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Effect of Avocado Leaf Extract on the Decrease of Fasting Blood Glucose Level of White Rats

Authors:
OPEN ACCESS Asian Journal of Scientific Research
ISSN 1992-1454
DOI: 10.3923/ajsr.2019.287.292
Research Article
Effect of Avocado Leaf Extract on the Decrease of Fasting Blood
Glucose Level of White Rats
1Nurdin Rahman, 2Sri Mulyani Sabang, 1Nikmah Utami Dewi and 1Bohari
1Department of Nutrition, Faculty of Public Health, Tadulako University, Indonesia
2Chemical Education Study Program, Faculty of Teacher Training and Education Sciences, Tadulako University, Indonesia
Abstract
Background and Objective: Preclinical testing of the use of avocado leaf extract for decreasing blood glucose level is still limited. This
study aimed to analyze the effect of avocado leaf extract on fasting blood glucose level in male white rats. Materials and Methods: This
study was a pre-experiment with six groups of pretest posttest with control group. The samples were male white rats (
Rattus norvegicus
)
of Wistar strain, ±3 months old, with the treatment groups: Group 1: Feed+Streptozotocin (STZ)+10% sucrose+avocado leaf extract dose
of 100 mg kgG1 b.wt., Group 2: Feed+STZ+10% sucrose+avocado leaf extract dose 150 mg kgG1 b.wt., Group 3: Feed+STZ+10%
sucrose+avocado leaf extract dose 200 mg kgG1 b.wt., Group 4: Feed+STZ+10% sucrose, Group 5: Feed+STZ+10% sucrose+glibenclamide
and Group 6: Feed. Data analysis used ANOVA and paired t-test with p<0.05. Results: The early fasting blood glucose level of the white
rats was 58-97 mg dLG1 (p = 0.897). Giving STZ increases the fasting blood glucose level to 83-128 mg dLG1 (p = 0.136). Meanwhile, giving
avocado leaf extract on day 14 decreased 68-77 mg dLG1 (p = 0.000). Group 2 experienced a significant decrease on day 7, which was
28.22 mg dLG1 (p = 0.028) and day 14, which was 31.33 mg dLG1 (p = 0.015). Conclusion: Avocado leaf extract with a dose of
150 mg kgG1 b.wt. is effective in reducing the high fasting blood glucose level in white rats.
Key words: Avocado leaf extract, fasting blood glucose, white rats, streptozotocin, glibenclamide
Received: October 10, 2018 Accepted: November 16, 2018 Published: March 15, 2019
Citation: Nurdin Rahman, Sri Mulyani Sabang, Nikmah Utami Dewi and Bohari, 2019. Effect of avocado leaf extract on the decrease of fasting blood glucose
level of white rats. Asian J. Sci. Res., 12: 287-292.
Corresponding Author: Bohari, Department of Nutrition, Faculty of Public Health, Tadulako University, Central Sulawesi, Palu, Indonesia
Tel:+6285253587076
Copyright: © 2019 Nurdin Rahman
et al
. This is an open access article distributed under the terms of the creative commons attribution License, which
permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.
Competing Interest: The authors have declared that no competing interest exists.
Data Availability: All relevant data are within the paper and its supporting information files.
Asian J. Sci. Res., 12 (2): 287-292, 2019
INTRODUCTION
Uncontrolled glucose level is the main problem
experienced by patients with Type 2 Diabetes Mellitus (T2DM)
which can cause complications such as heart disease,
hypertension, stroke, kidney failure, blindness, cancer and
impotence1,2. People generally use certain parts of plants to
reduce high blood pressure, blood glucose level and
cholesterol. The use of plant parts raises questions related to
the quality, efficacy and safety3. Therefore, it needs to be
empirically investigated. Most natural anti-oxidants come from
fruits, vegetables, spices and grains such as ginseng, curcuma,
rosemary, green tea, grapes, ginger, garlic and avocado4-7.
Previous studies showed that plant leaf extract could
reduce blood glucose level in white rats, such as
Sintowati
et al
.8 that used 70% methanol extract of avocado
leaves (
Persea americana
Mill) with a dose of 200 mg/200,
100 mg/200 and 150 mg/200 g/body weight which can
reduce blood glucose level in male Wistar white rats.
Furthermore, Putri
et al
.6 found that avocado leaf extract is
able to decrease the level of glucose and the most effective
concentrate is 10%. Hariantos research on the effect of
n-butanol fraction of avocado leaves (
Persea americana
Mill)
extract on male white rats showed that it can reduce blood
glucose level effectively at a dose9 of 1.0 g kgG1 b.wt.
Other studies showed that avocado leaf extract using
ethanol solution displays a strong antioxidant activity against
DPPH (1,1-diphenyl-2-picrylhydrazyl) and that the effects of
phytochemical combinations (flavonoids, saponins, tannins
and steroids) from avocado leaf extract can be used in the
treatment of oxidative stress10.
Based on the previous research, this study was
conducted by using different dose variants and avocado leaf
extract by using ethanol solution to produce avocado leaf
extract products that are useful for lowering blood glucose
level. Preclinical testing of avocado leaf extract is needed to
assess the ability of avocado leaves in reducing blood glucose
level. Therefore, this study aimed to analyze the effect of
avocado leaf extract on fasting blood glucose level in male
white rats.
MATERIALS AND METHODS
Research type: This study was a pre-experiment with six
groups of pre-test and post-test with control group. This
research was carried out in the Pharmacology Laboratory of
Pelita Mas Palu STIFA for 5 months in 2018.
Preparation of test animals: Eighteen male Wistar strain
white rats were adapted for 2 weeks in a laboratory with
adequate cages at normal ambient temperatures and given
standard feed and drinking. The type of standard feed was
Turbo Feed with a protein of 16-18%, fat 4%, ash content 12%,
fiber 8% and moisture content 12%.
Tools: Glucose measuring devices (Accu Check Active),
Aluminum Foil, Stirring Rods, Blenders (Panasonic), Porcelain
Cups, Funnels, 1000 mL Chemical Glasses (Agc Iwaki Cte 33),
100 mL Measuring Cups (Pyrex), Test Animal Enclosures,
Measuring Flasks 100 Ml, Mortar and Stamper, Pipette Drops,
Rotary Evaporator (Heidolph), Oral Sonde, Injection Spoit
(Treumo) 3 and 5 mL, Glucose Strips, Reaction Tubes,
Analytical Scales (Ohaus), Gram Scales, Water bath and
Maceration Containers.
Avocado leaf extract: Avocado leaves were extracted with
70% of positive ethanol solution containing flavonoid
compounds, saponins, tannins, steroids. The 70%
concentration is an avocado leaf extract that gives absorbance
value and optimum percent inhibition10.
Testing of antidiabetic effects: On da y 0 a fte r ad ap tat ion ,
the rats were fasted for 16 h. Then, the initial fasting blood
glucose level was measured. After the initial blood glucose
level was measured, on the same day, streptozotocin (STZ)
rats were induced with 30 mg kgG1 b.wt., intraperitoneally.
On the 3rd day after the induction, the rats were fasted
for 16 h. Then, the blood glucose level of the rats was
measured. After the fasting blood glucose level of the rats had
reached a state of hyperglycemia, they were given the oral
treatment for 7 days. The treatment was c ontin ued u p to
14 days.
Treatment groups:
Group 1 : Feed+STZ+10% sucrose+avocado leaf extract dose
of 100 g kgG1 b.wt.
Group 2 : Feed+STZ+10% sucrose+avocado leaf extract dose
of 150 g kgG1 b.wt.
Group 3 : Feed+STZ+10% sucrose+avocado leaf extract dose
200 g kgG1 b.wt.
Group 4 : 10% feed+STZ+sucrose
Group 5 : Feed+STZ+10% sucrose+glibenclamide
Group 6 : Feed
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Asian J. Sci. Res., 12 (2): 287-292, 2019
Time for measurement of body weight and fasting blood
glucose level:
Measurement 1 : Before STZ induction
Measurement 2 : After STZ induction
Measurement 3 : 7 days after the intervention of avocado
leaf extract
Measurement 4 : 14 days after the intervention of avocado
leaf extract
Research ethics: This study has obtained an ethical
recommendation agreement Number: 546/H4.8.4.31/PP36-
KOMETIK/2018 issued by the Health Research Ethics
Committee of the Faculty of Medicine RSPTN Hasanuddin
University, RSUP Dr. Wahidin Sudirohusodo Makassar.
Data analysis: Da t a a n al y si s wa s co n du c te d by u si n g o n e- w ay
ANOVA test and paired t-test with a significance level of 5% or
p<0.05.
RESULTS
As Table 1 showed the white rats were grouped into
6 groups at the be ginn ing of the st udy w ith 1 8 whi te ra ts
not having a significantly different body weight with
p-value = 0.090 (p>0.05). The body weight of the white rats
ranged from 133-225 g. Before the intervention of avocado
leaf extract was done, an attempt to increase the fasting blood
glucose level was done by giving STZ to the white rats. ANOVA
test results showed that there were no significant differences
in body weight among the 6 groups after the rats were given
STZ with p = 0.095 (p>0.05).
On the 7th day after the rats were given avocado leaf
extract, the body weight showed a significant difference
between the 6 groups with p = 0.016 (p<0.05). Rats in groups
3, 5 and 6 had the heaviest body weight of 239.33 g
(groups 3), 240.00 g (groups 5), 249,67 g (groups 6) (Table 1).
Measurement IV is 14 days after the intervention of avocado
leaf extract necessary to find out the effective time of avocado
leaf extract on weight and fasting blood glucose of mice.
As Table 2 showed the fasting blood glucose level of
white rats grouped into 6 groups was not different with
p = 0.897 (p>0.05) and the fasting blood glucose level of the
white rats ranged from 58-97 mg dLG1. The giving of STZ at the
second measurement also showed that there were no
significant differences in fasting blood glucose level between
the 6 groups with p = 0.136 (p>0.05) and fasting blood
glucose level of the white rats ranged from 83-128 mg dLG1.
The fasting blood glucose level of the white rats on day 14
after the rats had been given the avocado leaf extract showed
a significant difference between 6 groups with p = 0.000
(p <0.05). Group 2 had the lowest fasting blood glucose level
of 73.33±4.72 mg dLG1 and group 4 had the highest fasting
blood glucose level of 104.00±10.81 mg dLG1 (Table 2).
Table 1: White rats body weight during research
Body weight (g)
Measurement Treatment ----------------------------------------------------------
time groups n Mean±SD Min-max p-value (one-way ANOVA test)
I Group 1 3 151.67±16.28 133-163 0.090
Group 2 3 202.67±28.92 170-225
Group 3 3 185.67±17.21 166-198
Group 4 3 187.67±32.32 152-215
Group 5 3 209.33±9.02 200-218
Group 6 3 210.33±31.34 182-244
II Group 1 3 158.00±22.11 133-175 0.095
Group 2 3 208.67±26.50 179-230
Group 3 3 199.67±11.02 189-211
Group 4 3 189.33±29.28 158-216
Group 5 3 210.00±13.00 202-225
Group 6 3 214.00±29.54 190-247
III Group 1 3 178.00±20.95 155-196 0.016
Group 2 3 213.33±23.24 187-231
Group 3 3 239.33±10.21 232-251
Group 4 3 195.67±24.13 169-216
Group 5 3 240.00±15.58 231-258
Group 6 3 249.67±36.67 221-291
IV Group 1 3 194.33±17.15 176-210 0.078
Group 2 3 224.67±19.29 203-240
Group 3 3 232.67±10.97 220-239
Group 4 3 214.33±19.14 193-230
Group 5 3 247.00±11.35 239-260
Group 6 3 246.67±38.83 215-290
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Asian J. Sci. Res., 12 (2): 287-292, 2019
Table 2: White rats fasting blood glucose level during research
Fasting blood glucose level (mg dLG1)
Measurement Treatment ----------------------------------------------------------
time groups n Mean±SD Min-max p-value (one-way ANOVA test)
I Group 1 3 82.00±8.88 72-89 0.897
Group 2 3 73.00±13.22 58-83
Group 3 3 78.00±6.08 71-82
Group 4 3 77.67±5.85 71-82
Group 5 3 72.00±12.00 60-84
Group 6 3 78.67±18.50 60-97
II Group 1 3 114.67±13.01 102-128 0.136
Group 2 3 104.67±2.08 103-107
Group 3 3 98.00±14.52 83-112
Group 4 3 93.67±8.96 88-104
Group 5 3 104.67±2.30 102-106
Group 6 3 97.00±4.35 92-100
III Group 1 3 90.67±8.50 81-97 0.321
Group 2 3 76.33±6.42 69-81
Group 3 3 169.00±111.90 98-298
Group 4 3 93.67±18.14 77-113
Group 5 3 129.67±57.81 90-196
Group 6 3 91.67±4.04 87-94
IV Group 1 3 93.67±5.68 89-100 0.000
Group 2 3 73.33±4.72 68-77
Group 3 3 76.00±5.29 70-80
Group 4 3 104.00±10.81 95-116
Group 5 3 91.33±2.08 89-93
Group 6 3 82.33±1.15 81-83
Table 3: Fasting blood glucose (FBG) level after giving avocado leaf extract test
Treatment groups n ) FBG(I) vs. FBG(II) p-value ) FBG(II) vs. FBG(III) p-value ) FBG(II) vs. FBG(IV) p-value
Group 1 3 32.66 0.111 24.00 0.096 21.00 0.147
Group 2 3 31.66 0.048 28.22 0.028 31.33 0.015
Group 3 3 20.00 0.063 71.00 0.342 22.00 0.190
Group 4 3 16.00 0.201 0.00 NA 10.33 0.042
Group 5 3 32.66 0.044 25.00 0.546 13.33 0.022
Group 6 3 18.33 0.172 5.33 0.004 14.66 0.036
Paired t-test, FBG(I): Fasting blood glucose before STZ induction, FBG(II): Fasting blood glucose after STZ induction, FBG(III): Fasting blood glucose 7 days after the
intervention of avocado leaf extract, FBG(IV): Fasting blood glucose 14 days after the intervention of avocado leaf extract, NA: Not acceptable, ): Delta
Table 3 showed that there were significant differences in
fasting blood glucose level after the rats in group 2
(difference of 31.66 mg dLG1, p = 0.048) and group 5
(difference of 32.66 mg dLG1, p = 0.044) were given STZ. This
showed that fasting blood glucose for group 2 and 5 increased
after STZ induction. The difference in fasting blood glucose
level after giving avocado leaf extract for 7 days showed that
group 2 and group 6 experienced a significant decrease with
p<0.05.
The significant difference in fasting blood glucose level
after the giving of avocado leaf extract for 14 days showed
that groups 2, 5 and 6 experienced a significant decrease with
p<0.05, while group 4 experienced a significant increase with
p = 0.042.
DISCUSSION
The results showed that avocado leaf extract had a
significant effect in reducing fasting blood glucose level in
white rats at a dose of 150 g kgG1 b.wt. The dose of 100 and
200 g kgG1 b.wt., did not show a positive change in fasting
blood glucose level in white rats. This indicated that the dose
of avocado leaf extract that is too low and high does not have
a positive effect on decreasing fasting blood glucose level.
The white rats used in this study had normal fasting blood
glucose level as shown in the first measurement in Table 2.
Furthermore, Streptozotocin (STZ) injection was done in group
1-6 aimed to increase fasting blood glucose level in white rats.
This is because STZ injected intraperitoneally acts as
diabetogenic which will enter pancreatic $ cells through
the glucose transporter (GLUT-2)11. This study also used
glibenclamide in group 5 as a positive control. This was used
as a comparison of the effects of avocado leaf extract with
various doses12. This study showed that a dose of 150 mg dLG1
equals the ability of glibenclamide to reduce fasting blood
glucose level. This might be due to the activity of extracts of
natural ingredients which are multicomponent mixtures so
that the effects of these components can be synergistic,
additive or antagonistic13,14.
290
Asian J. Sci. Res., 12 (2): 287-292, 2019
The results of other studies showed that a dose of
150 mg kgG1 b.wt. had the effect of lowering fasting blood
glucose level in white rats, better than the dose8 of
100 mg kgG1 b.wt.. Research conducted by Sintowati
et al
.8
also showed that the higher doses of avocado leaf extract can
reduce the fasting blood glucose level better than the low
doses. Other studies have shown that avocado leaf extract
with 1.960 kg b.wt., can reduce the glucose of 64.27% and
there is no significant difference compared to the positive
control glipizid15 is 68.50%.
The decrease in blood glucose level by giving avocado
leaf extract showed that the anti-oxidant content of avocado
leaf extracts such as flavonoids and tannins had the effect of
lowering blood glucose level in test animals. Qualitative
analysis of phytochemical compounds on avocado leaf extract
shows that it contains flavonoid compounds, saponins,
tannins, triterpenoids, steroids and no alkaloids10. Flavonoids
contained in avocado leaves (
Persea americana
Mill) acts as
hypoglycemic agents16. Saponins work by inhibiting the action
of the enzyme "-glucosidase, an enzyme in the intestine
which functions to convert carbohydrates into glucose17.
The role of tannins is to capture free radicals and reduce
increased oxidative stress in diabetics to control blood glucose
level18.
The implication of this study is that avocado leaf extract
can be used to reduce fasting blood glucose level with the
recommended dose of 150 mg kgG1 b.wt. This study is a
preclinical test. Therefore, further research on humans is
needed to get a positive effect of the extract on humans,
especially patients with high fasting blood glucose level. In
terms of research limitations, which anti-oxidant compounds
in avocado leaves that have the ability as anti-diabetic to
reduce blood glucose level has not been known.
CONCLUSION
Avocado leaf extract can reduce high fasting blood
glucose level in test animals after intervention for 7 days and
14 days at a dose of 150 mg kgG1 b.wt. This preclinical test
shows that dosing of avocado leaf extract that is too low and
high does not have a positive effect in reducing fasting blood
glucose level.
SIGNIFICANCE STATEMENT
This study reveals that avocado leaf extract with its
phytochemical content and antioxidant activity can reduce
fasting blood glucose level in white rats. This study will help
researchers determine the right dose of avocado leaf extract
significantly reduces the fasting blood glucose level in white
rats. This suggests that a high dose of avocado leaf extract in
white rats does not significantly decrease the fasting blood
glucose level.
ACKNOWLEDGMENT
The researchers would like to thank the Directorate
General of Development and Research Enhancement of the
Ministry of Research, Technology and Higher Education for
research funds, the Chair of the Tadulako University Research
and Community Service Institution, the Head of the STIFA
Pharmacology Laboratory Pelita Mas Palu and the staffs and
students who helped the research.
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Article
Full-text available
This research aims to analyze the characteristics of maltodextrin capsules of avocado leaf extract. It was conducted in the Analytical Chemistry Laboratory of the Mathematics and Science Faculty of Tadulako University. The research variables are antioxidant power, anthocyanin content, phenolic content, tannin content, water content, and toxicity test in mice with various doses. It was found that the % inhibition of avocado leaf extract maltodextrin capsules increases with the increasing concentrations of 33.662%-51.996% with the IC50 value of 78.732. The phenolic, tannin and antiocyanin contents in maltodextrin capsules of avocado leaf extract on average are high by 39.94 mg/dL (Phenol), 59.54 mg/dL (Tannin), 0.0004 g/l (Anthocyanin) and low water solubility of 8.219%. The results of the toxicity test show that the administration of the avocado leaf extract maltodextrin capsules observed for 24 hours did not obtain data on the death of the test animals. It is concluded that the avocado leaf extract maltodextrin capsule has high antioxidant power with high anthocyanin, phenolic and tannin contents that can be used as a product rich in antioxidant content.
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