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Chemical Composition, Nutritional Values and Antibacterial Activities of Watermelon Seed (Citrullus lanatus)

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The World Health Organization (WHO) defines traditional medicine as the sum total of the knowledge, skills, and practices based on the theories, beliefs and experiences indigenous to different cultures, whether explicable or not, used in the maintenance of health as well as in the prevention, diagnosis, improvement or treatment of physical and mental illness. Plants are traditionally used for treatment of bacterial infections. The aim of this study was to investigate chemical composition, nutritional evaluation and antibacterial activities of watermelon seeds. The qualitative phytochemical analysis of watermelon indicated that alkaloids were moderately present, tannins, saponins, flavonoids, and phenols were all present. The quantitative analysis of watermelon indicated 3.080 mg/g for alkaloids, 0.304mg/g for phenols, 0.117 mg/g for tannins, 0.200mg/g for saponins and 2.675 mg/g for flavonoids. The vitamin composition of watermelon seeds indicated 0.03 mg/100 g for vitaminB1, 0.01 vitaminB2, 0.64 mg/100g for vitaminB3, 0.24 mg /100 g vitaminB6 and 0.01 for vitaminB12.The bioactivities of extract were tested, against Proteus mirabilis, Bacillus cereus, Staphylococcus aureus, Escherichia coli, Necropsobacter rosorum, Tsukamurella hongkongensis, Lactobacillus sp, Staphylococcus petrasii, Neisseria sicca, Dietzi amaris, Pseudomonas oryzyhabitans, Klebsiella pneumoniae, Advenella incenata, Neiserria subflava and Serriatia marcescens. Researchers are advised to turn their attention towards plants products, which is most promising area in search of new biologically activity compounds with better activity against multi drug resistant strains and reduced antibiotic related side effects. Keywords: Seeds watermelon antimicrobial activity extract.
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*Corresponding author: E-mail: oyesolakemi@gmail.com;
International Journal of Biochemistry Research & Review
27(1): 1-9, 2019; Article no.IJBCRR.46989
ISSN: 2231-086X, NLM ID: 101654445
Chemical Composition, Nutritional Values and
Antibacterial Activities of Watermelon Seed
(Citrullus lanatus)
Asoso Oluwakemi Sola
1*
, Ogunmefun Olayinka Temitayo
1
, Adelegan Olufunke
2
and Farida Shittu
1
1
Department of Biological Sciences, College of Sciences, Afe Babalola University, Ado-Ekiti,
Ekiti State, Nigeria.
2
Department of Medical Microbiology and Parasitology, College of Medicine and Health Sciences,
Afe Babalola University, Ado-Ekiti, Ekiti State, Nigeria.
Authors’ contributions
This work was carried out in collaboration among all authors. Author AOS designed the study,
performed the statistical analysis, wrote the protocol and wrote the first draft of the manuscript.
Authros OOT and AO managed the analyses of the study. Author AOS managed the literature
searches. All authors read and approved the final manuscript.
Article Information
DOI: 10.9734/IJBCRR/2019/v27i130113
Editor(s):
(1) Dr. Noureddine Benkeblia, Professor, Department of Life Sciences, The University of the West Indies, Jamaica.
Reviewers:
(1) Luana Fernandes, Centro de Investigação de Montanha, Escola Superior Agrária de Coimbra, Instituto Politécnico de
Bragança, Portugal.
(2)
Dingwoke, Emeka John, Ahmadu Bello University, Zaria, Nigeria.
(3)
Oshim, Ifeanyi Onyema, Nnamdi Azikiwe University, Nigeria.
Complete Peer review History:
http://www.sdiarticle3.com/review-history/46989
Received 24 March 2019
Accepted 28 May 2019
Published 24 August 2019
ABSTRACT
The World Health Organization (WHO) defines traditional medicine as the sum total of the
knowledge, skills, and practices based on the theories, beliefs and experiences indigenous to
different cultures, whether explicable or not, used in the maintenance of health as well as in the
prevention, diagnosis, improvement or treatment of physical and mental illness. Plants are
traditionally used for treatment of bacterial infections. The aim of this study was to investigate
chemical composition, nutritional evaluation and antibacterial activities of watermelon seeds. The
qualitative phytochemical analysis of watermelon indicated that alkaloids were moderately present,
tannins, saponins, flavonoids, and phenols were all present. The quantitative analysis of
Original Research Article
Sola et al.; IJBCRR, 27(1): 1-9, 2019; Article no.IJBCRR.46989
2
watermelon indicated 3.080 mg/g for alkaloids, 0.304mg/g for phenols, 0.117 mg/g for tannins,
0.200mg/g for saponins and 2.675 mg/g for flavonoids. The vitamin composition of watermelon
seeds indicated 0.03 mg/100 g for vitaminB
1
, 0.01 vitaminB
2
, 0.64 mg/100g for vitaminB
3,
0.24 mg
/100 g vitaminB
6
and 0.01 for vitaminB
12
.The bioactivities of extract were tested, against Proteus
mirabilis, Bacillus cereus, Staphylococcus aureus, Escherichia coli, Necropsobacter rosorum,
Tsukamurella hongkongensis, Lactobacillus sp, Staphylococcus petrasii, Neisseria sicca, Dietzi
amaris, Pseudomonas oryzyhabitans, Klebsiella pneumoniae, Advenella incenata, Neiserria
subflava and Serriatia marcescens. Researchers are advised to turn their attention towards plants
products, which is most promising area in search of new biologically activity compounds with better
activity against multi drug resistant strains and reduced antibiotic related side effects.
Keywords: Seeds; watermelon; antimicrobial activity; extract.
1. INTRODUCTION
Many plant extracts have been shown to
possess antimicrobial properties active against
microorganisms in-vitro. Watermelon is a large
annual plant with long, weak, trailing or climbing
stems which are five-angled (five-sided) and up
to 3 m (10 ft) long. The Watermelon is a
flowering plant thought to have originated in
Southern Africa, where it is found growing wild. It
reaches maximum genetic diversity there, with
sweet, bland and bitter forms. In the 19
th
century,
Alphonse de Candolle considered the
watermelon to be indigenous to tropical Africa
[1]. Citrullus colocynthis is often considered to
be a wild ancestor of the watermelon and is now
found native in north and West Africa. However,
it has been suggested on the basis of
chloroplast DNA investigations that the
cultivated and wild watermelon diverged
independently from a common ancestor,
possibly C. ecirrhosus from Namibia. Evidence
of its cultivation in the Nile Valley has been
found from the second millennium BC onward.
Watermelon seeds have been found at Twelfth
Dynasty sites and in the tomb of Pharaoh
Tutankhamun [2].
Watermelon seeds are easily available during
summer season. Though it is not an oilseed but
many researchers have reported that C. vulgaris
seed kernels contain about 52.6% oil, so these
are a good source of energy (628k.cal).
2. MATERIALS AND METHODS
2.1 Sample Collection
Watermelon (Citrullus lanatus) seeds used for
this study were obtained fresh from retailed fruit
sellers from Oja-Oba Market, Ado Ekiti, Ekiti
State.
2.2 Preparation of Extract
The extraction of W atermelon was achieved
using a rotary evaporator (RE -52 A Union
Laboratories, England), was carried out
separately using methanol as solvent. The
Watermelon was also washed and cut into slices
to remove the seeds and it was also air dried for
30 days. W atermelon seeds were ground to fine
powder separately, with the use of an electric
blender (Thomas Wiley machine, model 5 USA).
The sample was weighed (100 g) and soaked in
400 ml of methanol separately in a conical flask.
The mixture in the flasks was kept at room
temperature for 24 hours with intermittent
agitation and the sample was filtered into a
beaker. The filtrate of the sample was
concentrated to dryness by evaporation at 45ºC
in a water bath for 3 days.
2.3 Proximate Analysis of the Plant
Extracts
2.3.1 Moisture content
A clean and well labeled dish was weighed and
oven dried (W
1
), enough sample of the plant
parts were added into the dish and weighed
(W
2
), the dish was transferred and with the
content to the thermo setting oven at about
105ºC for about 24 hours. The dish was moved
from oven to desiccators and was allowed to cool
for about one hour and weighed. Step 4 was
repeated to get constant W
3
.
% Moisture = (Loss in weight / Weight of
sample before drying) x 100
= (W
2
– W
3
/
W
2
– W
1
)
× 100
% Total solid or % dry matter = (W
3
– W
1
/
W
2
W
1
)
X 100
Sola et al.; IJBCRR, 27(1): 1-9, 2019; Article no.IJBCRR.46989
3
W
1
= weight of empty dish
W
2
= weight of dish + sample
W
3
= weight of dish + dried sample
2.3.2 Ash content
Silica dish or crucible was placed in muffle
furnace for about 15 minutes at 350°C, it was
removed and cooled in a desiccator for about
one hour, the crucible was weighed as (W1),
enough sample was added into the crucible (0.5
2 g) and content was weighed as (W
2
), then
the crucible was placed inside the muffle furnace
and slowly increase the temperature from 200ºC
– 450ºC to avoid incomplete ashing. The sample
was ashed until it become whitish in colour. Later
it was removed and cooled to moisten with few
drops of distilled water and dried on water bath
which was returned to the furnace. The furnaces
were removed to desiccator and allow cooling to
room temperature. The crucible and the content
were reweighed as (W
3
).
Calculation:
% Ash = (W
3
– W
1
/ W
2
– W
1
) X 100
% organic matter = 100 - % Ash.
2.3.3 Protein content
There are 3 stages involved in the process.
Digestion:
Digestion converts nitrogen in food to ammonia.
About lg of the sample was weighed into kjedahl
flasks in duplicate, L – Tyrosine were weighed
into another kjedahl flask as blank for standard.
Copper sulfate and potassium sulphate mixed in
ratio 10:150 was added as catalyst to the
samples. (CuS0
4
– 5H
2
0 and K
2
S0
4
). Little anti
bombing granules was added to the mixtures to
prevent bombing of the flask by the acid and
10mls of concentrated H
2
SO
4
acid was added to
digest the samples and the digestion flasks were
placed into the digester at 400
0
c for some time
until the samples were clear.
Distillation:
NaOH converts Ammonium sulphate into
Ammonia gas
(NH
3
)
2
SO
4
+2NaOH------->2NH
3
+2H
2
O
+Na
2
SO
4
The low PH of boric acid converts Ammonia gas
to Ammonium ion and boric to borate ion.
NH
3
+H
3
BO
3
---------->NH
4
+H
2
BO
3
-
Fifteen mls of Boric acid (H
3
BO
3
) was placed in a
200 ml conical flask to serve as the receiving
flask, to trap the ammonia vapor from the digest
and 2 drops of mixed indicator (methylene +
methyl red) was added to the boric acid. Ten mls
of digested sample was added to 10 ml of distil
water into a digestion flask. The conical flask and
the kjeldahi flask was placed into the
Nitrogen/protein determinator, NaOH was added
to the kjeldahi flask till color changed. The
sample was steamed and distilled into the
conical flask.
Titration:
The distillate was titrated with an acid of known
concentration e.g. 0.05MHcl.
Calculation:
% Nitrogen = (V
2
-V
1
) × C × 0.0140 × V ×
100/ W × V
1
V
1
– Volume of blank, V
2
–Volume of sample, C -
Concentration of acid, V -Total Volume of
digested Solution (ml),W -Weight of sample, V
1
-
Volume of distillation (ml).
Crude protein = % Nitrogen × Conversion
factor.
2.3.4 Crude fibre
Two grams of the dried sample was weighed and
placed in the flask, 200 ml of boiling sulphuric
acid solution was added. The extraction was
boiled with petroleum ether for 1hour with 200 ml
of 1.25% of sodium hydroxide solution and was
filtered through a filter paper and washed with
distilled water. The residue was transferred into a
crucible and oven dried at 105ºC, cooled in a
desicator and weighed as W
2
. The crucible were
placed in a muffle furnace at about 500ºC for
about 30 minutes and cooled inside a desiccator
and weighed as W
3.
% of crude fiber = (W
3
–W
1
/
W
2
- W
1
) × 100
Where
W
1
= weight of empty crucible
Sola et al.; IJBCRR, 27(1): 1-9, 2019; Article no.IJBCRR.46989
4
W
2
= weight of the crucible and the feed sample
W
3
= weight of the crucible and ashed sample
2.3.5 Crude fat
Two grams of the sample was weighed into 100
ml beaker and 2 ml of ethanol was added to fill
the round bottom flask up to 2/3 of the mark with
petroleum ether. The soxhlet extractor was fixed
up with a reflux condenser and was heated with
heating mantle at temperature of 40-60ºC for 1
hour and remove. Then it was extracted with 30
ml of diethylether to remove the solvent by
evaporating on a water bath and later transferred
to the beaker, the residue was placed inside the
oven and dried for about 1hour.
Weighed the residue as fat:
Calculation for fat content
% of fat = (Weight of the residue/ Weight of
the sample) × 100
2.4 Phytochemical Analysis
Phytochemical analysis of the extracts were
carried out qualitatively using accepted
laboratory techniques as described by
Nagalingam et al. [3]. Tests on the presence of
alkaloid, flavonoids, glycosides, saponins and
tannin were conducted accordingly.
2.5 Qualitative Analysis
2.5.1 Test for alkaloids
Five grams of each plant extracts were mixed
with 5 ml of 1% (v/v) aqueous hydrochloric acid
on a steam bath. One millilitre of the filtrate was
treated with few drops of Draggendoff’s reagent.
Blue-black turbidity serves as preliminary
evidence of alkaloids presence.
2.5.2 Test for saponins
Five grams of each plant extracts was shaken
with distilled water (5 ml) in a test tube. Frothing
which persists on warming was taken as
preliminary evidence of the presence of
saponins.
2.5.3 Test for tannins
Five grams of each plant extracts was added to
100 ml distilled water, stirred and filtered through
Whatman No 1 filter paper. Ferric chloride
reagent was added to the filtrate. A blue-black or
blue green precipitate determines the presence
of Tannins [4].
2.5.4 Test for flavonoids
Presence of flavonoids in the plant extracts was
tested by FeCl
3
and lead ethanoate solutions. A
green-blue or violet coloration on addition of
FeCl
3
solution and appearance of buffcoloured
precipitate on addition of lead ethanoate solution
indicated the presence of flavonoids in the
extract [5].
2.5.5 Test for phenols
One millilitre of each plant extract was mixed with
4 drops of ethanol 100% (v/v) and 3 drops of 1%
ferric chloride solution in test tube. Formation of
green or red-brown indicates the presence of
phenols.
2.6 Quantitative Analysis
2.6.1 Determination of tannins
Fine powdered ground plant sample (0.2 g) was
weighed into a 500 ml sample bottle. Then, 100
ml of 70% (v/v) aqueous acetone was added and
properly covered with a stopper. The bottles
were kept in water bath with shaker and shaken
for 2 hours at 30ºC. Each solution was then
centrifuged at 1600 rpm for 5 minutes and the
sediment was stored on ice. Each solution 0.2
ml) was pipetted into test tube and 0.8 ml of
distilled water was added. Standard tannic acid
solutions were prepared from a 0.5 mg/ml of the
stock and the solution was made up to 1 ml with
distilled water. Folin-ciocateau reagent (0.5 ml)
was added to both the sample and the standard
tannic acid solution followed by the addition of
2.5 ml of 20% (v/v) Na
2
CO
3.
The solutions were
then shaken vigorously and allowed to incubate
for 40 minutes at room temperature 28 + 2ºC.
The absorbance was read at 725 nm against a
standard tannic acid curve.
2.6.2 Determination of saponin concentration
Spectrophotometric method of [6] was used. Two
grams of each plant extract were weighed into a
250 ml beaker and 100 ml of Isobutyl alcohol
(100% v/v) was added. The mixture was shaken
in a shaker water bath for 5 hours to ensure
homogeneous mixture. The mixture was filtered
through No 1 Whatman filter paper into 100 ml
beaker containing 20 ml of 40% (v/v) saturated
Sola et al.; IJBCRR, 27(1): 1-9, 2019; Article no.IJBCRR.46989
5
solution of magnesium carbonate (MgCO
3
). The
mixture obtained was again filtered with No 1
Whatman filter paper to obtain a clean colourless
solution. One millilitre of the colourless solution
was pipetted into 50 ml volumetric flask and 2 ml
of 5% ferric chloride (FeCl
3
) solution was added.
The mixed solution was made up to the mark of
50 ml with distilled water. It was allowed to stand
for 30 minutes for colour (light brown)
development. The absorbance was read against
blank at 380 nm.
2.6.3 Determination of the amount of
alkaloids
Five grams plant extract was weighed into a 250
ml beaker and 200 ml of 10% (v/v) acetic acid in
200 ml of 100% (v/v) ethanol was added and
allowed to stand for 4 minutes. It was filtered
through Whatman’s No. 1 filter paper and the
extract was concentrated on a water bath (50ºC)
for 4 hours to one quarter of the original volume.
A solute ammonium hydroxide (10 ml) was
added drop wise to the extract until the
precipitation was completed. The whole solution
was allowed to settle and the precipitate was
collected and washed with dilute (2 M)
ammonium hydroxide and then filtered. The
residue was then considered as alkaloid which
was dried and weighed [7]. The formula written
below was used to calculate concentration of
alkaloid in percentage
Alkaloid (%) = (W
3
– W
2
/ W
1
) x 100
2.7 Screening of Test Organisms
Bacterial isolates which were obtained from
Sputum, air and patients with peridonatal disease
and preserved on Nutrient agar (Sigma- Aldrich
product) slant in the microbiology laboratory of
the Afe Babalola University Ado-Ekiti, Ekiti State,
Nigeria. The isolates include Esherichia coli,
Staphylococcus aureus, proteus mirabilis,
Bacillus cereus, Necropsobacter rosorum,
Tsukamurella hongkongensis, Lactobacillus sp,
Staphylococcus petrasii, Neisseria sicca, Dietzia
maris, Pseudomonas oryzyhabitans, Advenella
incenata, Neiserria subflava and Serriatia
marcescens. The stock cultures were inoculated
into freshly prepared nutrient agar to test for their
viability. They were stored at controlled
temperature for subsequent antibacterial
testing. Further subculturing was carried out
until pure cultures of the isolates were
obtained.
2.8 Antibacterial Screening
The Antibacterial susceptibility test was
performed by agar-well diffusion method using
Mueller-Hinton agar (Sigma - Aldrich product).
The test was performed under sterile condition.
The Mueller-Hinton agar was inoculated
separately with a suspension of each test
bacterial strain culture evenly spread with the
use of a sterile swab sticks on the entire surface
of each sterile surface of sterile Petri-dishes. The
agar was carefully punched using a cork-borer of
5mm in diameter. The extracts were dispensed
into the wells of the agar seeded with bacterial
isolates at different concentrations. The positive
antibacterial activities were established by the
presence of measurable zones of inhibition after
24 hours of incubation.
2.9 Antibiotics Susceptibility Testing
This test was carried out in order to determine
whether or not an etiological agent is sufficiently
sensitive to a particular antimicrobial agent to
permit its use for treatment. The test was
carried out with discs containing known
concentrations of the antibiotics to be used for
both Gram positive and Gram negative bacteria.
The test was carried out by making an even
spread of the pure isolates on prepared Meuller-
Hinton agar using sterile swab sticks and
aseptic placement of the particular disc meant
for Gram positive and negative bacteria. The
plates containing the discs were then
incubated at 37ºC for 24 hours. The plates are
evaluated based on the sizes of the zones
of inhibition of each of the antimicrobial
agents.
3. RESULTS
3.1 Proximate Composition of
Watermelon Seeds
The proximate composition of watermelon seeds
were carried out (Table 1). There was relatively
high moisture content of the sample, but
watermelon seeds had high percentage of
moisture content of 94.50% (Table 1). The
amount of carbohydrate content in watermelon
seeds were 62.22%. The protein content was
15.49%. The ash content for watermelon seed
was 64.60%. The fat content of watermelon seed
is 11% and lastly, the crude fibre content was
8.50% in watermelon seeds.
Sola et al.; IJBCRR, 27(1): 1-9, 2019; Article no.IJBCRR.46989
6
Table 1. Proximate composition of watermelon seeds
Parameters
Watermelon seeds (%)
Moisture 9.45±0.01
b
Ash 6.46±0.10
a
Protein 15.49±0.09
c
Crude fibre 8.50±0.002
a
Fat 1.10±0.001
a
Carbohydrate 59.03±1.20
d
(mean±SD; n=3)
Table 2. Phytochemical composition of watermelon seeds
Parameters (mg/g)
Watermelon seeds
Alkaloids ++
Phenols +
Tannins +
Saponins +
Flavonoids +
Keys: ++: Moderately present, +: Present, -: Absent
Table 3. Quantitative composition of watermelon seeds
Watermelon seeds
Alkaloids 3.080±0.02
c
Phenols 0.304±0.001
a
Tannins 0.147±0.005
a
Saponins 0.200±0.003
a
Flavonoids 2.675±0.01
b
(mean±SD; n=3)
Table 4. Vitamin composition in watermelon seeds
Sample
Vitamin B
1
(mg/100 g)
Vitamin B
2
(mg/100 g)
Vitamin B
3
(mg/100 g)
Vitamin B
6
(mg/100 g)
Vitamin B
12
(mg/100 g)
Watermelon
Seeds
0.030±0.01
a
0.01±0.0003
a
0.644±0.02
c
0.24±0.01
b
0.01±0.0001
a
3.2 Phytochemical Composition of
Watermelon Seeds
Phytochemical composition was carried out on
watermelon seeds to check for the presence of
phytochemical constituents which includes
alkaloids, phenols, saponins, flavonoids, tannin
(Table 2 and Table 3) and the result on the
qualitative composition of watermelon seeds
showed that alkanoids were moderately present,
tannin, saponins, flavonoids, and phenols were
all present. The quantitative analysis indicated
5.640mg/g for alkaloids, 0.015mg/g in phenols,
NP (not present) for tannins, 0.30mg/g in
saponins and NP (not present) in flavonoids. The
quantitative analysis for watermelon seeds
indicates 3.080mg/g of alkaloids, 0.304mg/g of
phenols, 0.117mg/g of tannins, 0.200mg/g of
saponins and 2.675mg/g of flavonoids.
3.3 Vitamin Composition
The vitamin composition of watermelon seeds
indicated 0.03 mg/100 g for vitamin B
1
, 0.01 for
vitamin B
2
, 0.64 mg/100 g for vitamin B
3
,
0.24 mg/100 g for vitamin B
6
and 0.01 for vitamin
B
12
.
3.4 Antibacterial Effect
Antibacterial effect of methanol extract of
watermelon seeds were carried out on the
bacterial isolates (Table 5). The results indicated
zones of inhibition on some organisms
according to certain concentration while some
did not show zones of inhibition i.e. the results
showed different sensitivity of the extract on
different organisms.
Sola et al.; IJBCRR, 27(1): 1-9, 2019; Article no.IJBCRR.46989
7
Table 5. Antibacterial effect of methanol extract of watermelon seeds on some selected
bacterial isolates
S/N
Organism
300 (mg/ml)
200 (mg/ml)
100 (mg/ml)
Control
1 Lactobacillus sp 12 0 0 0
2 Klebsiella pnuemoniae 0 0 0 0
3 Neisseria subflava 0 18 0 0
4 Necropsobacter rosorum 0 13 14 0
5 Pseudomonas
oryzihabitans
16 0 0 0
6 Neisseria sicca 0 17 0 0
7 Tsukmurella hongkongenis 0 0 0 0
8 Proteus mirabilis 0 0 0 0
9 Advenella incenata 0 0 0 0
10 Staphylococcus petrasii 0 0 0 0
11 Staphylococcus aureus 0 0 0 0
12 Neisseria sicca 0 0 0 0
13 Proteus mirabilis 0 0 0 0
4. DISCUSSION
In the present study, results showed that
watermelon seeds contained phytochemicals
including alkaloids, flavonoids, phenols, and
tannins. The role of these phytochemicals as
antimicrobial has been reported by many
researchers [8,9,10]. Their presence in
watermelon seeds were also reported by many
authors [11,8,12]. The presence of saponins in
this study was in contrast to the work reported by
[2], [13], but corresponds to that of [14,15]. The
disparity observed might be attributed to
differences in geographical location, factors like
climate, soil and propagation method. Presence
of these phytochemicals in the extract was a
clear indication of antimicrobial potentials of the
watermelon seeds extract. The nutritional
composition of watermelon seeds; it was
observed that watermelon seeds has higher
amount of Vitamin B
3
(Niacin) which is an
important nutrient, it helps lower cholesterol,
ease arthritis and boost brain function and helps
in function in digestive system, skin and nervous
system, the proximate composition analyzed
implies that the amount of carbohydrate was high
and this may implies that the sample can
regulate nerve tissue. Crude protein content
would serve as enzymatic catalyst, mediate cell
responses, control growth and cell differentiation
[16]. The moisture content of the leaf extract of
C. procera was 9.45%, too much of moisture in
any sample has been proved to cause caking
and also determine the storage and viability of
the growth of microorganisms [17].
Antibacterial activity of the extract showed that
not all the organisms tested were susceptible.
The methanol extract of watermelon seeds
produced only an effect on Neisseria subflava;
comparatively, different researchers have
reported contradictory observations in this
regards [18,19,20] observed that water extract
presents better response to the antibacterial
activities than the methanol whereas [18]
reported the contrary. This contradiction might be
a function of methodological differences and
strain variability.
5. CONCLUSION
Indiscriminate use of antimicrobial drugs has
created very dangerous drug resistance to
microbial strains; many bacterial strains have
developed resistance against antibiotics, such as
penicillin resistant Streptococcus pneumoniae,
methicillin resistant Staphylococcus aureus.
However previous records showed that even
new families of synthetic antimicrobial agents will
have short life expectancy. Researchers are
advised to turn their attention towards plants
products, which is most promising area in search
of new biologically active compounds with better
activity against multi drug resistant strains and
reduced antibiotic related side effects [21].
The activity observed is a clear indication of
therapeutic property possessed by the plant just
like other parts of Citrullus lanatus. Therefore,
the extract of watermelon seeds could be a good
source of antimicrobial agents and thus, should
be harnessed. Different governmental or private
sectors that are interested in agro industry area
recommend participating in this profitable area. If
this should be done, it would have significant
Sola et al.; IJBCRR, 27(1): 1-9, 2019; Article no.IJBCRR.46989
8
positive effect on the diversification of the Gross
Domestic Product (GDP) of Nigeria as well as
poverty and unemployment reduction.
Researchers should investigate further on the
production of watermelon in our country and the
benefits obtained from the product have to be
analyzed deeply to encourage the
pharmaceutical industries and other investors
locally. It is also important that more species of
pathogenic bacteria be tested in order to
ascertain the spectra of activities of the
antimicrobial substances present in watermelon
seeds.
COMPETING INTERESTS
Authors have declared that no competing
interests exist.
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... higher in concentration at 69.13 and 19.45 mg/kg of seeds. The WMSs also contain Vitamin B complex (B 1 , B 2 , B 3 , B 6 , B 9 and B 12 ) (Sola, Temitayo, Olufunke, & Shittu, 2019), vitamin E and K in different quantities. Awotedu et al. (2020) evaluated the vitamin content of WMSs and reported content of vitamin C (4.21 ± 0.69 mg/100 g), vitamin A (0.26 ± 0.04 mg/100 g), vitamin E (0.81 ± 0.05 mg/100 g) and vitamin B (0.12 ± 0.02 mg/100 g). ...
... The finding showed WMR/PVA nanofiber showed 83.5 ± 0.09% and 94 ± 0.8% area of inhibition of E. coli and S. aureus (Soliman, 2019). WMSs extracts were found to contain certain biologically active compounds such as saponins, tannins, alkaloid, glycosides, diterpenes, triterpenes, steroids, lactones, phenols and flavonoids have strong antimicrobial activity against multi-drug resistant strains i.e., Neisseria sicca, E. coli, Pseudomonas and Klebsiella pneumonia, etc. and reduced antibiotic-related side effects (Sola et al., 2019). Ethanolic extract of WMSs possesses excellent antimicrobial activity and can be used as an easily accessible source of natural antimicrobial agents (Hameed, Ali, Hafeez, & Malik, 2020). ...
Article
Background Agro-waste is of rising concern since they present social, economic and environmental challenges. Conversion of food waste is receiving an increasing attention towards the fact that these materials represent possible utilization sources for conversion into useful products and increasing the demand for natural bioactive compounds. Watermelon (Citrullus lanatus) is consumed all over the world that contains a large number of seeds and rind, which is discarded and used as animal feed. These by-products contain phytochemical compounds with great nutritional and functional potential. Scope and approach This review article describes the scientific studies from the last five years regarding the nutritional and bioactive compounds present in the watermelon rind (WMR) and watermelon seeds (WMSs). This review also focused on their nutraceutical worth fully justified by the presence of functional active compounds, as well as their potential industrial application for future research concerning novel or functional, nutraceutical, pharmaceutical and cosmeceutical product development. Key findings and conclusion WMR is a rich source of fatty acids, minerals, and phenolic compounds and dietary fibers. It also contains soluble carbohydrates (45-65%), carotenoids, alkaloids, saponin, and phytates. WMSs are an excellent source of protein (15-50%) such as albumin, globulin, prolamin, and glutelin. WMSs are also a good source of vitamin B-complex (B1, B2, B3, B6 B12), polyunsaturated fatty acids, essential and non-essential amino acids as well as phenolic compounds. Moreover. Watermelon by-products also present therapeutic properties including anti-diabetic, antioxidant, antihypertensive, anti-inflammatory, antiulcer, antitumor, hypocholesterolemic, hepato-, nephron- and neuro-protective effects and antibacterial properties fully evidenced from recently published literature. Therefore, the use of these byproducts to design and develop innovative functional food products with added value is important for sustainability across the food chain. Nevertheless, further research is needed on the clinical studies of WMR and WMSs to fully support the development of functional food products, nutraceutical and pharmaceutical applications.
... Due to the presence of various nutritious benefits the seeds of watermelon possess application in the field of several food products. Recently, Sola et al. [18] identified and quantified the phytochemicals in the methanol extracts derived from the seeds of watermelon. Furthermore, the report [18] evidenced the anti-bacterial property of watermelon seed extracts. ...
... Recently, Sola et al. [18] identified and quantified the phytochemicals in the methanol extracts derived from the seeds of watermelon. Furthermore, the report [18] evidenced the anti-bacterial property of watermelon seed extracts. The present review deals with various nutraceutical potentials of watermelon and its importance as an antioxidant, anti-cancerous, cardiovascular protectant, anti-inflammatory properties evidenced by in vitro and in vivo studies. ...
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Watermelon (Citrulus lantus) is an important horticultural crop which belongs to the Curcubitaceae family. The nutraceutical potential of watermelon has been illustrated by several researchers, which makes it a better choice of functional food. Watermelon has been used to treat various ailments, such as cardio-vascular diseases, aging related ailments, obesity, diabetes, ulcers, and various types of cancers. The medicinal properties of watermelon are attributed by the presence of important phytochemicals with pharmaceutical values such as lycopene, citrulline, and other polyphenolic compounds. Watermelon acts as vital source of l-citrulline, a neutral-alpha amino acid which is the precursor of l-arginine, an essential amino acid necessary for protein synthesis. Supplementation of l-citrulline and lycopene displayed numerous health benefits in in vitro and in vivo studies. Similarly, the dietary intake of watermelon has proven benefits as functional food in humans for weight management. Apart from the fruits, the extracts prepared from the seeds, sprouts, and leaves also evidenced medicinal properties. The present review provides a comprehensive overview of benefits of watermelon for the treatment of various ailments.
... The fruit comes in various shapes, sizes and 50 rind pattern. Although the seed of watermelon is often discarded as waste, but it content includes various amounts of carbohydrates, phenol, flavonoids, protein, 53,39 fiber, phosphorus and iron. Proximate analysis of the seeds revealed very high fat content (47.9%) followed 42,40 by protein (27.4%) and carbohydrates (10.0%). ...
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Cadmium is a toxic heavy metal that accumulates predominantly in soft tissues and as such is currently one of the most important occupational and environmental pollutants. The study evaluated the potential protective effects of watermelon seed oil on cadmium-induced toxicity in the cerebrum of male Wistar rats. Group 1 recieved 2 ml/kg of distilled water. Group 2 received 5 mg /kg bwt of cadmium chloride only. Group 3 received 5 mg /kg bwt of cadmium chloride + 500 mg / kg btw of CLSO as high dose. Group 4 received 5 mg /kg bwt of cadmium chloride + 250 mg / kg btw of CLSO as low dose. Group 5 received 5 mg /kg bwt of cadmium chloride + 10 mg / kg bwt of succimer. The administration was done through oral intubation and lasted 28 days. The experimental animals were observed daily and weighed weekly for physical changes. Neuro-behavioral study on anxiety related behaviors was th accessed weekly using elevated plus maze test. On the 29 day of the experiment, the final body weights were taken and euthanized using 75 mg /kg ketamine IP. The brain tissues were homogenized using 5 times (w/v) homogenizing buffer (pH 7.4). The homogenate was centrifuged at 4000 rpm to get the supernatant for biochemical analysis. While organ/ body weight revealed no significant changes, behavioral study show that Citrulus lanatus seed oil significantly (p<0.05) increased rearing frequency, grooming frequency and the number of entry into the open arm of the elevated plus maze relative to control. The biochemical assay showed statistically increased mean MDA across the groups when compared with the control (p <0.001). Although, there were statistical decrease SOD and GSH of the treated groups (p <0.001) when compared with the control, the mean CAT showed no significant difference across the groups in relation to the control. The histology showed that Co-treatment with CLSO prevented the neuronal degenerations of the cerebral cortex when compared with the control. CLSO ameliorated the effects of CdCl2-induced degeneration of cerebral cortex neurons, thus demonstrating its potential to protect cerebral cortex neurons from cadmium toxicity.
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