xenobiotic) that was injected into the
rabbits. Both xenobiotics and normal metabolism
are known to deplete antioxidants as they are
consumed in the course of scavenging reactive
species generated. The depletion in glutathione
to the level that was observed in this work could
lead to a devastating decrease in the total
antioxidant status of the animals because
glutathione helps in recycling cellular
antioxidants, inhibits free radical damage and
plays a key role in the detoxification of harmful
compounds.This agrees with earlier works
carried out by Dominquez et al.[30] and Polidori et
al.[31] who reported a reduced total plasma
Eleazu and Okafor: Antioxidant and antidiabetic effect of unripe plantain (Musa paradisiacae)
Int J Med Biomed Res 2012;1(3):232-241
239
antioxidant capacity in uncontrolled diabetes.
However, administration of unripe plantain to the
diabetic rabbits resulted in significant
amelioration of their glutathione status and this
is remarkable as this implies that unripe plantain
diet could have an ameliorating effect on the
altered antioxidant status of a diabetic.
The elevation in the malonaldehyde levels of the
diabetic animals is also attributed to the alloxan
that was injected into the rabbits. Ceriello et
al.[20] reported that diabetic patients show during
the postprandial period, an increase in plasma
malonaldehyde levels. However, the diabetic
rabbits, when placed on unripe plantain diet also
remarkably had a decrease in their plasma
malonaldehyde levels compared with the
control, indicating the free radical scavenging
activity of unripe plantain on oxidative stress in
diabetics.
The depletion of whole blood catalase activity
after injection of alloxan is another significant
finding in this study. The decreased
concentration of red cell catalase is attributable
in part to the reduced synthesis of this
antioxidant enzyme (which functions in the
detoxification of hydrogen peroxide) whose
concentrations would have fallen with the
alloxan that was injected into the animals. Some
studies have reported no alterations in the
activity of red cell catalase in diabetics.[32]
However, the results we obtained are in
agreement with earlier reports of Udoh, et al.[33]
and Tagami, et al.[34] who reported a decreased
red cell catalase activity in diabetics. It is
important to note at this point that the drastic
decrease in the antioxidant status of the body
could precipitate “oxidant stress” with a
concomitant attack of reactive oxygen species or
free radicals on cells of some target tissues or
organs of the body. However, the diabetic
rabbits placed on unripe plantain diet had an
increase in their catalase concentrations and
this again indicates the ability of unripe plantain
diet to ammeliorate the altered antioxidant status
of diabetics.
The loss in weight by the diabetic animals was
expected as one of the effects of diabetes is
body weight loss. With the destruction of the
pancreatic cells by alloxan, there’s deficiency of
insulin leading to increased synthesis of ketone
bodies which are excreted in urine. The
increased synthesis of ketone bodies coupled
with increased lipolysis leads to a severe loss of
weight. However, the diabetic rabbits placed on
unripe plantain diet had a remarkable gain in
body weight.
The study shows the place of proper dieting in
the management of diabetes. This is because, in
addition to drug therapy, proper diet is critical in
the management of diabetes mellitus. Such diets
should be balanced and nutritious, ensuring
normal growth and development, in addition to
attainment of the ideal body weight. We
recorded an appreciable increase in weight and
glucose reduction in the diabetic rabbits fed
unripe plantain flour but a low increase in growth
rate, which is attributable to the fact that the
rabbits that were used for the study were
matured ones. In addition, the flour was found to
be low in proteins which are needed for growth
and repair of the tissues.
The study shows that raised blood glucose in
diabetics could deplete cells of their antioxidant
status with concomitant increase in free radicals
thereby precipitating oxidative stress. Finally, the
high correlation recorded between red cell
catalase and body weight of the animals,
indicates that regular intake of antioxidant foods
by diabetic could go a long way in ameliorating
their altered body weights that could arise from
complications of diabetes such as altered
protein metabolism and this underscores the
need for the administration of antioxidant rich
foods in the diet of diabetics.
CONCLUSION
The free radical scavenging activity of unripe
plantain in diabetics has been demonstrated in
this study. There are indications that unripe
plantain flour mimics insulin action by binding to
specific receptors in the cell membrane of
tissues (in a way similar to insulin) possibly at
the α-subunits of receptors that are transduced
to the β-subunits, promoting the rapid
autophosphorylation of a specific tyrosine
residue of each β-subunit and inducing a
conformational change, one of which is
decreased oxidative stress through the
restoration of altered antioxidant status. This is
approached from a biochemical point of view
and is subject to further confirmation.
In addition, it has been found to be a good
source of antioxidants and this property could be
included to the purpose for which its been
utilized in diabetics.
Eleazu and Okafor: Antioxidant and antidiabetic effect of unripe plantain (Musa paradisiacae)
Int J Med Biomed Res 2012;1(3):232-241
240
ACKNOWLEDGEMENT
The authors are grateful to Mr Arukwe of
Biochemistry Department, Abia State University
Uturu, Mr Egbuedo of Soil Science Department,
Michael Okpara University of Agriculture,
Umudike, Umuahia, Abia State and Dr and Mrs
I.N. Eleazu who contributed in one way or the
other to make this work a success.
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doi: http://dx.doi.org/10.14194/ijmbr.1311
How to cite this article: Eleazu C.O and
Okafor P.N. Antioxidant effect of unripe
plantain (Musa paradisiacae) on oxidative
stress in alloxan induced diabetic rabbits.
Int J Med Biomed Res 2012;1(3):232-241
Conflict of Interest: None declared
