Antihyperglycemic Activity of Moringa oleifera Lam Leaf Functional Tea in Rat Models and Human Subjects

Full text

Food and Nutrition Sciences, 2016, 7, 1021-1032
http://www.scirp.org/journal/fns
ISSN Online: 2157-9458
ISSN Print: 2157-944X
DOI: 10.4236/fns.2016.711099 September 23, 2016
Antihyperglycemic Activity of Moringa oleifera
Lam Leaf Functional Tea in Rat Models
and Human Subjects
Edith N. Fombang*, Romuald Willy Saa
Department of Food Science and Nutrition, National School of Agro-Industrial Sciences (ENSAI), University of Ngaoundere,
Ngaoundere, Cameroon
Abstract
Maintenance of glycemic control is important in preventing diabetes and its ass
o-
ciated complications. Considering the current recommended approach for the use of
functional foods and their bioactive components in the prevention and management
of diabetes, the aim of this study was to determine the antihyperglycemic effect of
Moringa oleifera
functional tea in rat models and in normoglycemic human volu
n-
teers using the oral glucose tolerance test (OGTT). Moringa tea prepared by extrac
t-
ing Moringa leaf powder in distilled water (1:20 mg/ml) at 97˚C for 30 min was a
d-
ministered at different doses to male Wistar rats and human volunteers prior to gl
u-
cose loading. Blood glucose was measured at intervals of 30 min for 150 min. Co
n-
sumption of Moringa tea prior to glucose loading suppressed the elevation in blood
glucose in all cases compared to controls that did not receive the tea initially.
The
degree and pattern of decrease however, were dose
dependent. In rats, intermediate
doses of 20 ml/kg BW were more effective in reducing blood glucose overall (18.2%)
vs 13.3% and 6% at doses of 10 and 30
ml/kg BW respectively. In humans, the final
decrease in blood glucose was not significantly different for high 400 ml (19%) and
low 200 ml (17%) doses. Of interest here was the pattern of decrease, being signif
i-
cantly higher (p < 0.05) at 30 min with 200 ml (22.8%) than with 400
ml (17.9%). It is
suggested that low doses exert their antihyperglycemic effect more at intestinal level
by inhibiting glucose absorption, whereas high doses exert their effect more in circ
u-
lation. We conclude that
Moringa oleifera
tea has potential as a functional food in
the management of hyperglycemia.
Keywords
Moringa oleifera
Functional Tea, Antihyperglycemic Activity, Phenolic Compounds
,
Antioxidant Activity, Humans, Rats
How to cite this paper: Fombang, E.N. and
Saa, R.W.
(2016) Antihyperglycemic Acti
v-
ity of
Moringa oleifera
Lam Leaf Functional
Tea in Rat
Models and Human Subjects
.
Food
and Nutrition Sciences
,
7
, 1021-1032.
http://dx.doi.org/10.4236/fns.2016.711099
Received:
August 20, 2016
Accepted:
September 20, 2016
Published:
September 23, 2016
Copyright © 201
6 by authors and
Scientific
Research Publishing Inc.
This work is licensed under the Creative
Commons Attribution International
License (CC BY
4.0).
http://creativecommons.org/licen
ses/by/4.0/
Open Access

E. N. Fombang, R. W. Saa
1022
1. Introduction
Diabetes is a metabolic disorder characterized by a dysfunction of carbohydrate meta-
bolism resulting in hyperglycemia [1]. Worldwide, 415 million people were estimated
to have diabetes in 2015, with this number projected to increase to 642 million in 2040
[2]. These figures translate in one in eleven adults having diabetes. Three quarters of
these persons live in low and middle income countries, and diabetes was responsible for
five million deaths in 2015 alone [2]. Maintenance of glucose homeostasis is of utmost
importance to human physiology. Failure to maintain this control can result in meta-
bolic syndrome, a multi symptom disorder of energy homeostasis encompassing obesi-
ty, hyperglycemia, impaired glucose tolerance, hypertension and dyslipidemia [3]. In-
sulin resistance is the most characteristic abnormality present in metabolic syndrome.
It results from interactions between genetic and environmental factors, including diet
and a sedentary lifestyle [3]. Metabolic syndrome is the major predisposing factor for
type 2 diabetes, where defects in both insulin action and insulin secretion are present.
Among the multiple risk factors associated with the incidence and progression of
type 2 diabetes, diet is the main modifiable factor. As reviewed by Bahadoran
et al
. [4],
several epidemiological investigations have shown that diets rich in foods with high
content of phytochemicals and high antioxidant capacity may be related to lower risk of
diabetes and its predisposing factors. Dietary plant polyphenols and polyphenol-rich
products modulate carbohydrate and lipid metabolism, attenuate hyperglycemia, dysli-
pidemia and insulin resistance [3] [5] [6]. In addition, polyphenols are safe and present
no side-effects. Recently the use of functional foods and their bioactive components
have been considered as a new approach in the prevention and management of diabetes
and its complications [4]. Polyphenols, due to their biological properties, may be ap-
propriate nutraceuticals and supplementary treatments for diabetes mellitus.
Moringa oleifera
is a plant used in the management of type 2 diabetes and belongs to
the Moringaceae family. Water and ethanol extracts of its leaves have been shown to
possess hypoglycemic, antihyperglycemic and antidiabetic activity in normoglycemic
and in diabetic rats [5]-[8]. These have mostly been used in the powder form and with
animal models. Its anti-diabetic activity may be attributed to phenolic compounds such
as flavonoids, phenolic acids, and tannins which have been reported to have antihyper-
glycemic activity [3] [9] [10]. Previously, optimal conditions for the production of a
phytochemical-rich, antioxidant
Moringa oleifera
leaf functional tea were determined
[11]. This tea is rich in polyphenols, has antioxidant and reducing capacity similar to
DPPH and ascorbic acid respectively. With the recent interest in functional foods for
the control of blood glucose, the present study investigates the potential of this tea in
regulating blood glucose levels in human subjects and in rat models.
2. Materials and Methods
2.1. Plant Material and Preparation of Flour
Moringa oleifera
leaves were harvested in Maroua in the Far North Region of Came-
roon and transported to the Food Biophysics, Biochemistry and Nutrition Laboratory,

E. N. Fombang, R. W. Saa
1023
of the National School of Agro-Industrial Sciences (ENSAI) of the University of
Ngaoundere. Leaflets were detached from the
Moringa oleifera
leaves, sorted to remove
dead leaves, washed with distilled water, rinsed and drained on plastic trays for 30 mi-
nutes before drying at 45˚C ± 2˚C for 14 h in a ventilated electric dryer (Riviera & Bar
QD105A, Paris, France). Dried leaves were ground in a mill (Culatti, Polymix, France)
and sieved through a 500 μm sieve to obtain powder. The powder samples were stored
in airtight glass jars at 4˚C.
2.2. Preparation of Moringa oleifera Functional Tea
Using previously established optimal conditions [11],
Moringa oleifera
functional tea
was prepared by extracting Moringa leaf powder in distilled water at a ratio of 1:20
g/ml, at 97˚C for 35 min, and filtered using Whatman filter paper.
2.3. Characterization of M. oleifera Functional Tea
2.3.1. Determination of Phytochemical Content
1) Total polyphenols
The total polyphenols were determined by the method of [12]. Extract (10 μl) was
diluted 20 times with distilled water (2.99 ml) in a test tube and mixed with 500 μl of
Folin-Ciocalteu reagent and 400 μl of 7.5% sodium carbonate (w/v). The mixture was
votexed, and incubated in the dark at room temperature for ten minutes. The absor-
bance was measured at 760 nm using a spectrophotometer (Metertech SP8001, Germa-
ny). Total phenolic content was calculated against a calibration curve established using
gallic acid and expressed as mg gallic acid equivalent (GAE) per 100 ml.
2) Total flavonoids
Total flavonoids were determined by a colorimetric method as described by [13]. To
0.1 ml of extract was added 2.4 ml of distilled water and 0.15 ml of sodium nitrite (5%
w/v) and the mixture incubated at 25˚C for 5 mins. Thereafter, 0.15 ml of Aluminum
chloride hexahydrate (10% w/v) was added followed by a second incubation. Finally 1
ml of 1M sodium hydroxide solution was added and the optical density was read at 510
nm against a reagent blank. A calibration curve was established using catechin solution.
Flavonoid concentration was calculated from the calibration curve and expressed as ca-
techin equivalents per 100 ml.
3) Total tannins
Total tannins were determined using the vanillin HCl method [14]. To 1 ml of ex-
tract was added 3 ml of 4% (w/v) vanillin in methanol, followed by addition of 1.5 ml
concentrated hydrochloric acid. The mixture was vortexed and incubated at 30˚C for 20
min. The absorbance was read at 500 nm against a blank. Tannin content was calcu-
lated from a standard curve prepared using tannic acid solution (0.2 g/L). The results
were expressed as equivalent grams of tannic acid per 100 ml.
2.3.2. Determination of Antioxidant Activity
1) DPPH radical scavenging activity
Antioxidant capacity (Radical scavenging activity) of
M. oleifera
functional tea was

E. N. Fombang, R. W. Saa
1024
determined using the modified Brand-Williams
et al.
[15] method. DPPH (2,2’-di-
phenyl-1-picryl hydrazyl) in ethanol is a stable radical, dark violet in color. Its color is
bleached by its reaction with a hydrogen donor. For analyses, 0.1 ml of
M. oleifera
tea
was added to 2 ml of 100 μM DPPH solution in ethanol. Ethanol without extract was
included as control. The reaction mixture was incubated for 30 min in the dark at 25˚C
and the absorbance read at 517 nm. Vitamin C was used as the standard against which
the antioxidant activity of the tea was compared. The free radical scavenging activity
was calculated as follows:
( ) ( )
Abs.control Abs.extract 100
DPPH Radical Scavenging Activity % Abs.control
−∗
=
where Abs. is the Absorbance at 517 nm.
DPPH activity was expressed as % inhibition.
2) Total reducing power
The reducing power of
M. oleifera
functional tea was determined by the method of
[16] using potassium ferricyanide (K3Fe(CN)6). An aliquot of extract (100 μl) was
mixed with equal amounts of 0.2 M phosphate buffer (pH 6.6) and 1% potassium ferri-
cyanide and incubated for 20 min at 50˚C followed by precipitation with 10% TCA. Af-
ter centrifugation at 3500 rpm for 15 minutes, the supernatant was diluted with equal
volumes of distilled water and 100 μl of 0.1% ferric chloride (FeCl3) to determine ferric
reducing capacity of Moringa tea. The absorbance was read at 700 nm against a reagent
blank. A higher absorbance indicates a higher reducing power because more ferric cya-
nide is reduced to ferrous cyanide by the tea. Ascorbic acid was used as reference stan-
dard and results expressed as ascorbic acid equivalence (g AAE/100g Dry Matter DM).
3) Ferrous ion chelating power
Ferrous ion chelating power was determined using the method of Suter and Richter
[17] with slight modification. Reagent solution (100 µl of ferrous chloride (2 mM) +
400 µl of potassium ferro cyanide 5 mM) was mixed with 200 µl of Moringa tea and 1
mL of distilled water. The mixture was incubated at 20˚C for 10 min and the absor-
bance read at 700 nm using a spectrophotometer (Metertech SP8001, Germany). EDTA
standard was used as a positive control. Ferrous ion chelating power CP was calculated
using the formula:
( )
control tea
control
% 100.
AA
CP A
−
= ×
2.4. Antihyperglycemic Activity of Moringa oleifera Functional Tea
The antihyperglycemic activity of
Moringa oleifera
functional tea was determined in rat
models and in human subjects using the oral glucose tolerance test (OGTT). The ability
of Moringa tea to complex free glucose in solution was also determined.
2.4.1. Antihyperglycemic Activity in Rat Models
Twenty five male Wistar albino rats, weighing between 250 and 378 g were obtained
from the animal laboratory of the Faculty of Science of the University of Ngaoundere.

E. N. Fombang, R. W. Saa
1025
The animals were housed individually in semi-metabolic cages in the animal house of
the National School of Agro-industrial Sciences (ENSAI), at an average temperature of
25˚C ± 2˚C and a relative humidity of 60% - 70% with 12/12 h cycles of light and dark-
ness. Rats were allowed to acclimatize for one week on a standard rat diet. The animals
had free access to food and water during this period.
At the end of the acclimatization period, the rats were randomly assigned into 5
groups of 5 animals each for the antihyperglycemic experiments. The groups comprised
a negative (G1) and a positive (G2) control group, with 3 experimental (G3, G4, G5)
groups. To determine the antihyperglycemic activity of
Moringa oleifera
functional tea,
rats were fasted overnight for 12 h. After the overnight fast, blood was withdrawn from
the animal’s tail vein and fasting blood glucose measured using a glucometer (One-
Touch Ultra 2, LifeScan, Inc.) [18]. Thereafter, animals in the control groups (G1, G2)
were gavaged with distilled water at doses of 20 ml/kg body weight (BW), while animals
in the 3 treatment groups (G3, G4, G5) were gavaged with Moringa tea at doses of 10,
20 and 30 ml/kg BW respectively. Thirty minutes later, glucose overload was given to
the animals in the positive control group G2 and the 3 treatment group by gavage at a
dose of 4 g/kg BW. The negative control group G1 was given distilled water. Blood
glucose level was measured at intervals of 30 min for the next 150 min following glu-
cose administration. Animals were treated in accordance with the guidelines for animal
experimentation of the University of Ngaoundere [19].
2.4.2. Antihyperglycemic Activity in Human Subjects
To determine antihyperglycemic activity of Moringa tea in humans, the effect of a sin-
gle ingestion of Moringa tea on postprandial blood glucose elevation in normal subjects
was evaluated. Fifteen normoglycemic male volunteers aged 20 to 29 years, all student
of the University of Ngaoundere, participated in the study. The students weighed be-
tween 60 and 80 kg, with height ranging from 1.72 to 1.83 m, and an average BMI of
21.6 ± 1.7 Kg/m2. Fasting blood glucose of the subjects taken twice and for 2 days con-
secutively ranged between 70 and 98 mg/dl with a mean of 86.2 ± 8.4 mg/dl. The sub-
jects were thus non-diabetic as their fasting blood glucose level was below the patho-
logical level of >126 mg/dl [1]. Prior to taking part in the study, its purpose was ex-
plained to the participants and their informed consent obtained. The study protocol
was approved by the ethics committee of the University of Ngaoundere.
The fifteen volunteers were randomly assigned into 3 groups of five persons each.
The 3 groups consisted of a control group and 2 treatment groups. All the subjects were
fasted overnight for 12 h, after which their blood glucose level was measured in blood
obtained by the finger-prick method using a glucometer (OneTouch Ultra 2, LifeScan,
Inc.). The subjects were then given 200 ml (1 cup) and 400 ml (2 cups) of Moringa tea
for the treatment groups T1 and T2 respectively, while the control group received 200
ml distilled water. The tea and water was consumed within 5 min. This was followed 30
min later by the administration of 50 g of glucose (Munro Glucose-D) in 200 ml of dis-
tilled water, for all the three groups. Blood glucose was then measured at intervals of 30
min for the next 150 min. Duplicate measurements were taken per subject.

E. N. Fombang, R. W. Saa
1026
2.5. Complexation of Glucose by Moringa Tea
This test estimates the capacity of Moringa tea to complex free glucose
in vitro
. For this,
10 ml of a glucose solution (0.61 g/l) was mixed with 10 ml of Moringa tea. For the
control sample, 10 ml of glucose solution was mixed with 10 ml of distilled water. The
resulting mixture was incubated at 37˚C for 15 min [18]. Unbound glucose remaining
in solution after this time was measured using the method of [19].
2.6. Expression of Results and Statistical Analysis
Percentage reduction in blood sugar was calculated as the difference in blood glucose at
time
t
between the treatment group and the control group. Total reduction in blood
glucose was calculated as proposed by [20].
Results are presented as means ± SD, and means were separated using the Duncan
Multiple Range Test at the 5% level with the software Stat-graphic centurion 15.2
(StatPoint Technologies, Inc, Warrenton, Virginia, USA). Graphs of changes in blood
glucose level with time were plotted using Sigma Plot version 11.
3. Results
3.1. Phytochemical Content and Antioxidant Capacity of M. oleifera
Functional Tea
Phenolic compounds content and antioxidant capacity of
M. oleifera
functional tea are
presented on Table 1. Moringa tea contains respectively 56.96, 34.66 and 3.53 mg/100
ml of total polyphenols, flavonoids and tannins. It equally possesses significant anti-
oxidant capacity with radical scavenging activity (81%), a chelating power of 85% and
total reducing power of 1.75 g Ascorbic Acid Equivalent/100g DM.
3.2. Test of Glycosylation or Glucose Complexing
The glycosylation test gives the amount of glucose complexed by the tea and thus un-
available for digestion and or absorption. Addition of
M. oleifera
tea to glucose solution
reduced the amount of glucose detectable in solution by 36.57%.
Table 1. Phytochemical contents and antioxidant capacity of
M. oleifera
functional tea.
Component Quantities
Phytochemical content
Total polyphenols (mg/100ml) 56.96 ± 0.75
Total flavonoids (mg/100ml) 34.66 ± 0.72
Total tannins (mg/100ml) 3.53 ± 0.03
Antioxidant capacity
DPPH scavenging activity (% inhibition) 80.94% ± 0.76%
Chelating power (% inhibition) 85.26% ± 10.9%
Total reducing power (g AAE/100g DM) 1.75 ± 0.21
AAE: Ascorbic acid equivalence.

E. N. Fombang, R. W. Saa
1027
3.3. Antihyperglycemic Effect of M. oleifera Functional Tea on Blood
Glucose in Rat Models
The effect of different doses of
M. oleifera
tea on blood glucose levels in rats is shown in
Figure 1 and Table 2. All the animals had similar fasting blood glucose, but that of the
negative control group (G1) that received only distilled water remained stable (64.0 ±
4.5 mg/dl) throughout the experimental period. Glucose ingestion resulted in an in-
crease in blood glucose levels. Consumption of Moringa tea prior to glucose overload
did not bring about any significant reduction in blood glucose levels for up to 60 min in
group G4 and up to 90 min in groups G3 and G5. Beyond these times, blood glucose
dropped significantly (p < 0.05) in the treatment groups compared to G2 (Figure 1).
Time (min)
020 40 60 80 100 120 140 160
Blood Glucose (mg/dl)
20
40
60
80
100
120
140
160
G1: Distilled water
G2: Distilled water +glucose
G3: Moringa tea (10 ml)+glucose
G4: Moringa tea (20 ml)+glucose
G5: Moringa tea (30 ml)+glucose
Figure 1. Effects of
Moringa oleifera
tea on blood glucose level of experimental rats. Tea (ml/kg
BW); glucose (4 g/kg BW).
Table 2. Percentage reduction of glycaemia at different doses of administration of
Moringa olei-
fera
tea in rats.
Groups
Percentage (%) reduction in glycaemia % total
30 min 60 min 90 min 120 min 150 min Reduction
G3: 10 ml/Kg BW 1.89 4.78 6.78 29.30 34.71 13.25
G4: 20 ml/Kg BW 8.71 4.32 34.67 28.42 35.12 18.21
G5: 30 ml/Kg BW 2.65 2.99 6.91 12.97 11.98 6.01
G3: Moringa tea (10 ml/kg BW) + glucose 4 g/kg BW; G4: Moringa tea (20 ml/kg BW) + glucose 4 g/kg BW; G5:
Moringa tea (30 ml/kg BW) + glucose 4 g/kg BW.

E. N. Fombang, R. W. Saa
1028
Although G3 had a latent antihyperglycemic effect (after 90 min) compared to G4 (after
60 min), final glucose levels in both groups were comparable at 120 min (91.7 and 92.7
mg/dl respectively) and at 150 min (79 and 78.5 mg/dl respectively). Group G5 had
higher glucose levels at 120 (112.7 mg/dl) and 150 (106.5 mg/dl) min in comparison. At
150 min, Moringa tea suppressed glucose elevation by 34.71%, 35.12% and 11.98% re-
spectively at doses of 10 (G3), 20 (G4) and 30 (G5) ml/kg BW (Table 2). Lower doses
were thus more effective in preventing hyperglycemia.
3.4. Antihyperglycemic Effects of M. oleifera Funtional Tea on Blood
Sugar Levels of Normal Human Subjects
In humans, consumption of glucose alone (control group) significantly raised blood
glucose levels which peaked after 30 min and thereafter decreased steadily down to 109
mg/dl at 150 min (Figure 2). The consumption of Moringa tea before glucose adminis-
tration, irrespective of dose attenuated the rise in postprandial blood glucose observed
in the control group. However, the behavior of postprandial glucose with time was dose
dependent. Lower dose of Moringa tea 200 ml (T1) was more effective (22.8%) in pre-
venting the rise in blood glucose than higher dose (17.9%) 400 ml (T2), 30 min follow-
ing glucose overload (Figure 2 and Table 3). Beyond this time, blood glucose of sub-
jects in group T1 remained constant up to 90 min before dropping down to 88.3 ± 8.0
mg/dl at 120 min. After the initial rise in blood glucose at 30 min with a higher dose of
tea (T2), there was a linear drop in glucose level down to 91.5 ± 6.6 mg/dl at 120 min
(Figure 2). In spite of their different trends, final blood glucose concentration at 150
min was comparable in both treatment groups (88.5 and 84 mg/dl respectively for
groups T1 and T2), and was significantly (p < 0.05) lower that of the control group
(109.3 mg/dl).
Figure 2. Effect of
Moringa oleifera
tea on blood glucose level of human subjects.

E. N. Fombang, R. W. Saa
1029
Table 3. Percentage reduction in glycaemia at different doses of administration of
Moringa olei-
fera
tea in humans.
Groups
Percentage (%) reduction in glycaemia % total
30 min 60 min 90 min 120 min 150 min Reduction
T1: 200 ml tea 22.79 22.15 10.60 20.45 19.03 16.93
T2: 400 ml tea 17.93 20.38 29.95 17.57 23.15 19.05
T1: 200 ml Moringa tea + 50 g glucose; T2: 400 ml Moringa tea + 50 g glucose.
4. Discussion
Phenolic compounds are bioactive compounds with antioxidant potential, hypogly-
cemic, hypolipidemic and anti-tumor properties [21] [22].
Moringa oleifera
functional
tea contains polyphenols, flavonoids and tannins, making it a source of phenolic com-
pounds. Dietary intake of polyphenols is estimated at 1g per day [4]. Therefore a cup of
Moringa tea (200 ml), with 111.2 mg polyphenols supplies one tenth of daily needs,
whereas two cups (400 ml) will supply one fifth of daily requirements.
In this study we demonstrate the antihyperglycmic activity of
Moringa oleifera
func-
tional tea in rat models and in human subjects. In rat models the antihyperglycemic ef-
fect was more pronounced 90 min after glucose loading and more so at doses of 20
ml/kg BW which impaired blood glucose rise by 34.67% vs 6.78% and 6.91% for low G3
(10 ml/kg BW) and high G5 (30 ml/kg BW) doses respectively. As evident from final
blood glucose levels at the end of the experiment (Figure 1, Table 2), high dose G5 was
least effective in reducing glycemia. The reason for this is not clear. However, the fact
that increase in glycemia was not substantially reduced 60 min after the administration
of glucose, may point to the fact that the mechanisms for glucose control intervene
more at the level of circulation than at intestinal level. Recent work by [6] showed that
normal and diabetic rats feed low and high doses (200 and 400 mg/kg/BW/day) of
powders from
Moringa oleifera
leaf aqueous extracts for 30 days, showed better gly-
cemic control and an improvement in pancreatic cell and in insulin production espe-
cially in diabetic rats. Previous work by [8] reported better glucose tolerance (25.99%,
31.25% and 43.19%) in normal mice fed powders of Moringa leaf aqueous extracts at
doses of 100, 200 and 300 mg/100g BW). These results agree with ours; but their anti-
hyperglycemic effect is achieved with higher doses compared to our study. This sug-
gests that Moringa tea maybe a better and convenient form of consumption of Moringa
for more efficient glycemic control.
In humans on the other hand, the antihyperglycemic effect was rapid, decreasing
blood glucose by 22.8% and 17.9%, 30 min after glucose loading with doses of 200 and
400 ml respectively. Although a high dose of Moringa tea was less effective initially in
preventing the rise in blood glucose, it achieved a greater reduction in glucose levels at
90 min compared to low dose T1. The greater reduction observed at 30 min with low
doses of tea T1, coupled with the stable glucose levels up to 90 min (Figure 1), suggests
that the effect of this dose was more important at the intestinal level possibly through
inhibition of glucose uptake. Our results of 36.57% reduction in free glucose in solution

E. N. Fombang, R. W. Saa
1030
following incubation with Moringa tea supports this assertion, as it would appear that
Moringa tea binds glucose. Higher doses appear to exhibit their antihyperglycemic ac-
tivity more in circulation than at the intestinal level considering their slower effect in
preventing blood glucose increase at 30 min and the rapid drop in blood glucose the-
reafter.
Aqueous and methanolic extracts of
Moringa oleifera
have previously been shown to
possess antihyperglycemic and antidiabetic activity, which has been attributed to their
polyphenols content particularly phenolic acids, flavonoids and tannins [5]-[8]. We
show in this study that Moringa functional tea equally possesses these benefits and is a
more convenient form of consumption of polyphenols from
Moringa oleifera
. Possible
antihyperglycemic mechanisms for polyphenols include inhibition of
α
-amylase,
α
-
glucosidase and intestinal glucose absorption by sodium-dependent glucose transpor-
ters at intestinal level [3] [22]-[25]; improving glucose uptake by peripheral tissues,
suppression of gluconeogenesis and stimulation of insulin secretion in circulation [3]
[23] [26]. The differences in blood glucose changes observed with high and low doses in
humans and rat models may indicate that different mechanisms are at work and needs
further investigations.
Moringa tea exhibited strong antioxidant potential which may be working in synergy
with glucose inhibition by polyphenols to booster its antihyperglycemic effect. Signifi-
cant increases in insulin secretion and decrease in blood glucose following glucose
loading have been reported in rats previously fed high antioxidant
α
-tocopherol diets
compared to rats whose diet was deficient in
α
-tocopherol [27]. The authors suggested
that
α
-tocopherol reduced oxidative stress and thus increased insulin secretion which
led to a reduction in blood glucose.
5. Conclusion
Tea being a widely consumed beverage, this study demonstrates that
Moringa oleifera
functional tea has antihyperglycemic activity in rat models and in human subjects, and
may be a convenient form for the consumption of Moringa polyphenols. In addition,
Moringa tea has strong antioxidant potential which may boost its antihyperglycemic
effect.
Moringa oleifera
tea could thus be beneficial as a functional food in regulating
blood glucose levels and preventing further complications of diabetes. Further studies
are needed to evaluate its effect in diabetic conditions and to better understand its
mode of action.
Acknowledgements
The authors express their gratitude to all the students who participated voluntarily in
the study.
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