Evaluation of Antioxidant Capacity by Cyclic
Voltammetry of Phoenix dactylifera L. (date palm)
Assia Belfar1,2*, Cheyma Bensaci1,2,
Mahdi Belguidoum1,3
1Laboratory
of Valorization and Promotion of Saharan Resources, Kasdi Merbah University, 30000
Ouargla, Algeria.
2Department
of Exact Sciences, Higher Normal School of Ouargla, 30000 Ouargla, Algeria.
3Department of Agronomy, Faculty of Nature and Life
Sciences and Earth Sciences, University of Ghardaia, 47000 Ghardaia, Algeria.
*Corresponding Author E-mail: probelfarassia@gmail.com
In
this study we used spectrophotometrical techniques to estimate antioxidant
efficacy by using 2,2-diphenyl-1-picrylhydrazyl free radical scavenging
capacity and reducing power capacity. We have used also electrochemical
techniques performed by cyclic voltammetry. The present study examined the
antioxidant activities of the methanolic extract (ME) of date palm (Phoenix dactylifera.
L) fruits (DPF) of four native cultivars from Algeria, namely, Ghars (Gh),
Chtaya (Cht), Degla Beďda (DB) and Tinissine (Tns). Quantitative estimation of
total phenol and flavonoid content by a colorimetric assay showed that methanol
extracts are rich in these components. The content of total phenolics of
different cultivars extracts was in the range of 26.083 - 35.850 GAE/100g DW.
while it was the content of total flavonoids of the different cultivars
extracts was in the range of 5.276 - 6.055 QE/100g DW. The value of IC50
for DPPH radical test ranged from 0.193 to 0.400mg/ml. All extracts showed very
good activity of ferric reducing power, the higher power was in methanolic
extract of Tns. The less IC50 value in cyclic voltammetry method
(CV), which meet the highest effective antioxidant was 0.121 mg/ml in
methanolic extract of Tns.
INTRODUCTION:
Date palm (Phoenix
dactylifera L), cultivated in the arid and semi-arid regions since the foot
for its edible sweet fruits it is an important crop1, and very popular in Algeria2, Dates are produced in 35 countries worldwide and
cultivates on about 2.9million acres of land. In Algeria is an important tree
for people and plays principal roles in social, economic and environmental
sectors. As production Algeria is one of the first producers of the fruits of
the date in the world with 50000 t per year3 Antioxidants help organisms deal with oxidative
stress, caused by free radical damage.
Free radicals are chemical species, which contains one
or more unpaired electrons due to which they are highly unstable and cause
damage to other molecules by extracting electrons from them in order to attain
stability4, and they are harmful by-products generated during
normal cellular metabolism, which could initiate oxidative damage in the body5. Polyphenols of plant origin like catechins exert
anticarcinogenic, antimutagenic and cardioprotective effects, which is
attributed to their free radical scavenging activity6. Ripe date fruits have high antioxidant activity as a
result of a relatively high vitamin and phytochemicals content such as
polyphenols7. Most determinations of total antioxidant activity of
phenolic compounds in dates are performed on alcohol or acetone extracts8.
MATERIAL
AND METHODS:
Chemicals:
Commercially
available chemicals were used without any further purification. Methanol
(99%), ethyl acetate (C4H8O2), ammonium
sulphate [(NH4)2SO4], phosphoric acid (H3PO4),
sodium hydroxide NaOH, Folin-Ciocalteu reagent, sodium carbonate Na2CO3, sodium nitrite NaNO2,
aluminum chloride AlCl3, Gallic acid (GA), quercetin (QC),Ascorbic
acid (AAsc), butylatedhydroxytoluene (BHT) C15H24O, butylatedhydroxyanisole
(BHA) C11H16O2, [K3Fe (CN)6],
ferric chloride (FeCl3), DPPH.
Collection
and identification:
Four
different ripe date palm (Phoenix dactylifera L.) fruit varieties (DPF),
Ghars (Gh), Chtaya (Cht), Degla Beďda (DB) and Tinissine (Tns) varieties were
harvested in October 2013. Fruits were collected from the National Institute of
Agronomic Research Touggourt-Algeria (INRAA).
Sample preparation and extraction:
After
washing with water and removing the seeds, the edible part of date cut to small
pieces using a scissor and dried at room temperature. The extraction of
antioxidant compounds from the date cultivar was carried using the methanol as
described by Marie-Josphe Amiot et al9, with slight modifications by BENSACI et al10. Ten grams of sample were mixed for 24 h with 100ml
of methanol/H2O (8/2) at room temperature with agitation. The
mixture was centrifuged at 3500 × g for 15min, and the supernatant was filtered
using filter paper. The filtrates of hydro-alcoholic were combined. After
removing the alcohol under vacuum at 40°C, the phenolic compounds were
extracted thrice with ethyl acetate in the presence of an aqueous solution
containing 20% ammonium sulphate and 2% of Phosphoric acid solution. The three
organic phases evaporated to dryness using a rotary evaporator. The extracted
phenolics were dissolved in a certain volume of methanol.
Determination of TPC:
TPC
of the date extracts was identified using the Folin–Ciocalteu method11. The extract (200
) was mixed with 1.5ml of Folin-Ciocalteu reagent
(previously diluted 10-fold with distilled water) for 5 min at room
temperature. 1.5ml of aqueous Na2CO3(60g/l) was added,
and the mixture was vortexed and allowed to stand at room temperature. After 90
min, the absorbance was measured at 725nm. The TPC was calculated from standard
gallic acid curve and expressed as milligrams of gallic acid equivalents per
100g of dry weight of date for three replicates (mg GAE/ 100g DW).
Determination of TFC:
TFC
of the date extracts was measured according to the colorimetric assay12, with slight modifications. 150 of the extract were added to 150 NaNO2 (5%) followed by 300 AlCl3 (10%). Test tubes were incubated at
room temperature for 5 min, and then 1ml of 1 M NaOH, was added. The absorbance
of the mixture was determined at 510nm. TFC was determined from standard
quercetin curve and expressed milligrams of quercetin equivalents per 100g of
dry weight of date for three replicates (mg QE/100g DW).
Evaluation of antioxidant capacity by
spectrophotometrical techniques:
Ferric reducing power (FRP):
The
reducing power of the solvent extract was determined by the method of13, with slight modifications. Each extract (1ml) was
mixed with 2.5ml of phosphate buffer (0.2mol/l, pH 6.6) and 2.5ml of K3Fe
(CN)6 (1%). The mixture was incubated at 50◦C for
20 min. Then, 2.5ml of 10% TCA were added to the mixture. 2.5ml of solution was
mixed with 2.5ml of distilled water and 0.5ml of 0.1% FeCl3, and the
absorbance was read at 700nm against a blank. All analyses were carried out in
triplicate. Reducing power was expressed mM as ascorbic acid equivalents
antioxidant capacity (AEAC). BHA and BHT were used as standard controls.
Increased absorbance of the reaction mixture indicates increased reducing
power.
DPPH scavenging capacity:
The
free radical scavenging activity of the extract was measured in terms of
hydrogen donating or radical scavenging ability using the stable free radical
DPPH according to the method explained by14, with slight modifications. 150µl of Different
concentrations of the extract were added to 3.0ml 0.1 mM DPPH solution in
methanol. After mixing vigorously the tubes were incubated in dark. After 30
min the absorbance was measured at 517nm. IC50 value (the
concentration required to scavenge 50% DPPH free radicals) was calculated from
the concentration versus scavenging activity curve. BHT and BHA were used as
positive control. The capability to scavenge the DPPHR was
calculated using the following equation:
DPPH
scavenging activity (%) = ((A0 – A1) / A0) 
100
Where
A0 is the absorbance in the absence of sample and A1 is
the absorbance in the presence of the sample.
Evaluation
of antioxidant capacity by electrochemical techniques:
There
are many studies that include this method15, 16.
Cyclic voltammetric (CV) measurements were performed using a Voltalab 40 model
PGZ301 (Radiometer Analytical) potentiostat/galvanostat driven by a personal
computer with Volta Master 4 software. The electrochemical cell (V=25ml)
consists of three electrodes immersed in a solution containing the analyte and
an excess of supporting electrolyte. A glassy carbon electrode (Ř_3.0mm) as the
working electrode, a platinum wire was used as the auxiliary electrode, and a
saturated calomel electrode (SCE) as the reference electrode respectively. The potential was swept in inverse scanning mode
starting from 0 to -1.6 V with a scanning rate of 0.1Vs−1 to avoid reducing the sensitivity of the working electrode.
To
estimate the total antioxidant capacity of the DPF extracts, we have used the
cyclic voltammetry following the method of Bourvellec, et al.17 with slight modification. The effect of various
extracts was checked by the method of the proportioned additions and the
successive addition of 100μl of initial solution of extract to the 25ml
oxygen solution in order to get an antioxidant substrate concentration in the range
(0-0.010 g/l) Gh, (0-0.004g/l) Cht, (0-0.006g/l) DB and (0-0.008 g/l) Tns.
After each aliquot addition, CV of the oxygen solution was recorded at a scan
rate 0.1Vs−1. The total antioxidant capacity of scavenging on
superoxide radical was calculated using the following equation:
Where
and 
are the anodic peak current of O2•−oxidation with and without the DPF extracts.
Statistical
analysis:
All
experiments were repeated three times. All values were expressed as mean and
standard deviation. The difference between the values as analyzed by one-way
analysis of variance (ANOVA).
RESULTS
AND DISCUSSION:
Determination
of TPC:
The
TPC was determined in methanolic extract of tested date cultivars. As shown in
Table 1. There were significant differences (P < 0.01) between the
cultivars. Values for TPC vary from 26.083 to 35.850 mg acid gallic equivalents
(GAE/100 g DW sample). The highest TPC was in Cht date and the lowest TPC was
in Gh date. The order of TPC content was as follow: Gh < DB < Tns <
Cht (Figure 1).
The
present results were much higher compared to TPC content of Algerian date
fruits from Ghardaia in a study conducted by Mansouri Abdelhak et al. 2.49 to
8.36 mg GAE/100 g FW 18, Eimad dine Tariq Bouhlali et al in date cultivars
consumed in Morocco ranged between 2.697 to 5.342 g GAE/100 g 19. Same rounding values that ranged from 32.24 mg to
35.84 mg GAE/100 g DE were reported by Hachani et al 20. Higher TPC values were found by Fatma Mihoub et al.21, Ebtesam Abdullah Saleh et al. 22. These authors reported that the TPC reached up to
66.1-189 mg GAE/100 g FW and 106.06-455.88 mg/100g, respectively. The observed
differences may mainly be attributed to the cultivars and extraction conditions
such as solvent and ratio material/solvent.23
Determination
of TFC:
The
TFC was determined in methanolic extract of tested date cultivars. As shown in
Table 1. There were significant differences (P < 0.01) between the
cultivars. Values for TFC vary from 5.276
to 6.900mg quercetin
equivalents (QE /100 g DW sample). The
highest TFC was in DB date and the lowest TFC was in Gh date. The order of TFC
content was as follow: Gh < Tns < Cht < DB (Figure 2).
The present study showed that the Algerian date palm
have higher flavonoid content compared to the other studies, such like the
study of Ismail Hamad et al. on date cultivars consumed in Saudi Arabia, ranged
between 1.22 and 2.82 mg/100 g DW 24. On Other side, higher TFC values were found such
like the study of Mohammed Al-Mamary et al where TFC ranged between 170 – 290
mg QE/100 g DW 25.These differences may be due to the cultivars, climate, cultivation practices
and extraction procedure.23
Table 1. Totalphenolic
content (TPC), total
flavonoid content (TFC), and antioxidant activities in different DPF Samples.
|
Sample
|
TPC
(mg )GAE/100g
DW)
|
TFC
(mg QE/100g
DW)
|
AEAC
(mM)
|
DPPH radical Scavenging activity IC50(mg/ml)
|
Superoxide anion
radical
scavenging activity IC50(mg/ml)
|
|
Gh
|
26.083±0.322*
|
5.276±0.149*
|
4.237±0.053*
|
0.400±0.012*
|
0.210*
|
|
Cht
|
35.850±0.627
|
6.230±0.213
|
5.260±0.108
|
0.210±0.002
|
0.127
|
|
DB
|
31.383±0.225
|
6.900±0.255
|
5.385±0.101
|
0.193 ±0.040
|
0.130
|
|
Tns
|
35.195±0.497
|
6.055±0.070
|
7.600±0.112
|
0.213±0.007
|
0.121
|
Each
value represents the mean and S.D. Statistical analysis was performed using the
one-way ANOVA. *p < 0.01.
Figure 1. Total phenolic content (mg GAE / 100 g DW).
Figure 2. Total flavonoid content (mg QE / 100 g DW)
Evaluation
of antioxidant capacity by spectrophotometrical:
Ferric reducing power (FRP):
Reducing
power is one of the mechanisms of antioxidant capacity which measure the
conversion of a Fe3+ ferricyanide complex to the ferrous form.
Substances, which have reduction potential, react with potassium ferricyanide
(Fe3+) to form potassium ferrocyanide (Fe2+), which then
reacts with ferric chloride to form ferric ferrous complex that has an
absorption maximum at 700nm26. The antioxidant activity was expressed as AEAC
value. As shown in Table 1, all cultivars exhibited a good reducing power which
varied significantly (P < 0.01) from 4.237 to 7.600mM for Gh and Tns, respectively. The present findings, were in agreement with another
study carried out by Ghiaba Zineb al. on date cultivars consumed in Algeria27
The order of antioxidant screening all cultivars
exhibited was as follow: DB > Cht > Tns > Gh (Figure 3).
The reducing capacity of a compound may serve as a
significant indicator of its potential antioxidant activity. The reducing power
of the extract might be due to their hydrogen donating ability which can be
attributed to the reductants present28.
Figure 3. AEAC values of ascorbic acid equivalents antioxidant
capacity of extracts.
DPPH scavenging capacity:
The DPPH test is a method widely used in the analysis
of antioxidant activity. Originally, DPPH• is a stable free radical. This
stability is due to the delocalization of free electrons within the molecule
DPPH•. The presence of these DPPH• radicals gives rise to a dark violet
coloring of the solution, which absorbs around 517nm. The reduction of the
DPPH• radicals by an antioxidant causes discoloration of the test solution29.
The
antioxidant activity of dates extracts measured by the DPPH method showed that
all varieties had an important free radical scavenging ability. As it is known,
lowest IC50 values indicates a higher antioxidant power. The IC50
values of samples ranged from 0.193 to 0.400 mg/ml (Table 1). In addition, an
extract is considered to be active against free radicals if IC50<
5mg/ml30. All our extracts have IC50 values <5
mg/ml, therefore all the extracts considered to be active against free
radicals. These results were in line with those of Ghiaba Zineb al. On date
cultivars consumed in Algeria27 and Bushra Sultana et al. On date cultivars consumed
in Pakistan31 who also reported that date fruits exhibited potent
DPPH scavenging capacities.
The
order of antioxidant of all cultivars was as follow: DB > Cht > Tns >
Gh (Figure 4).
The
presence of free hydroxyl group in the aryl moiety is one of the factors in
determining the DPPH scavenging activity of the compound is also described
where protection of the free hydroxyl group drastically reduced the DPPH
scavenging activity32.
Figure 4. IC50 values of DPPH assay for free radical
scavenging activity of extracts.
Evaluation
of antioxidant capacity by electrochemical techniques:
The
major limitation of spectrophotometric methods used in the measurement of
antioxidant activity is the interference of biomolecules that absorb in the
same wavelength. Therefore, search of other methods based on different
principle is necessary. Voltammetric method is one of these novel tools as
speed, cheaper, simple, consuming fewer reagents and depending mostly on the
electrochemical properties of antioxidants. In addition, it is well established
that electrochemical methods are considered as simple methods for the right
evaluation of the total amounts and the types of polyphenols in vegetables and
plants. Furthermore, these techniques have been capable to give the global
amount of different types of polyphenols in the same time and to characterise new
compounds containing polyphenols which could play important role in food and
pharmaceutical industry.33
The
obtained results (Figure.5) show that in all addition of the extract causes a
proportional decrease of O2•− anodic peak current 
while the intensity of O2cathodic current
appears to be fixe in the majority of the extracts (Figure.5). The decrease of
the anodic peak current of O2•− suggests that the
polyphenol substrate reacts irreversibly with O2•−.
Figure 5. Plotting
of scavenging of superoxide anion of cyclic voltammogram against the
corresponding concentration of DPF extracts. Operative condition: DMF + 0.1M
Bu4NPF6 on GC as working electrode vs. SCE at 28°C with scan rate of 0.1 V/s.
The
activity of the antioxidant is often evaluated according to its IC50,
it is defined by the concentration inhibiting the reaction by 50%. In this
system, which were calculated from the linear regression of the % antioxidant
activity versus extracts concentrations. Results shown in Figure 7 as described
in Table 1.Lower values correspond to higher antioxidant activities. It can be
seen from this table the IC50 values of Tns extract (0.121 mg/ml)
showed an antioxidant capacity higher than other varieties extracts.
The
antioxidant activity in the methanolic extracts of DPF decreases in the order
Gh < DB < Cht < Tns. The present results were Much less compared to
the results of the study by cheyma bensaci et al. (2021) 34 which found IC50 value ranged between
0.006 - 0.012 mg /ml34. These differences may be due to the cultivars,
climate, cultivation practices and extraction procedure 23.
Figure 6. Concentration-response plots for inhibition
of the absorbance of Superoxide
anion radical for DPF extracts.
Figure 7. IC50 values of DPPH assay for free radical
scavenging activity of extracts.
CONCLUSIONS:
The
contents of phenolic compounds and the antioxidant activities of methanolic
extracts of DPF from four varieties from the Touggourt region in the South of
Algeria were evaluated. In this study, it was demonstrated that the methanol
extracts of DPF contain a considerable quantity of phenolic compounds, because
the choice of extraction solvent has great potential effect on the recovery of
phenolics and their quantities. Different employed assays, spectrophotometrical
(FRP and DPPH) and electrochemical assays showed that all varieties possess a
good antioxidant activity, which has clearly shown by strong IC50
values.
ACKNOWLEDGEMENTS:
The authors would like to thank director of
laboratory V.P.R.S in university of Ouargla, director of laboratory
V.T.R.S in university of
El Oued and National Institute of
Agronomic Research Touggourt-Algeria (INRAA).
REFERENCES:
1.
F.Z. Bentebba,
G. Zineb, and M. Saidi, Phytochemical content and Antioxidant properties of
Ghars date palm (Phoenix dactylifera L.) harvested at different stages of
maturity. Asian Journal of Research in Chemistry 2020.13(5): 323-326. doi.
10.5958/0974-4150.2020.00062.0
2. S. Zeroual, I. Daoud, R. Gaouaoui, and S. Ghalem, In
vitro and Molecular Docking Studies of DPPH with Phoenix dactylifera
L.(Deglet-Nour) Crude Fruits extracts and Evaluation of their Antioxidant
Activity. Asian Journal of Research in Chemistry 2020.13(1): 52-59. doi.
10.5958/0974-4150.2020.00012.7
3. M. Abdeldjabbar, D. Messaouda, R. Zhour, and B. Cheyma,
Comparative Analysis of Total Phenolics, Flavonoid content and Antioxidant
profile of date palm (Phoenix dactylifera L.) with different watering water
from Oued Soufin Algeria. Asian Journal of Research in Chemistry 2020.13(1):
28-32. doi. 10.5958/0974-4150.2020.00007.3
4. S.K. Sripathi and P. Lalitha, Electrochemical Behavior
of the Aqueous Fraction of the Ethanol Extract of Pisonia grandis (R. Br) at
Glassy Carbon Electrode. Asian Journal of Research in Chemistry 2011.4(5):
775-778. doi. 10.5958/0974-4150
5. á.E. Jose and á.P. Selvam, Identification of
Phytochemical Constituents in the Leaf Extracts of Azimaátetracantha Lam using
Gas Chromatography-Mass Spectrometry (GC-MS) analysis and Antioxidant Activity.
Asian Journal of Research in Chemistry 2018.11(6): 857-862.
doi.10.5958/0974-4150.2018.00150.5
6. P. Shlini and K. Murthy, Extraction of phenolics,
proteins and antioxidant activity from defatted tamarind kernel powder. Asian
Journal of Research in Chemistry 2011.4(6): 936-941. doi. 10.5958/0974-4150
7. N.A. AlFaris, J.Z. AlTamimi, F.A. AlGhamidi, N.A.
Albaridi, R.A. Alzaheb, D.H. Aljabryn, A.H. Aljahani, and L.A. AlMousa, Total
phenolic content in ripe date fruits (Phoenix dactylifera L.): A systematic
review and meta-analysis. Saudi Journal of Biological Sciences 2021
doi.org/10.1016/j.sjbs.2021.03.033
8. M.Z. Alam, M.S. Alhebsi, S. Ghnimi, and A. Kamal-Eldin,
Inability of total antioxidant activity assays to accurately assess the
phenolic compounds of date palm fruit (Phoenix dactylifera L.). NFS Journal
2021.22: 32-40. doi.org/10.1016/j.nfs.2021.01.001
9. M.J. Amiot, A. Fleuriet, and J.J. Macheix, Importance
and evolution of phenolic compounds in olive during growth and maturation.
Journal of Agricultural and Food Chemistry 1986.34(5): 823-826.
doi.org/10.1021/jf00071a014
10. C. Bensaci, Z. Ghiaba, M. Dakmouche, M. Saidi, M.
Hadjadj, A. Belfar, and M. Belguidoum, Studies on Antibacterial Compounds from
Methanolic Extracts of Date Palm (Phoenix dactylifera L.) fruits from Algeria.
Asian Journal of Research in Chemistry 2019.12(6): 338-340. doi.
10.5958/0974-4150.2019.00063.4
11. M. Al-Farsi, C. Alasalvar, A. Morris, M. Baron, and F.
Shahidi, Comparison of antioxidant activity, anthocyanins, carotenoids, and
phenolics of three native fresh and sun-dried date (Phoenix dactylifera L.)
varieties grown in Oman. J Agric Food Chem 2005.53(19): 7592-9.
doi.org/10.1021/jf050579q
12. D.-O. Kim, S.W. Jeong, and C.Y. Lee, Antioxidant
capacity of phenolic phytochemicals from various cultivars of plums. Food
Chemistry 2003.81(3): 321-326. doi.org/10.1016/S0308-8146(02)00423-5
13. A. Kumaran and R. Joel Karunakaran, In vitro
antioxidant activities of methanol extracts of five Phyllanthus species from
India. LWT - Food Science and Technology 2007.40(2): 344-352.
doi.org/10.1016/j.lwt.2005.09.011
14. R.S. Govardhan Singh, P.S. Negi, and C. Radha, Phenolic
composition, antioxidant and antimicrobial activities of free and bound phenolic
extracts of Moringa oleifera seed flour. Journal of Functional Foods 2013.5(4):
1883-1891. doi.org/10.1016/j.jff.2013.09.009
15. Z. Ghiaba, M. Yousfi, M. Hadjadj, and M. Saidi, Study
of antioxidant properties of five Algerian date (phoenix dactylifera L)
cultivars by cyclic voltammetric technique. 2014
16. N.G. Etsassala, T. Waryo, O.K. Popoola, A.O. Adeloye,
E.I. Iwuoha, and A.A. Hussein, Electrochemical screening and evaluation of
lamiaceae plant species from South Africa with potential tyrosinase activity.
Sensors 2019.19(5): 1035. doi.org/10.3390/s19051035
17. C. Le Bourvellec, D. Hauchard, A. Darchen, J.-L.
Burgot, and M.-L. Abasq, Validation of a new method using the reactivity of
electrogenerated superoxide radical in the antioxidant capacity determination
of flavonoids. Talanta 2008.75(4): 1098-1103. doi.
10.1016/j.talanta.2008.01.007
18. A. Mansouri, G. Embarek, E. Kokkalou, and P. Kefalas,
Phenolic profile and antioxidant activity of the Algerian ripe date palm fruit
(Phoenix dactylifera). Food Chemistry 2005.89(3): 411-420.
doi.org/10.1016/j.foodchem.2004.02.051
19. C. Alem, J. Ennassir, M. Benlyas, A.N. Mbark, and Y.F.
Zegzouti, Phytochemical compositions and antioxidant capacity of three date
(Phoenix dactylifera L.) seeds varieties grown in the South East Morocco.
Journal of the Saudi Society of Agricultural Sciences 2017.16(4): 350-357.
doi.org/10.1016/j.jssas.2015.11.002
20. S. Al Harthi, A. Mavazhe, H. Al Mahroqi, and S.A. Khan,
Quantification of phenolic compounds, evaluation of physicochemical properties
and antioxidant activity of four date (Phoenix dactylifera L.) varieties of
Oman. Journal of Taibah University Medical Sciences 2015.10(3): 346-352.
doi.org/10.1016/j.jtumed.2014.12.006
21. F. Mihoub, F. Gourchala, and S. Toumi, Bioactivity of
Algerian palm dates Phoenix dactylifera L. Ukrainian food journal 2019(8, Issue
2): 249-259. doi. 10.24263/2304- 974X-2019-8-2-5
22. 22. E.A. Saleh, M.S. Tawfik, and H.M. Abu-Tarboush,
Phenolic contents and antioxidant activity of various date palm (Phoenix
dactylifera L.) fruits from Saudi Arabia. Food and Nutrition Sciences 2011.2011
doi. 10.4236/fns.2011.210152
23. Z. Benmeddour, E. Mehinagic, D. Le Meurlay, and H.
Louaileche, Phenolic composition and antioxidant capacities of ten Algerian
date (Phoenix dactylifera L.) cultivars: a comparative study. Journal of
Functional Foods 2013.5(1): 346-354. doi.org/10.1016/j.jff.2012.11.005
24. I. Hamad, H. AbdElgawad, S. Al Jaouni, G. Zinta, H.
Asard, S. Hassan, M. Hegab, N. Hagagy, and S. Selim, Metabolic analysis of
various date palm fruit (Phoenix dactylifera L.) cultivars from Saudi Arabia to
assess their nutritional quality. Molecules 2015.20(8): 13620-13641.
doi.org/10.3390/molecules200813620
25. M. Al-Mamary, M. Al-Habori, and A.S. Al-Zubairi, The in
vitro antioxidant activity of different types of palm dates (Phoenix
dactylifera) syrups. Arabian Journal of Chemistry 2014.7(6): 964-971.
doi.org/10.1016/j.arabjc.2010.11.014
26. M. Singhal, A. Paul, and H.P. Singh, Synthesis and
reducing power assay of methyl semicarbazone derivatives. Journal of Saudi
Chemical Society 2014.18(2): 121-127. doi.org/10.1016/j.jscs.2011.06.004
27. G. Zineb, M. Boukouada, A. Djeridane, M. Saidi, and M.
Yousfi, Screening of antioxidant activity and phenolic compounds of various
date palm (Phoenix dactylifera) fruits from Algeria. Mediterranean Journal of
Nutrition and Metabolism 2012.5(2): 119-126. doi.10.1007/s12349-011-0082-7
28. J. Elias, M. Rajesh, N. Anish, P. Deepa, and N. Jayan,
In vitro antioxidant activity of the methanolic extract of Simaruba glauca DC.
Asian Journal of Research in Chemistry 2010.3(2): 312-315.
29. F. Guemari, S.E. Laouini, A. Rebiai, and A. Bouafia,
Phytochemical screening and Identification of Polyphenols, Evaluation of
Antioxidant activity and study of Biological properties of extract Silybum marianum
(L.). Asian Journal of Research in Chemistry 2020.13(3): 190-197. doi.
10.5958/0974-4150.2020.00037.1
30. S. Hachani, C. Hamia, S. Boukhalkhal, A.M. Silva, A.
Djeridane, and M. Yousfi, Morphological, physico-chemical characteristics and
effects of extraction solvents on UHPLC-DAD-ESI-MSn profiling of phenolic
contents and antioxidant activities of five date cultivars (Phoenix dactylifera
L.) growing in Algeria. NFS journal 2018.13: 10-22.
doi.org/10.1016/j.nfs.2018.10.001
31. B. Sultana, B. Fatima, and M. Mushtaq, In vitro
synergism of antimutagenic and antioxidant activities of Phoenix dactylifera
fruit. Food Science and Biotechnology 2014.23(3): 881-887. doi.
10.1007/s10068-014-0118-0
32. S. Malik and A. Choudhary, Anti-Oxidant Activity of
Novel 5-Substituted Arylidene-3-SubstitutedBenzyl-Thiazolidine-2, 4-Diones.
Asian Journal of Research in Chemistry 2011.4(1): 120-122.
33. S. Amamra, M.E. Cartea, O.E. Belhaddad, P. Soengas, A.
Baghiani, I. Kaabi, and L. Arrar, Determination of total phenolics contents,
antioxidant capacity of Thymus vulgaris extracts using electrochemical and
spectrophotometric methods. Int. J. Electrochem. Sci 2018.13(8): 7882-7893 . doi: 10.20964/2018.08.57
34. C. Bensaci, Z. Ghiaba, M. Dakmouche, A. Belfar, M.
Belguidoum, F.Z. Bentebba, M. Saidi, and M. Hadjadj, In Vitro Evaluation of
Antioxidant Potential of Date Palm Collected in Algeria using Electrochemical
and Spectrophotometrical Techniques. Korean Chemical Engineering Research
2021.59(2): 153-158. doi. 10.9713/kcer.2021.59.2.153