Cucumber peel - Antioxidant and antimicrobial activity

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IN VITRO ANTIOXIDANT AND ANTIMICROBIAL PROPERTIES OF CUCUMIS SATIVUS L. PEEL
EXTRACTS
Sheila John 1*, Priyadarshini S 1, Sarah Jane Monica 1, Sivaraj C 2, Arumugam P 2
1Department of Home Science, Women’s Christian College, Chennai, India
2Armats Biotek Research and Training Institute Chennai, India
*Corresponding Author Email: sheila.research16@gmail.com
Article Received on: 28/12/17 Approved for publication: 12/01/18
DOI: 10.7897/2230-8407.0918
ABSTRACT
The present study evaluated the phytochemicals, antioxidant and antimicrobial potential; and thin layer chromatographic studies of Cucumis sativus L.
peel extracts. The total flavonoid content was assessed using Aluminium Chloride reagent method. The antioxidant potential was evaluated using in
vitro assays viz DPPH radical scavenging assay, FRAP and Phosphomolybdenum assay. The antimicrobial activity was determined against Shigella
flexneri, E coli, Staphylococcus aureus and Klebsiella pneumonia using Agar Well Diffusion method. Qualitative phytochemical anal ysis confirmed
the presence of alkaloids, saponins, diterpenes, steroids and flavonoids. Total Flavonoid content in the Cucumis sativus L. peel was 3.50 µg/mg QE.
Cucumis sativus L. peel showed highest radical scavenging activity of 71% at the concentration of 600 µg/mL. In determination of antioxidant activity
via FRAP and Phosphomolybdenum assay cucumber peel extract showed highest absorbance of 0.80 and 0.94 respectively at the concentration of 300
µg/mL. The peel extracts inhibited the growth of all the tested pathogens by forming inhibition zones ranging from 11-21 mm. Thin layer
chromatographic studies of the cucumber peel extracts constituted different coloured phytochemical compounds with different Rf values. This study
highlights the pharmacological properties of Cucumis sativus L. peel.
Keywords: Cucumis sativus L. peel, flavonoids, Antimicrobial, Antioxidant
INTRODUCTION
Cucumber (Cucumis sativus L.) belongs to Cucurbitaceae family
such as melon, watermelon, pumpkin and zucchini. It is widely
consumed fresh in salads or fermented (pickles) or as a cooked
vegetable1. They are widely used for various skin problems
including swelling under the eyes and sunburn. It is believed that
they promote refreshing, cooling, healing, soothing, emollient
and anti-itching effect to irritated skin2. The nutrient profile of
Cucumis sativus L. includes water (96.4%), protein (0.4%), fat
(0.1%), carbohydrate (2.8%), mineral (0.3%), calcium (0.01%),
phosphorus (0.03%), iron (1.5 mg/100 g) and vitamin B (30
IU/100 g). Ascorbic acid and Enzyme such as crepsin, proteolytic
enzyme, oxidase, succinic, malic dehydrogenase have also been
reported in the fruits3. The bioactive compounds isolated from
cucumber includes cucurbitacins, cucumegastigmanes I and II,
cucumerin A and B, vitexin, orientin, isoscoparin 2″-O-(6‴-(E)-
p-coumaroyl) glucoside, apigenin 7-O-(6″-O-p-
coumaroylglucoside)1,5.
Cucumber exhibits wide range of in vitro and in vivo
pharmacological effects. Cucumber extract showed antioxidant
activities against various assays including DPPH, reduction
assay, total oxyradical scavenging capacity (TOSC) assay, trolox
equivalent antioxidant capacity (TEAC), total radical-trapping
antioxidant parameter (TRAP) or ferric reducing-antioxidant
power (FRAP) assays6,7,8,9. Cucumis sativus L. fruit and seed
extracts are reported to have antibacterial and antifungal
activity10, 11. Cucumis satvis L. showed cytotoxic activity against
human cancer cell lines12. The fruit and peel of cucumber are
shown to have antidiabetic and hypocholesterolemic activity13, 14.
Dixit and Kar15 studied the glucose regulating role of Cucurbita
pepo, Cucumis sativus and Praecitrullus fistulosus peel extracts
in mice. The study reported that all the three peel extracts nearly
reversed most of the changes induced by alloxan suggesting their
possible role in ameliorating diabetes mellitus and related
changes in serum lipids. Gill et al16 reported that the cucumber
seed possess significant antiulcer potential owing to its
antioxidant activity.
The pharmacological properties of Cucumis sativus L. fruit and
seed have been extensively studied, but comparatively very few
studies have been reported on the therapeutic potential of
Cucumis sativus L. peel. Moreover, the plethora of waste
generated from food industry; recent interest in reaping bioactive
compounds from the waste generated from fruit and vegetable;
and consumers increasing demand for natural health benefitting
products are the rationale behind the present study. Therefore, the
present study aimed to identify the phytochemicals; and to
evaluate the antioxidant and antimicrobial activity of Cucumis
sativus L. peel.
MATERIALS AND METHOD
Preparation of peel extracts
Fresh mature cucumbers were purchased from the local market.
The cucumbers were washed thoroughly under running tap water
and were manually peeled using a sterilized peeler. The peels
were then shade dried at room temperature for 5 days. The shade
dried cucumber peels were powdered in a laboratory blender and
was kept in airtight bottles until further use. The powdered
cucumber peel was soaked in methanol and chloroform for 72 h
by maceration technique. The supernatant was filtered through

Sheila'John'et'al.'Int.'Res.'J.'Pharm.'2018,'9'(1)'
57#
Whatman No.1 filter paper and concentrated using rotary
evaporator and dry residue was preserved at 5°C in airtight bottles
until further use.
Qualitative phytochemical screening
The qualitative phytochemical tests were performed to screen the
presence of bioactive components in methanol and chloroform
extract of Cucumis sativus L. peel. The screening was performed
for triterpenes/steroids, alkaloids, anthraquinones, coumarins,
flavonoids, saponins, tannins, and phenolic acids according to
standard method17-21.
Estimation of total Flavonoid content by AlCl3 reagent
method
The total flavonoid content of peel extracts of Cucumis sativus L.
was determined by the AlCl3 reagent method22. The extract
(500µg/mL) was mixed with 0.5 mL of 5% NaNO2 solution and
allowed to stand for 5 mins. Then 0.3 mL of 10% AlCl3 solution
was added and the mixture was allowed to stand for further 5 min.
Finally, 1 mL of 1 M NaOH solution was added, and the final
volume of the mixture was brought to 5 mL with distilled water.
The mixture was incubated for 15 mins at room temperature and
absorbance was measured at 510 nm. The total flavonoid content
was expressed as quercetin equivalent (µg/mg of extract), which
is a common reference standard.
Antioxidant activity
DPPH (1,1-diphenyl-2-picryl-hydrazyl) radical scavenging
assay
The DPPH radical scavenging activity was carried out according
to the method described by Bloi s23. One mL of the peel extracts
was taken in of various concentrations and mixed with 1 mL of
0.1 mM of DPPH solution in methanol. The reaction mixture was
kept at room temperature for 30 min. Absorbance was read at 517
nm in spectrophotometer. The percentage of the radical
scavenging activity was calculated as follows.
% of inhibition = Control – Sample / Control × 100
FRAP (Ferric Reducing Antioxidant Power) assay
The Fe3+reducing power assay was done according to the method
described by Yen and Chen24. 10 mg of the Cucumis sativus L.
peel (methanol and chloroform extract) was taken in different
concentrations and were mixed with 1 mL of phosphate buffer
(0.2 M, pH 6.6) and 1 mL of potassium ferricyanide (1%).The
mixture was incubated at 50ºC for 20 min. 1 mL of 10%
trichloroacetic acid was added to the mixture. Then 1 mL of 0.1%
of freshly prepared ferric chloride was added and the absorbance
of the resultant solution was measured at 700 nm.
Phosphomolybdenum reduction assay
The antioxidant activity was evaluated by reduction assay method
by the formation of green phosphomolybdenum complex25. 1 mL
of various concentrations of the Cucumis sativus L. peel extracts
(methanol and chloroform extract) were combined with 1 mL of
reagent solution (0.6 M sulphuric acid, 28 mM sodium phosphate
and 4 mM ammonium molybdate). The tubes were capped and
incubated in a water bath at 95°C for 90 min. The samples were
cooled to room temperature and the absorbance of the mixture
was measured at 695 nm against blank.
Antibacterial activity
The antibacterial activity of the Cucumis sativus L. peel methanol
and chloroform extract was analysed by well diffusion method26.
Muller Hinton agar was prepared according to the standard
procedure and 25 mL was poured into the plates and was allowed
to solidify. The standard inoculum suspension was streaked over
the surface of the media using sterile cotton swab to ensure the
confluent growth of the organism and the plates were allowed to
dry for 5 minutes. After drying, the different concentrations (50,
75 and 100 µg/mL) of the methanol and acetone extract of
cucumber peel were poured into the wells. Tetracycline was used
as a standard (1 µg/mL) and methanol was used as control.
Finally, the inoculated plates were incubated for 24 hours at 37ºC
for bacteria. The zone of inhibition was measured and noted.
Thin Layer Chromatography
The thin layer chromatography method was performed for the
detection of active compounds, based on the results (Retention
factor) Rf value of the separated compounds can be calculated
easier. Thin layer chromatography (TLC) was performed on pre-
coated 20cm × 20cm and 0.25mm thickness. Aliquots of the
extract were spotted on the TLC plates which was 0.2 mm above
from the bottom with the help of a capillary tube. Then the sample
spotted sheets were placed in the respective solvent system
adopted as mobile phase. The solvent system used for methanol
extract was toluene: ethyl acetate: methanol in the ratio 1:0.8:0.2.
The solvent system used for chloroform extract was toluene: ethyl
acetate in the ratio 1.5:0.5. The spots in the chromatogram were
well observed.
RESULTS
Phytochemical Screening and Flavonoid estimation
The result of the phytochemical analysis showed that both the
Cucumis sativus L. peel extracts contained alkaloids, saponins,
diterpenes, and flavonoids. While steroids were present only in
methanol extract; glycoside was present only in chloroform
extract. The flavonoid content of Cucumis sativus L. peel
methanol extract was higher, i.e. 3.50µg/mg QE than chloroform
extract (0.88 µg/mg QE).
Antioxidant Activity
The antioxidant activity of the Cucumis sativus L. peel extracts
were investigated using in vitro assays namely DPPH Assay,
FRAP Assay and Phosphomolybdenum Assay.
DPPH Assay
DPPH is a stable free radical, which has been widely used in
phytomedicine for the assessment of scavenging activities of
bioactive fractions. The results of DPPH assay for Cucumis
sativus L. peel is presented in Table 1 and 2. The Cucumis sativus
L. peel chloroform extract showed better radical scavenging
activity than methanol extract. IC50 value with 381.6 µg/mL and
329 µg/mL were observed in methanol and chloroform extract
respectively.
The Rf value was calculated using the following formula
Rf = Distance travelled by the solute / Distance travelled by the
solvent

Sheila'John'et'al.'Int.'Res.'J.'Pharm.'2018,'9'(1)'
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FRAP Assay
Ferric ion reducing power assay measures the electron donating
capacity of an antioxidant. The result of FRAP assay is presented
in Table.3. The absorbance at 300 µg/mL concentration was 0.80
and 0.30 for Cucumis sativus L. peel methanol and chloroform
extract respectively. An increased absorbance is indicative of
higher reducing power; therefore, it is clear that methanol extract
had higher reducing power than chloroform extract.
Phosphomolybdenum assay
The result of Phosphomolybdenum assay is presented in Table 4.
From the Table, it can be inferred that chloroform extract had
greater activity (0.94) for phosphomolybdenum assay than the
Methanol extract of Cucumis sativus L. peel. The assay is based
on the reduction of Mo (VI) to Mo (V) by the sample analyte and
the subsequent formation of a green phosphate/Mo (V) complex
at acidic pH25.
Antimicrobial activity
The result of antimicrobial activity of Cucumis sativus L. peel
extracts are presented in table.5. Both the extracts had good
inhibitory activity against all the tested organisms viz Shigella
flexneri, E coli, Staphylococcus aureus and Klebsiella
pneumonia. The methanol extract showed inhibited diameter
zones (IDZ) ranging from 11-21 mm, with highest zone of
inhibition exhibited by Staphylococcus aureus. IDZ for
chloroform extract were in the range 12-17 mm.
Thin Layer Chromatography
The number of spots observed and their corresponding Rf values
are presented in table 6 and 7. Cucumis sativus L. peel Methanol
extract yielded four spots, while nine spots were identified for
chloroform extracts. Data obtained from TLC analysis helps in
selection of appropriate solvent system for separation of pure
compounds by column chromatography27.
Table 1: DPPH activity of Methanolic ex tract of Cuc umis sativus L.
peel
Sl.No
Concentration
(µg/mL)
% of Inhibition
1
50
13.43
2
100
19.65
3
150
21.14
4
200
23.7
5
250
28.1
6
300
39.3
Table 2: DPPH activity of chloroform Extract of Cucumis sativus L.
peel
Sl.No
Concentration
(µg/mL)
% of Inhibition
1
100
21.32
2
200
33.19
3
300
45.49
4
400
62.95
5
500
67.8
6
600
71.3
Table 3: FRAP assay of Methanolic and Chloroform extract of Cucumis sativus L. peel
Sl.No
Concentration
(µg/mL)
Absorbance at 700 nm
Methanol
Chloroform
1
50
0.67
0.02
2
100
0.72
0.10
3
150
0.73
0.14
4
200
0.75
0.25
5
250
0.76
0.26
6
300
0.80
0.30
Table 4: Phosphomolybdenum assay of Methanol and Chloroform extract of Cucumis sativus L. peel
Sl. No
Concentration
(µg/mL)
Absorbance at 695 nm
Methanol
Chloroform
1
50
0.69
0.51
2
100
0.73
0.86
3
150
0.83
0.88
4
200
0.85
0.92
5
250
0.88
0.93
6
300
0.91
0.94
Table 5: Antimicrobial activity of Methanol and Chloroform extract of Cucumis sativus L. peel
S.No
Cucumis sativus L. peel
Organisms
Zone of Inhibition (mm)
Extract
Standard
50 µL
75 µL
100 µL
1
Methanol
Shigella flexneri
27
12
13
15
2
E coli
29
11
16
18
3
Staphylococcus aureus
28
18
19
21
4
Klebsiella pneumonia
26
16
18
19
1
Chloroform
Shigella flexneri
28
12
13
16
2
E coli
29
14
15
16
3
Staphylococcus aureus
28
13
16
17
4
Klebsiella pneumonia
27
12
13
15

Sheila'John'et'al.'Int.'Res.'J.'Pharm.'2018,'9'(1)'
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Table 6: Rf value of Cucumis sativus L. peel methanol extract
Compounds observed
under UV @ 235nm
Rf value
1
0.76
2
0.63
3
0.52
4
0.47
Table 7: Rf value of Cucumis sativus L. peel chloroform extract
Compounds observed
under UV @ 235nm
Rf value
1
3.7
2
3.3
3
2.7
4
2.2
5
1.6
6
1.1
7
0.8
8
0.4
9
0.3
Figure 1: TLC of methanol extract of Cucumis sativus L. peel
Figure 2: TLC of chloroform extract of Cucumis sativus L. peel
DISCUSSION
The qualitative phytochemical analysis revealed the presence of
bioactive compounds in cucumber peel. In a study conducted by
Foong et al.,12 on cucumber peel phosphate buffer saline extracts
the presence of alkaloids, saponins, steroid and flavonoids was
confirmed, with the exception of diterpenes and glycoside shown
in the present study. This difference in result could be due to the
different solvent used. The cucumber peel has considerable
amount of flavonoids and can be considered as a cheap source of
flavonoids. Flavonoids have been reported to exert multiple
biological property including antimicrobial, antioxidant,
cytotoxicity, anti-inflammatory as well as antitumor activities28.
Although cucumber peel extracts exhibited poor free radical
scavenging potential, the peel had good reducing power. The
reductive capacity of a compound depends on the presence of
reductones, which exhibit antioxidative potential by breaking the
free radical chain and donating a hydrogen atom29. The results
obtained for FRAP assay confirms the presence of antioxidant
reductones in cucumber peel. The result obtained for
antimicrobial activity in the present study was contrary to the
study conducted by Foong et al12., 2015, where phosphate buffer
saline cucumber peel extracts was only active against
Staphylococcus aureus (inhibition zone of 7.0±0 mm). Therefore,
from the present study it can be concluded that cucumber peel
possesses bioactive compounds; and has good antioxidant and
antimicrobial activity.
0.63
0.47
0.76
0.52
0.3
0.4
0.8
1.1
1.6
2.2
2.7
3.3
3.7

Sheila'John'et'al.'Int.'Res.'J.'Pharm.'2018,'9'(1)'
60#
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Cite this article as:
Sheila John et al. In vitro antioxidant and antimicrobial
properties of Cucumis sativus L. peel extracts. Int. Res. J.
Pharm. 2018;9(1): 56-60 http://dx.doi.org/10.7897/2230-
8407.0918
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