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Pak. J. Pharm. Sci., Vol.28, No.1, January 2015, pp.129-134 129
Antioxidant and antibacterial activities of extracts
from Conyza bonariensis growing in Yemen
Riyadh Abdulmajid Saleh Thabit, Xiang-Rong Cheng, Xue Tang, Jin Sun,
Yong-Hui Shi and Guo-Wei Le1*
State K. Laboratory of Food Science and Technology, School of Food Science and Technology,
Jiangnan University, Wuxi, PR China
Abstract: This study aims to examine the antioxidant and antibacterial activities and phenolic contents of Conyza
bonariensis growing in Yemen. The whole plants of C. bonariensis were ultrasonically extracted by ethanol. The
antioxidant activity of the extract was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene bleaching
(BCB). The effectiveness of the extract on the growth inhibition of some indicators of foodborne illness bacteria were
investigated by agar well diffusion assay. The total phenols (TP), total flavonoids (TF), total tannins (TT), and total
anthocyanins (TA) were determined by Folin-Ciocalteu method, aluminium chloride method, Folin and Ciocalteu
method, and pH-differential method, respectively. The extract of C. bonariensis possessed TP 144.1 mg/g, TF 143 mg/g,
TT 0.99mg/g, and TA 0.97mg 100g, with 94.57% inhibition of DPPH and 92.47% inhibition of BCB, and strong
inhibitory effects against tested bacteria, which was approximate to those of peel extract of Punica granatum.
Keywords: Antioxidant, antibacterial, Conyza bonariensis, Punica granatum, total Phenolic
INTRODUCTION
Recently, various extracts of plants have gained special
interest as sources of natural antioxidant and antibacterial
agents (Madhavi and Salunkhe, 1995). Natural
antioxidants are compounds from plant or animal sources.
Phenolics are regarded as antioxidants and found in
significant quantities in vegetables, fruits, spices and
seeds. They also have roles in food industry and in
chemoprevention of diseases (Noguchi and Niki, 2000).
The oxidation reactions are involved in aging and
progression of several diseases, while antioxidant
molecules may slow down the aging process, disease
progression, and prolong the life span (Gutteridge and
Halliwell, 2010).
Conyza bonariensis (L.) Cronq is an annual plant spread
widely all over the world, from North America to Europe.
The plant C. bonariensis grows spontaneously in central
Yemen and is used in folk medicine headache, dental
pain, treat rheumatism, cystitis and nephritis (Soheir et
al., 2012). In addition it was approved in medicine as a
hemostatic, possibly an anthelminthic, pungent tonic,
astringent to control bleeding and as a diuretic (Lenfeld et
al., 1986).
This research aims to assess the antioxidant and the
antibacterial activities of Conyza bonariensis growing in
Yemen, and its (TP (TF), (TT) and (TA) compared to
extracts of Punica granatum which is contained high
phenolic contents and possesses strong antioxidant and
the antibacterial activities (Zarei et al., 2010).
MATERIAL AND METHODS
Chemicals and machine
Tert-butylhydroquinone (TBHQ), 2,2-diphenyl-1-
picrylhydrazyl (DPPH), ascorbic acid (Vitamin C), Folin-
Ciocalteu reagent, gallic acid, quercetin reagent, β-
carotene, and linoleic acid were from Sigma (USA).
Ethanol, dimethylsulfoxide (DMSO), aluminium chloride,
potassium acetate, potassium chloride, sodium acetate and
Tween 20 were from Sinopharm chemical regent co. ltd.
Spectrophotometer (Shanghai-Techcomp, UV 2300),
balance (Shanghai-Mettle Toledo, AB 204-N), rotary
evaporator (Shanghai-Biochemical Equipment), water
bath (Shanghai-Hengzi), pH metter (Shanghai-Mettler
Toledo), incubation (Shanghai-Hengzi), and ultrasonic
(Wuxi-Kejie Ultrasonic Electronic Equipment Co. Ltd,
KJ-300) were also used in the study.
Plant materials
The whole plants of C. bonariensis and peels of Punica
granatum (L.) were collected in September 2012 from
Taiz region (Yemen). The identification of plant materials
were carried out by the Agricultural Research Authority
(Taiz).
Preparation of extracts
The plant samples were air-dried in shade, twenty grams
from plant were extracted with 600ml of 90% ethanol in
an ultrasonic device at room temperature. The ethanol
extract was filtered and the residues were re-percolated
for three times and solvent was removed using a rotary
evaporator. Dried extracts were kept refrigerated until
use.
*Corresponding author: e-mail: lgw@jiangnan.edu.cn
Antioxidant and antibacterial activities of extracts from Conyza bonariensis growing in Yemen
Pak. J. Pharm. Sci., Vol.28, No.1, January 2015, pp.129-134
130
Total phenols (TP)
The TP was determined spectrophotometrically according
to the Folin-Ciocalteu’s method (Arnnok et al., 2012).
Using a six-point calibration curve, the total phenolics
were determined by a comparison of the values obtained
with the calibration curve of gallic acid (fig. 1). The
results were expressed as mg gallic acid equivalents
(gallic acid/g extract).
Total flavonoids (TF)
Flavonoids in the examined plant extracts were
determined spectrophotometrically using aluminium
chloride according to the reported method (Lin and Tang,
2007). Quercetin was used as a standard. The
concentration of flavonoids was in (mg/ml) on the
calibration line and the total flavonoid was expressed as
mg/g of dry extracts (fig. 2).
Total tannins (TT)
The TT were estimated by Folin and Ciocalteu method
(Tamilselvi et al., 2012). Using a five-point calibration
curve, the TT were determined by a comparison of the
values obtained with the calibration curve of gallic acid
(fig. 3), total tannins values are expressed in terms of
gallic acid equivalent (mg/g of dry extracted).
Total anthocyanin (TA)
The TA was determined by the pH-differential method
(Guisti and Wrolstad, 2001). Was calculate the
absorbance (A) of the diluted sample as follows:
A=(A510–A700) pH 1.0 – (A510–A700) pH 4.5.
Calculate anthocyanin pigment concentration as follows:
Monomeric anthocyanin pigment (mg/L) = (A × MW ×
DF × 1000)/(ε × 1), and it was converted to mg of total
anthocyanin content per 100 g sample.
Antioxidant activity of extracts
Determination of antioxidant activity (AA) using DPPH
radical scavenging method
In this assay, the (AA) of plant extracts was evaluated by
measuring the bleaching of the purple-colored ethanolic
solution of DPPH (Burits and Bucar, 2000). The
antioxidant activity of six different concentrations (0.2,
0.1, 0.05, 0.02, 0.01 and 0.005mg/ml) of plant extracts
was measured in terms of hydrogen donating or radical
scavenging ability (Brand et al., 1995). The inhibitory
concentration (IC50) value represented the concentration
of the plant extracts that caused 50% inhibition.
Determination of antioxidant activity using β-Carotene
bleaching (BCB) assay
The (AA) of extracts was evaluated by the β-carotene
according to method (Lu and Foo, 2000). The
measurement was carried out every 30 min intervals.
While TBHQ and Vitamin C. both were at 200 ppm, and
were used as standards.
Microbial strains and media
Shigella dysenteriae CMCC 51302, Escherichia coli
ATCC 25922, Salmonella typhimurium CMCC 50013,
Streptococcus pyogenes ATCC 12344 and
Staphylococcus aureus ATCC 25923 were provided by
the Microbiology Lab in School of Food Science and
Technology, Jiangnan University, Wuxi 214122, P. R.
China. Each culture was activated by transferring a
loopful into nutrient broth (4 ml) followed by incubation
at 37ºC±1ºC for 16 h. The optical density of each active
culture was adjusted at 615(nm) using fresh broth to give
a standard inoculums of 108 (CFU)/ml.
Determination of antibacterial activity
It was studied by the agar well diffusion method (Smania
et al., 1999). Briefly, Agar media were perforated with 6
mm-diameter holes, aseptically cut and filled with 100 µl
of plant extracts. The extracts were used in the
concentration of 5, 10, and 20 mg/ml from extract of
dimethylsulphoxide (DMSO). Streptomycin and
Penicillin were used as a reference antibacterial, whereas
DMSO was the negative control. The plates were
incubated at 37ºC±1ºC for 21 h and then examined to
verify inhibition. A positive result was defined as
inhibition zone of 9 mm or more around the holes.
STATISTICAL ANALYSIS
Statistical methods were used of three simultaneous
assays to calculate means and standard deviations.
Statistical analysis (SPSS, 16) was applied to the data to
determine differences (P<0.05) performed by ANOVA.
RESULTS
Total phenolics and total flavonoids
The content of polyphenols was 144.1 and 134.4 mg/g in
C. bonariensis and P. granatum, respectively (table 1).
The results indicated significant differences (P0.05)
among extracts, C. bonariensis contained higher phenol
content compared to P. granatum extracts.
Fig. 1: Calibration curve for gallic acid (mg/g of dry
extract)
There were significant differences (P<0.05) as the extract
of C. bonariensis had higher flavonoid content, while the
extract of P. granatum containd less flavonoids
Riyadh Abdulmajid Saleh Thabit et al
Pak. J. Pharm. Sci., Vol.28, No.1, January 2015, pp.129-134 131
Fig. 2: Calibration curve for quercetin (mg/g of dry
extracts.)
Total tannins and total anthocyanins
From the data presented in table 1, it is apparent that the
tannin content of extracts varied significantly (P<0.05).
Tannins were low in P. granatum (0.91 mg/g) and high in
C. bonariensis (0.99 mg/g), which also had the highest
level of total phenolics.
Fig. 3: Calibration curve for gallic acid (mg/g of dry
extracted)
The present study found that there were significant
differences (P<0.05) among study samples. The highest
anthocyanins content was in C. bonariensis
(0.97mg/100g), where the smallest was in P. granatum
(0.63mg/100g).
Antioxidant activity using (DPPH) radical scavenging
Extracts of C. bonariensis and P. granatum inhibited
antioxidant activities of 94.57% and 92.92% scavenging
DPPH, respectively at a concentration of 0.05 mg/ml
(table 2).
Antioxidant activity using β-Carotene bleaching assay
There were no significant differences (P 0.05) among
the study samples (table 2). Results showed that extracts
of C. bonariensis and P. granatum were better inhibitors
of β -carotene bleaching than reference antioxidants like
TBHQ (table 2).
The DPPH radical scavenging IC50 values of extracts
were summarized in table 2. Extracts of C. bonariensis
and P. granatum exhibited strong DPPH radical
scavenging with IC50 values at 4.93 and 4.95 µg/ml,
respectively. Two extracts tested in the DPPH assay had
good antioxidant properties (fig. 4).
Fig. 4: DPPH radical scavenging activities of extracts
from C. bonariensis and P. granatum and reference
antioxidants (VC and TBHQ)
Fig. 5: Antioxidant activity of extracts from C.
bonariensis and P. granatum and standard antioxidants in
β-carotene-linoleate bleaching system
The BCB absorbance of C. bonariensis and P. granatum
for 120 min were 0.188 and 0.152, respectively, whereas
they were 0.192 and 0.148 at zero time, respectively (fig.
5).
Fig. 6: Antibacterial activity of extracts: (A) C.
bonariensis on S. aureus, (B) C. bonariensis on S.
typhimurium, and (C) P. granatum on S. aureus, using 5,
10, and 20 mg/ ml of each extract.
Antibacterial activity
Presents antibacterial activities of the two plants tested at
concentrations of 5, 10, and 20 mg/ml (table 3). It showed
that gram positive bacteria (Staphylococcus and
Antioxidant and antibacterial activities of extracts from Conyza bonariensis growing in Yemen
Pak. J. Pharm. Sci., Vol.28, No.1, January 2015, pp.129-134
132
Streptococcus) were more susceptible to extracts from C.
bonariensis and P. granatum. S. aureus was the most
sensitive organism to C. bonariensis extracts at 20 mg/ml
than S. pyogenes. Gram negative bacteria were
susceptible to extracts from C. bonariensis than P.
granatum. Extracts of C. bonariensis and P. granatum
were inhibitory for S. typhimurium and S. dysenteriae. E.
coli was more strongly inhibited by extract of C.
bonariensis than that of P. granatum.
Extracts of C. bonariensis appeared to be the most
effective with the zone of inhibition sizes ranging
from14.6 to 19.8 mm at 20 mg/ml, as shown in fig. 6.
DISCUSSION
Polyphenols are some of the most occurring
phytochemicals in plants. Moreover, these phenolic
contribute to quality and nutritional value. Also contribute
to color and sensory characteristics of fruits and
vegetables and also play an important role in providing
protection against in vivo and in vitro oxidation, and have
plant defense mechanisms to counteract reactive oxygen
species (ROS) and prevent damage of micro organisms.
Phenolic compounds are antioxidant working as a free
radicals scavenger (Shahidi and Wanasundara, 2003). The
phenolics and flavonoids are considered as important
indicators of antioxidant capacity.
Some studies indicated of P. granatum extract had phenol
content between 124.43 and 91.2 mg/g (Ahmed, 2012;
Mutahar et al., 2012), respectively. C. bonariensis
extracts were 167.9 mg/g (Durre et al., 2012).
There is a strong correlation between antioxidant activity
and total phenols in table 2. These findings suggest that
total phenols are a good predictor of antioxidant activities.
Investigations reported that phenolic concentrations
varied from 5 to 46% of peel P. granatum extracts (Li et
al., 2006; Negi and Jayaprakasha, 2003). The variability
of total phenolic in this study could be partially attributed
to differences in solvents used for extracting peels,
geographic sources of samples and varieties.
Phenolic contents are affected by plant species, maturity
at harvest, post harvest, soil conditions and growing
conditions (Nasır et al., 2011). The results of the extract
P. granatum were consistent with the previous study,
which the TF in the extract of P. granatum was 59.44
mg/g (Ahmed, 2012).
Tannins are natural polyphenols ubiquitously distributed
in plants, such as vegetables, fruits and seeds (Elías et al.,
2009). Commercially tannins are used in the wine
industry for a multitude of reasons: to stabilize the color
of red wines, ensure palate balance and complexity in
wines, inhibit lacasse in botrytis-infected fruit and to
serve as fining agents to reduce protein concentrations
(Luz et al., 2008). These results of extract P. granatum
were also reported in a previous study (Hakime et al.,
2012). Anthocyanins are responsible for the red and blue
colors in some plants (Concepcion et al., 2003).
There were significant differences (p<0.05) among in the
extracts of C. bonariensis and P. granatum. That was
probably due to the presence of high polyphenolic
content. Also could be related to the presence of hydroxyl
and carbonyl groups (Galati and Brien, 2004; Payet et al.,
2005). And also due to the fact that radical-scavenging
capacity is directly related to the hydrogen donating
ability of compounds (Lucarini et al., 1990). The
antioxidant efficiency of the extracts tested was basically
dependent on their concentrations. The extracts of C.
bonariensis and P. granatum maintained stability and the
strength of antioxidative activities were related to the
Phenolic concentrate.
The antioxidant activity of extracts was also assessed by
the ability to prevent β-Carotene from oxidation by
linoleic acid. The oxidation of linoleic acid generates
peroxyl free radicals due to the abstraction of a hydrogen
from diallylic methylene groups (Kumaran and Joel
Karunakaran, 2006). The BCB antioxidant activities are
stable with time. Extracts of C. bonariensis and P.
granatum exhibited strong BCB activities, possibly due to
Table 1: Total phenols, flavonoids, tannins and anthocyanins in extracts of C.bonariensis and P.granatum (means±SD)
Plant Total phenols
(mg GAE/g)
Flavonoids
(mg quercetin/g)
Tannins
(mg GAE/g)
Anthocyanins
(mg/100g)
C. bonariensis 144.1a±5.32 134.0a±5.87 0.99a ±0.02 0.97a ±0.02
P. granatum 134.4
b
±3.24 79.3
b
±0.36 0.91
b
±0.02 0.63
b
±0.02
Table 2: Antioxidants activity by DPPH scavenging and β-carotene bleaching of C. bonariensis and P. granatum
extracts (means ± S.D)
Extraction DPPH scavenging test β-carotene bleaching test
Inhibition of DPPH (%) (0.05 mg/ml) IC50 (µg/ml) Inhibition of BCB (%) (5 mg/ml)
C. bonariensis 94.57
b
±0.16 4.93
b
±0.15 92.4a±3.15
P. granatum 92.92c±0.10 4.95
b
±0.05 90.77a±0.21
VC 95.01a±0.12 5.21c±0.05 6.37c±3.12
TBHQ 95.12a±0.09 2.14a±0.04 84.60
b
±2.25
Values are means of three independent analyses.
Riyadh Abdulmajid Saleh Thabit et al
Pak. J. Pharm. Sci., Vol.28, No.1, January 2015, pp.129-134 133
their oil components, such as tocopherols, phytosterols,
and phenolic compounds. The synthetic antioxidant
TBHQ had a stronger antioxidant activity when compared
to VC (fig. 5).
Confirmed the scientific literature on the importance of
antibacterial activity of the extracts, which are designed to
provide extended shelf life safety food microbial. In this
study the antibacterial activity of two plant extracts was
assessed by diffusion method agar well. All extracts
tested showed antibacterial abilities against S. aureus, S.
pyogenes, S. dysenteriae and S. typhimurium.
The results may support the use of C. bonariensis and P.
granatum in traditional medicines.
Gram negative bacteria were more resistant than gram-
positive bacteria, which were also reported by (Ahmad
and Beg, 2001). The resistance towards antibacterial
substances by gram-negative bacteria were related to the
lipopolysaccharides in their cell wall (Gao et al., 1999;
Alzoreky and Nakahara, 2003). The results of the present
study are encouraging as extracts of C. bonariensis
showed significant antibacterial activity against many
enteric pathogens tested.
CONCLUSION
This study showed that the two plants used in traditional
medicine in Yemen have antioxidant and antibacterial
activities. The types and contents of bioactive components
varied among different plants. The characterization of the
active components of those plants may lead to full
utilization of these plants by the local folks.
ACKNOWLEDGEMENTS
The study was supported by the 12th Five-Year Plan for
Science and Technology Development (No.2012BAD
33B05), Chinese Nature Science Foundation (21403601
and 31201805), Fundamental Research Funds for the
Central Universities (JUSRP111A36, JUSRP1052), and
Priority Academic Program Development of Jiangsu
Higher Education Institutions.
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