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Vegetable and fruit peels as a novel source of antioxidants

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Consumers are currently demanding less use of chemicals or minimally processed fruits and vegetables, so more attention had been paid to search for naturally occurring substances. This is particularly true for plant materials that act as alternative antioxidant sources. From this point of view, the present study was designed to evaluate the antioxidant potential of seven fruit and vegetable peels from India. Extraction was done individually by cold percolation method using various organic solvents (hexane, chloroform, acetone and methanol). Quantitative phytochemical analysis was done for total phenol and flavonoid content. Antioxidant testing assays were 2,2-diphenyl-1-picryl-hydrazyl (DPPH) free radical scavenging assay, hydroxyl radical scavenging assay, superoxide anion radical scavenging assay and reducing capacity assessment. Amongst the seven plant peels, the acetone extract of Mangifera indica was the most potent and in some cases even better than the standard. The results obtained indicate that M. indica peel may become important as a cheap and noticeable natural source of compounds with health protective potential, which can be used in pharmaceutical, nutraceutical and food preparation.
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Journal of Medicinal Plants Research Vol. 5(1), pp. 63-71, 4 January, 2011
Available online at http://www.academicjournals.org/JMPR
ISSN 1996-0875 ©2011 Academic Journals
Full Length Research Paper
Vegetable and fruit peels as a novel source of
antioxidants
Rakholiya Kalpna, Kaneria Mital and Chanda Sumitra*
Phytochemical, Pharmacological and Microbiological Laboratory, Department of Biosciences, Saurashtra University,
Rajkot-360 005, Gujarat, India.
Accepted 2 November, 2010
Consumers are currently demanding less use of chemicals or minimally processed fruits and
vegetables, so more attention had been paid to search for naturally occurring substances. This is
particularly true for plant materials that act as alternative antioxidant sources. From this point of view,
the present study was designed to evaluate the antioxidant potential of seven fruit and vegetable peels
from India. Extraction was done individually by cold percolation method using various organic solvents
(hexane, chloroform, acetone and methanol). Quantitative phytochemical analysis was done for total
phenol and flavonoid content. Antioxidant testing assays were 2,2-diphenyl-1-picryl-hydrazyl (DPPH)
free radical scavenging assay, hydroxyl radical scavenging assay, superoxide anion radical scavenging
assay and reducing capacity assessment. Amongst the seven plant peels, the acetone extract of
Mangifera indica was the most potent and in some cases even better than the standard. The results
obtained indicate that M. indica peel may become important as a cheap and noticeable natural source of
compounds with health protective potential, which can be used in pharmaceutical, nutraceutical and
food preparation.
Key words: Antioxidant activity, Mangifera indica, Lagenaria siceraria, peels, total phenol content, solvent
extracts.
INTRODUCTION
Free radicals have been shown to be harmful as they
react with important cellular components such as
proteins, DNA and cell membrane (Mantena et al., 2008).
The body on the other hand, requires free radicals for
immune system responses. However, an overload of
these molecules had been linked to certain chronic
diseases of heart, liver and some form of cancers
(Temple, 2000; Prakash et al., 2007). Human body
contains anti-free radical defense system, which includes
antioxidant enzymes like catalase, peroxidase and
superoxide dismutase and antioxidants like ascorbic acid
and tocopherol (Oke et al., 2009). An antioxidant (free
radical scavenger) is a compound that inhibits or delays
the oxidation of substrates even if the compound is
present in a significantly lower concentration than is the
oxidized substrate. These free radical scavenger help in
preventing stress induced diseases such as melanoma,
*Corresponding author. E-mail: svchanda@gmail.com.
cardiac disorders, diabetes mellitus, inflammatory and
neurodegenerative diseases, cancer (Prakash et al.,
2007; Jing et al., 2008). Vegetables are a good source of
dietary antioxidants, such as vitamin C, vitamin E and -
carotene. The antioxidative phytochemicals in grains,
vegetables, fruits and medicinal plants have received
increasing attention for their potential role in preventing
human diseases (Pallauf et al., 2008).
Phenolic and polyphenolic compounds constitute the
main class of natural antioxidants present in plants,
foods, and beverages. The researchers opinion is that
natural phenolic antioxidants are health-promoting
substances and that their antioxidant mechanisms and
their biological activity should be investigated at a
fundamental scientific level (Antolovivich, 2004).
Flavonoids are a group of polyphenolic compounds,
which are widely distributed through out the plant
kingdom. Flavonoids exhibit several biological effects
such as anti-inflammatory, anti-hepatotoxic and anti-ulcer
actions (Bors et al., 1990; Liu, 2003). They are potent
antioxidants and have free radical scavenging abilities.
The antioxidant constituents are present in all parts of
64 J. Med. Plant. Res.
the plant such as bark, stalks, leaves, fruits, roots,
flowers, pods, seeds, stems, latex, hull (Baravalia et al.,
2009; Kaneria et al., 2009; Rajaei et al., 2010; Golivand
et al., 2010). Recent research revealed that fruit peels
and seeds, such as grape seeds and peels (Negro et al.,
2003), pomegranate peel (Singh et al., 2002), wampee
peel (Prasad et al., 2010) and mango seed kernel
(Kabuki et al., 2000) may potentially possess antioxidant
properties.
The objectives of the present investigation is to
determine the antioxidant property of peels of different
fruits and vegetables, that are commonly available and
readily consumed in India, and to indicate which of them
can become a new source of natural antioxidants for
food, nutraceutical and pharmaceutical industries.
Therefore, in the present study, seven peels of fruits and
vegetables (Ananas comosus (Linnaeus) Merr.,
Mangifera indica L., Lagenaria siceraria (Molina) Standl.,
Luffa acutangula L. (Roxb.), Momordica charantia L.,
Moringa oleifera Lam., Solanum tuberosum L.) were
screened for their in vitro antioxidant potential.
MATERIALS AND METHODS
Reagents
The reagents used for the study are potassium ferricyanide, ferric
chloride, 2,2-diphenyl-1-picryl-hydrazyl (DPPH), gallic acid, sodium
carbonate, Folin-Ciocalteau’s phenol reagent, aluminium chloride,
potassium acetate, quercetin, nitro blue tetrazolium (NBT),
phenazine methosulphate (PMS), reduced nicotinamide adenine
dinucleotide (NADH), Tris Buffer, 2-deoxy-D-ribose,
ethylenediamine tetra acetic acid (EDTA), trichloroacetic acid
(TCA), thiobarbituric acid (TBA), hydrogen peroxide, acetone,
methanol, hexane, chloroform, obtained from Hi-media, Merck or
sigma. All reagents used were of analytical grade.
Plant material
The aforementioned seven fresh fruits and vegetables were
collected from Rajkot, Gujarat, India. The taxonomic identity of the
plants was confirmed by Dr. N. K. Thakrar, Department of
Biosciences, Saurashtra University, Rajkot, India. They were
thoroughly washed with water and then peels were separated,
washed again and dried under shade. The dried peels were
homogenized to fine powder and stored in air tight bottles which
were later used for solvent extraction. The ethnobotanical
information (Anjaria et al., 2002; Mahattanatawee et al., 2006;
Gouado et al., 2007) of the screened plants is given in Table 1.
Extraction method
The dried powder of peels was extracted individually by cold
percolation method (Parekh and Chanda, 2007) using different
organic solvents like hexane, chloroform, acetone and methanol. 10
g of dried powder was taken in 100 ml of hexane in a conical flask,
plugged with cotton wool and then kept on a rotary shaker at 120
rpm for 24 h. After 24 h, the extract was filtered with eight layers of
muslin cloth; centrifuged at 5000 rpm for 10 min. Supernatant was
collected and the solvent was evaporated. The residue was then
added to 100 ml of solvent (chloroform, acetone and methanol) in a
conical flask, plugged with cotton wool and then kept on a rotary
shaker at 120 rpm for 24 h. After 24 h, the extract was filtered with
eight layers of muslin cloth; centrifuged at 5000 rpm for 10 min, the
supernatant was collected and the solvents were evaporated and
the dry extract was stored at 4ºC in air tight bottles. The residues
were weighed to obtain the extraction yield.
Determination of total phenol content
The total phenol content was determined according to Folin-
Ciocalteu’s reagent method (Mc Donald et al., 2001). 0.5 ml of
extract and 0.1 ml (0.5 N) Folin-Ciocalteu’s reagent was mixed and
the mixture was incubated at room temperature for 15 min. Then
2.5 ml saturated sodium carbonate solution was added and further
incubated for 30 min. at room temperature and the absorbance was
measured at 760 nm. Gallic acid was used as a positive control
(Morsi et al., 2010). Total phenol values are expressed in terms of
gallic acid equivalent (mg g-1 of extracted compound).
Determination of flavonoid content
The flavonoid content was determined according to aluminium
chloride colorimetric method (Chang et al., 2002). The reaction
mixture consisting in a final volume of 3 ml, 1.0 ml of sample (1
mg/ml) 1.0ml methanol and 0.5 ml of (1.2%) aluminium chloride and
0.5 ml (120 mM) potassium acetate was incubated at room
temperature for 30 min. The absorbance of all the samples was
measured at 415 nm. Quercetin was used as positive control
(Ghasemi et al., 2009; Kaneria et al., 2009). Flavonoid content is
expressed in terms of Quercetin equivalent (mg g-1 of extracted
compound).
Antioxidant testing assays
DPPH free radical scavenging activity
The free radical scavenging activity was measured by using 2, 2-
diphenyl-1-picryl-hydrazyl (DPPH) by the modified method of
McCune and Johns (2002). The reaction mixture consisting of
DPPH in methanol (0.3 mM, 1 ml) 1 ml methanol and different
concentrations of the solvent extracts (1 ml) was incubated for 10
min in dark, after which the absorbance was measured at 517 nm.
Ascorbic acid was used as positive control (Blois, 1958).
Hydroxyl radical scavenging activity
The hydroxyl radical scavenging activity of different solvent extracts
of peels was measured by studying the competition between
deoxyribose and test compound for hydroxyl radical generated by
Fe3+-ascorbic acid-EDTA-H2O2 system (Fenton reaction) according
to the method of Kunchandy and Rao (1990). The reaction mixture
containing (1.0 ml), 100 l of 2-deoxy-D-ribose (28 mM in 20 mM
KH2PO4 -KOH buffer, pH 7.4), 500 l of the various solvent
extracts, 200 l EDTA (1.04 mM) and 200 M FeCl3 (1:1 v/v), 100
l 1.0 mM H2O2 and 100 l ascorbic acid (1.0 mM) was incubated at
37ºC for 1 h. 1.0 ml of thiobarbituric acid (1%) and 1.0 ml of
trichloroacetic acid (2.8%) were added and incubated at 100ºC for
20 min. After cooling, absorbance of pink color was measured at
532 nm, against a blank sample. Gallic acid was used as a positive
control (Kunchandy and Rao, 1990).
Superoxide anion radical scavenging activity
The superoxide anion radical scavenging activity was measured
according to a described procedure (Robak and Gryglewski, 1988).
Superoxide generated in phenazine methosulphate (PMS),
nicotinamide adenine dinucleotide reduced (NADH) oxidation and
assayed by nitroblue tetrazolium (NBT) reduction. The reaction
mixture consisted in a final volume of 3 ml, 0.5 ml Tris–HCl buffer
(16 mM, pH 8.0), containing 0.5 ml of NBT (0.3 mM), 0.5 ml NADH
(0.936 mM) solution and 1.0 ml of various concentrations of
different solvents extracts. The reaction was initiated by adding 0.5
ml PMS solution (0.12 mM) to the mixture. The reaction mixture
was incubated at 25°C for 5 min and the absorbance was
measured at 560 nm against a blank sample. Gallic acid was used
as a positive control (Robak and Gryglewski, 1988).
Reducing capacity assessment
The reducing capacity assessment of different solvent extracts of
peels was determined using the modified method of Athukorala et
al. (2006). 1 ml of different concentrations of solvent extracts was
mixed with phosphate buffer (2.5 ml, 200 mM, and pH 6.6) and
potassium ferricynide (2.5 ml, 30 mM). The mixture was then
incubated at 50ºC for 20 min. There after, trichloroacetic acid (2.5
ml, 600 mM) was added to the reaction mixture and then
centrifuged for 10 min at 3000 rpm. The upper layer of solution (2.5
ml) was mixed with distilled water (2.5 ml) and FeCl3 (0.5 ml, 6 mM)
and the absorbance was measured at 700 nm. Ascorbic acid was
used as positive control (Ksouri et al., 2009).
Statistical analysis
All experiments were repeated at least three times. Results were
reported as mean ± S.E.M. (standard error of mean).
RESULTS AND DISCUSSION
Extractive yield
The extractive yield of different screened fruit and
vegetable peels is given in Table 2. The extractive yield
varied among different fruit and vegetable peels and
among the solvents used. In all the plant peels, methanol
extract showed highest extractive yield than the other
extracts. In methanol extracts, it can be ranked from high
to low in the following order M. Oleifera (21.05) > L.
siceraria (19.69) > A. comosus (17.30) > M. indica
(15.82) > M. charantia (11.25) > S. tuberosum (10.17) >
L. acutangula (7.24). In acetone extracts, M. indica (5.64)
showed highest, while L. acutangula (0.96) showed
lowest extractive yield. In chloroform extract, M. charantia
(3.87) showed maximum extractive yield, while minimum
was in A. comosus (0.89). In hexane extract maximum
yield was in L. siceraria (3.8), and minimum in A.
comosus (0.89). There are many reports in the literature
where extractive yield varied with different solvents
(Vaghasiya and Chanda, 2007; Yang et al., 2007).
Extraction is critical to the recovery of antioxidant
phytochemicals; under the same time and temperature
conditions, the solvents used and the chemical property
of samples are the two most important factors (Shimada
et al., 1992).
Kalpna et al. 65
Total phenol and flavonoid content
Phenolic are the most wide spread secondary
metabolites in the plant kingdom. Flavonoids are through
scavenging or chelating process. Phenolic compounds
are a class of antioxidant agents, which act as a free
radical scavengers. It is believed that the phenolic and/or
polyphenolic compounds biosynthesized in the plant
sample might be responsible for antioxidant activity
(Kessler et al., 2003).
In the present work, seven vegetable and fruit peels in
various solvents were evaluated for their total phenol and
flavonoid content (Table 2). In all the plant peels, total
phenolic content was more than the flavonoid content.
The acetone extract had maximum amount of phenols
followed by methanol extract. The flavonoid content was
maximum in hexane extract.
Among seven plants tested, acetone extract of M.
indica contained high amount of phenol content while L.
siceraria (acetone) and M. oleifera (hexane) contained
high amount of flavonoid content. The results showed
that acetone was superior to methanol in selective
extraction of total phenols as also reported by Bensky et
al. (2004).
Antioxidant testing assays
Many methods have been proposed to evaluate the
antioxidant potential of natural sources of antioxidants.
However, the antioxidant capacity of plant extracts
cannot be evaluated by any one single assay because of
the complex nature of phytochemicals present in them,
solvent used for extraction and lastly the mechanism of
different antioxidant assays is different. Therefore, it is
essential that in order to assess the antioxidative
capacity of any plant, more than one solvent and more
than one antioxidant assays had to be performed (Singh
et al., 2007; Chanda and Dave, 2009; Chanda and
Nagani, 2010). In the present study, DPPH, superoxide
anion and hydroxyl radical scavenging activities and
reducing capacity assessment was evaluated in seven
fruit and vegetable peels extracted in hexane, chloroform,
acetone and methanol.
DPPH free radical scavenging activity
There are different methods for estimation of antioxidant
activity but the most widely used methods are those that
involve generation of free radical species which are then
neutralized by antioxidant compounds. DPPH radical is
commonly used as substrate to evaluate antioxidant
activity; it is a useful and stable free radical that can
accept an electron or hydrogen radical to become a
stable molecule. The reduction of DPPH free radical was
determined by the decrease in its absorbance at 517 nm
induced by different antioxidants. DPPH free radical
reacts with antioxidants, consequentially, absorbance
66 J. Med. Plant. Res.
Table 1. Ethnobotanical information of screened plants.
No. Botanical name Vernacular
name Family Medicinal/therapeutic use
1 M. indica L. Ambo Anacardiaceae Peel as a source of dietary fiber and antioxidant, The peel and pulp rich in
starch and pectins and source of antioxidants including ascorbic acid,
carotenoids and phenolic compounds
2
A. comosus
(Linnaeus) Merr.
Ananas
Bromeliaceae
Fruit, peel or juice is used in folk remedies for corns, tumors, and warts.
Reported to be abortifacient, depurative, cholagogue, diaphoretic, digestive,
emmenagogue, diuretic, hydragogue, discutient, estrogenic, intoxicant,
parasiticide, purgative, laxative, refrigerant, styptic, and vermifuge, Many
real or imagined pharmacological effects are attributed to bromelain: Burn
debridement, antiinflammatory action, smooth muscle relaxation and
stimulation of muscle contractions, cancer prevention and remission, ulcer
prevention, appetite inhibition, enhanced fat excretion, and sinusitis relief
3
L. siceraria
(Molina) Standl.
Dudhi
Cucurbitaceae
Fruits are used for cardio protective, cardio tonic, diuretic, antihepatotoxic
activity, purgative and cooling effects. It also cures pain, ulcers, fever, and
other bronchial disorders
4
S. tuberosum L.
Batata
Solanaceae
Peels are used in India to treat swollen gums and to heal burns and helpful
in the treatment of peptic ulcers, bringing relief from pain
5
L. acutangula
(L.) Roxb.
Turiya
Cucurbitaceae
Fruits: Diuretic, tonic, nutritive. Leaves used in splenitis, hemorrhoids, ring
worm, leprosy, granular conjunctivitis
6
M. charantia L.
Karela
Cucurbitaceae
Fruits: Bitter, thermogenic, acrid, stimulant, purgative, antidiabetic,
digestive, anti-inflammatory, hydrophobia, malarial
7
M. oleifera Lam.
Mitho
Saragvo
Moringaceae
anti-inflammatory, rich in vitamin A and C, anodyne, anthelminthic,
ophthalmic
decreases and the DPPH free radical is converted into
the DPPP-H form. The degree of discoloration indicates
the scavenging potential of antioxidant compounds of
extracts in terms of H2 donating ability. Concentration of
sample at which the inhibition percentage reaches 50% is
its IC50 value. IC50 values are negatively related to the
antioxidant activity, as it express the amount of
antioxidant needed to decrease its radical concentration
by 50%. The lower IC50 value represents the higher
antioxidant activity of the tested sample.
In the present work, seven plant species, extracted
using various solvents were evaluated for their
scavenging activity. Out of 28 extracts investigated, 19
extracts showed IC50 value more than 1000 µg/ml (Table
3), the remaining 9 plant extracts showed a varied level
of DPPH scavenging activity. IC50 values ranged from
16.5 to 790 µg/ml (Table 3). Ascorbic acid was used as
standard and its IC50 value was 11.4 µg/ml.
The hexane extracts of all the studied plants showed
low DPPH free radical scavenging activity (>1000 µg/ml)
as compared to other solvent extracts. It appears that the
free medical scavenging compounds are in polar
solvents.
The IC50 value of chloroform extract of M. indica was
140 g/ml (Table 3). The acetone and methanol extracts
of M. indica peels showed very good DPPH free radical
scavenging activity, which were almost near to that of
standard ascorbic acid (Table 3). The IC50 values of
acetone and methanol extracts of M. indica were 16.5
and 23.5 g/ml, respectively (Table 3). The radical
scavenging activity of M. indica peel could be related to
the phenolics present in them, thus contributing to their
electron transfer/ hydrogen donating ability. Saravana
Kumar et al. (2008) reported similar results.
In nonpolar solvents, chloroform extract showed
moderate activity, while hexane extract did not show any
activity at all. Therefore, it can be concluded that
extracting solvents play an important role in expressing
antioxidant activity.
The polar solvents appear to be better than non-polar
solvents; based on the present results, the polar solvent
acetone appears to be the best.
Hydroxyl radical scavenging activity
The hydroxyl radical is an extremely reactive free radical
formed in biological systems and had been implicated as
a highly damaging species in free radical pathology,
Kalpna et al. 67
Table 2. Extractive yield (%) and total phenol and flavonoid contents of different peels in different solvent extracts.
No. Plant species Extract % yield (w/w)# Total phenol
content (mg/g)*
Flavonoid
content (mg/g)*
Hexane 0.56 1.87 ± 0.23 19.00 ± 0.22
Chloroform 0.89 12.02 ± 1.39 25.50 ± 1.25
Acetone 2.13 10.34 ± 0.77 4.25 ± 0.60
1 A. comosus
Methanol 17.3 18.66 ± 0.30 3.19 ± 0.23
Hexane
2.4
1.53 ± 0.16
26.29 ± 0.82
Chloroform 2.24 53.58 ± 1.17 10.24 ± 0.42
Acetone 5.64 490.64 ± 0.43 11.25 ± 0.20
2 M. indica
Methanol 15.82 216.74 ± 0.30 4.83 ± 0.08
Hexane
3.80
2.78 ± 0.29
8.37 ± 0.67
Chloroform 1.38 30.13 ± 0.74 14.69 ± 0.14
Acetone 4.09 304.44 ± 12.01 36.08 ± 0.50
3
L. siceraria
Methanol 19.69 144.11 ± 2.55 22.10 ± 0.27
Hexane
0.69
3.11 ± 0.40
13.30 ± 0.65
Chloroform 1.32 10.32 ± 0.32 2.47 ± 0.99
Acetone 0.96 19.39 ± 0.57 8.02 ± 3.97
4
L. acutangula
Methanol 7.25 28.10 ± 0.30 4.25 ± 0.20
Hexane
0.69
5.37 ± 0.03
2.71 ± 1.10
Chloroform 3.87 5.50 ± 0.15 6.21 ± 0.47
Acetone 2.30 5.44 ± 0.44 7.15 ± 1.36
5
M. charantia
Methanol 11.25 8.22 ± 0.21 2.75 ± 0.24
Hexane
1.29
1.05 ± 0.09
11.54 ± 1.01
Chloroform 2.06 7.34 ± 0.23 10.32 ± 0.17
Acetone 0.97 29.94 ± 0.85 31.90 ± 4.06
6
M. oleifera
Methanol 21.05 16.87 ± 0.03 7.91 ± 0.18
Hexane
2.28
4.45 ± 0.28
2.20 ± 0.23
Chloroform 2.39 9.60 ± 0.51 8.93 ± 0.41
Acetone 1.34 47.79 ± 0.71 12.61 ± 0.54
7
S. tuberosum
Methanol 10.17 46.94 ± 0.34 5.78 ± 0.17
# The values are mean (n = 3); * The values are mean ± standard error mean (n = 3).
capable of damaging almost every molecules found in
living cells (Hochestein and Atallah, 1988). The most
reactive free radical is the hydroxyl radical which is
known to initiate lipid peroxidation and cause
fragmentation of DNA leading to mutation. The
chloroform extract of all the studied plants showed poor
hydroxyl radical scavenging activity (>1000 µg/ml, Table
3), therefore only the results of acetone and methanol
extracts is presented in the present work. Gallic acid was
used as standard (140 µg/ml). Best hydroxyl radical
scavenging activity was shown by acetone extract of M.
indica; its IC50 value was 350 µg/ml.
Superoxide anion radical scavenging activity
Superoxide anion radical is a weak oxidant but it gives
rise to the generation of powerful and dangerous hydroxyl
radicals as well as singlet oxygen, both of which
contribute to the oxidative stress. Superoxide anion,
which is a reduced form of molecular oxygen, had been
implicated in the containing oxidation reactions
associated with aging (Cotelle et al., 1996). Antioxidant
properties of flavonoid are effective mainly via the
scavenging of superoxide anion radical. In the
PMS/NADH-NBT system, superoxide anion derived from
68 J. Med. Plant. Res.
Table 3. DPPH free radical, hydroxyl radical and superoxide anion radical scavenging activities of different solvent extracts of
screened plants.
IC50 value (g/ml)
DPPH OH SO
No. Plant name
HE CH AC ME HE CH AC ME HE CH AC ME
1 Ananas comosus A A A A ND A 700 A ND A A A
2 Mangifera indica A 140 16.5 23.5 ND A 350 A ND A 86 187.5
3 Lagenaria siceraria A 790 58 160 ND A 335 660 ND A 750 A
4 Solanum tuberosum A A 200 380 ND A 910 A ND A A A
5 Luffa acutangula A A A A ND A A A ND A A A
6 Momordica charantia A A A A ND A A 750 ND A A A
7 Moringa oleifera A A 520 A ND A A A ND A A A
DPPH: 2,2-diphenyl-1-picryl-hydrazyl free radical; OH: hydroxyl radical; SO: superoxide anion radical; A: >1000; ND: not done; HE: hexane
extract; CH: chloroform extract; AC: acetone extract; ME: methanol extract.
dissolved oxygen by PMS/NADH coupling reaction
reduces NBT. Antioxidants are able to inhibit the blue
NBT formation (Cos et al., 1998). The decrease of
absorbance at 560 nm with antioxidants thus indicates
the consumption of superoxide anion radical in the
reaction mixture. Table 3 shows the IC50 values of
superoxide anion radical scavenging activity.
The chloroform extract of all the studied plants showed
poor superoxide anion radical scavenging activity (>1000
µg/ml, Table 3). The IC50 value of acetone extract of M.
indica peel was 86 µg/ml while that of methanol extract
was 187.5 µg/ml. The acetone extract appears to be a
better scavenger than the standard gallic acid (IC50 = 185
µg/ml) and methanol extract is as good as that of the
standard.
Reducing capacity assessment
The reducing capacity assessment of a compound may
serve as a significant indicator of its potential antioxidant
activity. Many reports have revealed that there is a direct
correlation between antioxidant activity and reducing
capacity assessment of components of medicinal herbs
(Yildirim et al., 2001). Therefore reducing capacity
assessment may be used as an indicator of potential
antioxidant activity. In this method, antioxidant
compounds form a colored complex with potassium
ferricynide, trichloroacetic acid and ferric chloride that is
measured at 700 nm. Increase in absorbance of the
reaction mixture indicates the increase in the reducing
capacity assessment of the sample. Ascorbic acid was
used as a standard (Ksouri et al., 2009).
In the present work, seven vegetable and fruit peels in
various solvents were evaluated for their reducing
capacity assessment (Figures 1 to 2). Out of seven
studied vegetable and fruit peels, M. indica (Figure 1a), L.
siceraria (Figure 1b) and L. acutangula (Figure 2b) peels
showed reducing capacity assessment, while other peel
extracts showed poor reducing capacity.
In M. indica, there was concentration dependent increase
in the absorbance of reaction mixture for all the three
extracts and standard ascorbic acid (Figure 1a). The
acetone extract showed maximum absorbance and
hence maximum capacity assessment among its various
solvent extracts. In fact, the reducing capacity
assessment of acetone extract was more than that of the
standard ascorbic acid (Figure 1a).
The reducing capacity assessments of other extracts
were in the order: acetone extract > ascorbic acid >
methanol extract > chloroform extract. The ability of M.
indica peel to exhibit significant reducing capacity
assessment and to scavenge DPPH radicals suggests
that it is an electron donor and can react with free
radicals to convert them to more stable products and
terminate radical chain reaction.
Plant extracts and plant-derived antioxidants can elicit
a number of in vivo effects such as promotion of
increased synthesis of endogenous antioxidant defenses
or themselves acting directly as antioxidants (Halliwell,
1990). However, antioxidant activity of a compound can
also be assessed in vitro by testing it on biologically
relevant reactive oxygen species. The ability of M. indica
peel to exhibit significant reducing capacity assessment
and to scavenge DPPH radicals suggests that it is an
electron donor and can react with free radicals to convert
them to more stable products and terminate radical chain
reaction.
Conclusion
In this study, several in vitro assays were applied to
evaluate the antioxidant potential of seven fruits and
vegetables peels. The results of the present study would
certainly help to ascertain the potency of the crude
extract of peels of M. indica as a potential source of
natural antioxidants. The author think they are the first to
report about the strong antioxidant capacity of acetone
extract of M. indica peel. However, further studies are
Kalpna et al. 69
M. indica
0.0
0.5
1.0
1.5
2.0
20 40 60 80 100 120 140 160 180
Concentration (ug)
Chloroform Acetone Methanol Ascorbic acid
L. siceraria
0.0
0.5
1.0
1.5
2.0
20 40 60 80 100 120 140 160 180
Concentration (ug)
Ab so rbance ( 700nm)
Chloroform Acetone Methanol Ascorbic acid
S. tuberosum
0.0
0.5
1.0
1.5
2.0
20 40 60 80 100 120 140 160 180
Concentration (ug)
Abso rba nce ( 700nm )
Chloroform Acetone Methanol Ascorbic acid
c
b
a
Figure 1. Reducing capacity assessment of different solvents
extracts.
70 J. Med. Plant. Res.
A. comosus
0.0
0.5
1.0
1.5
2.0
20 40 60 80 100 120 140 160 180
Concentration (ug)
A b so rb a n ce ( 70 0 n m)
Chloroform Acetone Methanol Ascorbic acid
L. acutangula
0.0
0.5
1.0
1.5
2.0
20 40 60 80 100 120 140 160 180
Concentration (ug)
A b so rb a nce ( 70 0 n m )
Chloroform Acetone Methanol Ascorbic acid
a b
M. charantia
0.0
0.5
1.0
1.5
2.0
20 40 60 80 100 120 140 160 180
Concentration (ug)
A b so rb a n ce ( 70 0 n m )
Chloroform Acetone Methanol Ascorbic acid
c
M. oleifera
0.0
0.5
1.0
1.5
2.0
20 40 60 80 100 120 140 160 180
Concentration (ug)
A b so rb a n ce ( 70 0 n m )
Chloroform Acetone Methanol Ascorbic acid
d
Figure 2. Reducing capacity assessment of different solvents extracts.
required before it can be used as a source of antioxidant.
These are novel, natural and economic sources of
antioxidants, which can be used in the prevention of
diseases caused by free radicals. Therefore, our study
will definitely open, scope for future utilization of these
waste products for therapeutic purpose. Our results also
indicate that selective extraction from natural materials,
by an appropriate solvent, is important for obtaining
fractions with high antioxidant activity. The acetone
extract of M. indica peel showed best antioxidant capacity
may be because of its higher phenolic content which
normally is the major determinant of antioxidant potential
of food plants. Therefore, M. indica peel can be a good
source of natural antioxidants.
ACKNOWLEDGMENTS
The authors thank Prof. S. P. Singh, Head, Department
of Biosciences, Saurashtra University, Rajkot, Gujarat,
India for providing excellent research facilities. One of the
authors, Mital Kaneria is thankful to University Grants
Commission, New Delhi, India for providing financial
support (Junior Research Fellowship).
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... The DPPH is widely used and is a common technique for evaluating the free radical removal activity of different plant extracts, DPPH is a stable free radical soluble in ethanol or methanol and the reduction of free radicals is determined by the decrease in absorbance at 715nm when the color of the DPPH test solution changes from purple to light yellow. (Kalpna et al. 2011) and return it to DPPH-H by means of antioxidants that give it an electron or a proton, thus removing free radicals (Brand et al., 1995). Figure (3-3) shows the ability of alcoholic extracts of citrus peels to bind the ferrous ion and compare it with citric acid. ...
... Table showed that the inhibitory acitivity of alcoholic extracts of citrus peels (lemon, grapefruit and mandarin) was close to all types of bacteria studied, and the results of the same table showed that with an increase in the concentration of the extract, the inhibitory ability of all types of peels studied increased. The inhibition diameter of the alcoholic extract of lemon peels at the concentration of 50mg/ml towards E-coil, Klebseilla spp, and Staphylococcus aurus was (13,14,15) mm, respectively and the diameter of the inhibition increased by increasing the concentration of the extract to 200 mg/ml, where the diameter of the inhibition reached (18,15,19) mm, respectively. As for the alcoholic extract of grapefruit peels, the inhibition diameter at the concentration of 50mg/ml towards E-coil, Klebseilla spp, and Staphylococcus aurus was (13,12,14) mm, respectively and the diameter of the inhibition was increased by increasing the concentration of the extract to 200 mg/ml, where the diameter of the inhibition reached (15,16,15) mm, respectively. ...
... Table showed that the inhibitory acitivity of alcoholic extracts of citrus peels (lemon, grapefruit and mandarin) was close to all types of bacteria studied, and the results of the same table showed that with an increase in the concentration of the extract, the inhibitory ability of all types of peels studied increased. The inhibition diameter of the alcoholic extract of lemon peels at the concentration of 50mg/ml towards E-coil, Klebseilla spp, and Staphylococcus aurus was (13,14,15) mm, respectively and the diameter of the inhibition increased by increasing the concentration of the extract to 200 mg/ml, where the diameter of the inhibition reached (18,15,19) mm, respectively. As for the alcoholic extract of grapefruit peels, the inhibition diameter at the concentration of 50mg/ml towards E-coil, Klebseilla spp, and Staphylococcus aurus was (13,12,14) mm, respectively and the diameter of the inhibition was increased by increasing the concentration of the extract to 200 mg/ml, where the diameter of the inhibition reached (15,16,15) mm, respectively. ...
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The current study included the alcoholic extraction of peels of some types of citrus fruits, which included lemons, grapefruit, and Mandarin, and studying their ability as natural antioxidants, by estimating the amount of phenols and flavonoids, and the antioxidant activity, in addition to studying the inhibitory activity of the studied alcoholic extracts. The results of the study indicated the superiority of the amount of phenols in the alcoholic extract of mandarin, which amounted to 272 mg/ml, followed by lemon peel extract of 245 mg/ml, while grapefruit recorded the lowest amount, which amounted to 238 mg/ml. As for the results of the amount of flavonoids in the alcoholic extract of lemon peel, it was the highest, reaching 41.73mg/ml followed by the extract of mandarin peels 21.44 mg/ml, and finally the alcoholic extract of grapefruit peels 20.1 mg/ml. As for the results of the antioxidant activity of the studied peels, represented by measuring DPPH, the results indicated that the extract of grapefruit peels had the highest antioxidant activity, reaching (16.35 µg equivalent ascorbic acid/ml) at a concentration of 25 mg/ml, followed by lemon peels, where the DPPH value reached (8.51 µg equivalent ascorbic acid/ ml).) and then mandarin peels (6.49 µg equivalent to ascorbic acid/ ml) at the same concentration. As for the ability to bind ferrous ion, the mandarin peel extract recorded the highest binding rate, which reached (84.58%), followed by lemon peels (78.78%), and then grapefruit peels (76.18%), While lemon peel extract recorded the highest ability to Scavenging hydrogen peroxide, which reached (77.1%), followed by grapefruit peels, which amounted to (50.01%), while the mandarin peel extract recorded the lowest percentage (36.24%). As for the results of the reducing power, the extract of mandarin peels was the highest, as it reached (1.453nm), followed by the extract of grapefruit peels (1.177nm) and finally lemon peels (0.507nm). The results of the inhibitory ability of the alcoholic extracts of the citrus peels studied indicated that all the extracts possessed an inhibitory activity against E coil, Klebsella spp, and Staphylococcus aurus in different concentrations, where the inhibitory ability increased with the increase in the concentration of the extract used.
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... There are many references in the literature about antioxidant activity by DPPH method (Pari et al., 2007;Santos et al., 2012;Charoensin, 2014). Kalpna et al. (2011) reported antioxidant activity against superoxide and hydroxyl radicals in chloroform, acetone and methanol extracts (IC50 value μg mL -1 >1000). Fejeŕ et al. (2019) found high antioxidant activity of crushed leaf ethanol extracts against superoxide radical (83.6%, resp. ...
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