Total Phenolic Content, Total Flavonoid Content, Antioxidant and Antimicrobial Activities of Malaysian Shorea
Sharifah Aminah Syed Mohamad,
Nur Ainaa Atikah Mohd Nazri,
Siti Saidatul Akmar Ramli,
Sariza Natrah Mohd Kasim
Wan Zuraida Wan Mohd Zain
Five Shorea species which are endemic plants of Malaysia were used in
this study. The methanol extract of Shorea acuminata, Shorea macroptera,
Shorea leprosula, Shorea bracteolata and Shorea resinosa were
investigated for total phenolic contents (TPC), total flavonoid contents, radical
scavenging properties (DPPH), in vitro antioxidant and antimicrobial
activities. For the antimicrobial activity, the extracts were tested against
four bacteria; Gram negative bacteria Escherichia coli, Gram positive
bacteria Staphylococcus pyogenes, Staphylococcus aureus and Bacillus
subtilis and two fungi, Candida albicans and Aspergillus niger.
The result of TPC analysis showed that S. acuminata displayed highest
total phenolic content, 2731±0.09 mg/100 g, while in total flavonoid
content, S. resinosa displayed the highest amount of flavonoid, 956.73±0.01
mg/100 g. However, in DPPH analysis, the samples of S. resinosa, S.
macroptera and S. acuminate displayed better scavenging activity
as compared to butylatedhydroxytoluene (BHT). The in vitro antioxidant
activity indicated that S. macroptera showed the highest percent inhibition
both in ferric thiocyanate method (FTC) (98.68%) and thiobarbituric acid method
(TBA) analysis. In antimicrobial activity, S. resinosa displayed moderate
inhibition against Gram negative bacteria Escherichia coli, Gram positive
bacteria Streptococcus pyogenes, Staphylococcus aureus and Bacillus
subtilis. Other plants were found to display selective inhibition against
to cite this article:
Norhazana Norizan, Norizan Ahmat, Sharifah Aminah Syed Mohamad, Nur Ainaa Atikah Mohd Nazri, Siti Saidatul Akmar Ramli, Sariza Natrah Mohd Kasim and Wan Zuraida Wan Mohd Zain, 2012. Total Phenolic Content, Total Flavonoid Content, Antioxidant and Antimicrobial Activities of Malaysian Shorea. Research Journal of Medicinal Plants, 6: 489-499.
Received: November 05, 2011;
Accepted: March 31, 2012;
Published: June 21, 2012
Plants contain phytochemicals with various bioactivities, including antioxidant,
anti-inflammatory and anticancer activities. Currently, about 25% of the active
component was identified from plants that are used as prescribed medicines (Gill
et al., 2011). Several plants have been screened for their antioxidant
potential (Achuthan et al., 2003; Aniya
et al., 2002; Jose and Kuttan, 1995; Lin
et al., 1995; Nazri et al., 2011;
Shylesh and Padikkala, 1999) because the most practical
way to fight degenerative diseases is to increase antioxidant activity in our
body and that could be achieved by consumption of vegetables, fruits or edible
plants (Oboh and Akindahunsi, 2004; Oboh,
2005). Degenerative disease is caused by free radicals in our body that
are able to damage living tissues and cause cell death (Yang
et al., 2002). Several plant extracts and chemical constituents have
been found to show quite prominent antioxidant activity (Tripathi
et al., 1996; Vani et al., 1997; Oseni
and Akindahunsi, 2011). According to Chu et al.
(2002), the majority of the antioxidant activity may come from active substances
such as flavonoid, isoflavone, flavone, anthocyanin, catechin and iso-catechin
rather than from vitamin C, E and β-carotene.
Most lowland rainforests in Malaysia are dominated by the Dipterocarpaceae
family. About 67% of the total growing stock in Sabah and Sarawak is estimated
to consist of Shorea, a common dipterocarp genus. Shorea is locally
known as Meranti in Malaysia and for this study, five Shorea species
namely S. acuminata (Meranti rambai daun), S. bracteolata (Meranti
Paang), S. leprosula (Meranti Tembaga), S. resinosa (Meranti
Belang), S. macroptera (Meranti Melantai) were investigated for their
potential as antioxidant and antimicrobial agent.
Our previous study on the chemical constituents of Shorea revealed the
presence of oligostilbenoids as the main constituents (Norizan
et al., 2011; Nazri et al., 2011;
Zawawi and Ahmat, 2011). Oligostilbenoids found in Shorea
species has been reported to possess important bioactivities such as antibacterial
(Sotheeswaran et al., 1983) and 5α-reductase
reactions (Hirano et al., 2001) while oligostilbenoids
from other family also showed significant bioactivities such as antitumor (Ito
et al., 2003), acetylchloinesterase (Sung et
al., 2002), ecdysteroid antagonist (Sarker et
al., 1999), anti HIV agent (Dai et al., 1998),
anti-inflammation (Kitanaka et al., 1990), cytotoxic
(Dai et al., 1998) and antioxidant activities
(Tanaka et al., 2000). This paper describes the
evaluations of total phenolic content (TPC), total flavonoid content, radical
scavenging properties (DPPH), in-vitro antioxidant capacity using ferric
thiocyanate (FTC) and thiobarbituric acid (TBA) methods as well as in-vitro
antimicrobial activity of five Shorea species which are S. acuminata,
S. macroptera, S. leprosula, S. bracteolata and S. resinosa.
MATERIALS AND METHODS
The plant samples were collected from Jengka Reserve Forest, Selangor, Malaysia
in 2009 and voucher specimens were submitted to the Herbarium of Universiti
Teknologi MARA, Pahang (UiTM), S. bracteolata (DO8/06/09), S. macroptera
(DO7/06/09), S. acuminate (D11/06/09), S. resinosa (D10/06/09)
and S. leprosula (DO9/06/09). The samples were cut into smaller pieces
and ground into fine powder. The plants were macerated with methanol five times
at room temperature, filtered, evaporated using rotary evaporator and the weight
of the crude extracts recorded.
Antioxidant activity assay
Total phenolic content (TPC): The TPC was carried out according to Velioglu
et al. (1998) method. The 0.01 g of crude extracts was appropriately
diluted with 5 mL of methanol and 0.1 mL of the diluted sample was added with
Folin-Ciocalteu phenol reagent and placed about 20 min in a dark place. 1.5
mL of 20% Na2CO3 solution were added to the sample and
shaken vigorously. The solution was immediately marked up with distilled water
and mixed thoroughly. The absorbance was measured at 760 nm using Perkin Elmer
Lambda 35 UV-visible Spectrophotometer after incubation for 2 h in dark and
at room temperature. A calibration curve was prepared, using the regression
equation of the calibration curve of gallic acid (y = 0.013x, r2
= 0.998) and contents were expressed as mg gallic acid equivalent (GAE)/100
g of sample.
Total flavonoid content (TFC): Two milliliter of 2% AlCl3
in ethanol was added to 2 mL of the test sample and left in the dark at room
temperature for 1 h. The UV absorption was measured at 420 nm. Concentration
of 0.1 mg mL-1 sample solutions were used while routine concentrations
of 0.02-0.12 mg mL-1 were used to obtain a calibration curve of quercetin
(y = 2.519x+0.002, r2 = 0.999). Determinations were performed in
Radical scavenging assay (DPPH): The DPPH radical-scavenging activity
was determined by using the method proposed by Nazri et
al. (2011) with some modification. The positive control was prepared
by adding 4 mL of quercetin (0.05 mg mL-1) to 1 mL of DPPH (0.4 mg
mL-1), whereas the negative control was prepared by each solvents
used and 1 mL of DPPH solution. The radicals stock solution was prepared
fresh daily. The DPPH solution (1 mL) was added to 3 mL of polyphenol extracts
with different concentrations (200, 400, 600, 800, 1000 and 1200 ppm). The mixture
was shaken vigorously and allowed to stand at room temperature in the dark for
10 min. The decrease in absorbance of the resulting solution was monitored at
517 nm for 10 min. Lower absorbance of the reaction mixture indicates higher
free radical-scavenging activity. Radical scavenging activity is expressed as
the inhibition percentage (IP) and was calculated as follows:
The decolouration was plotted against the sample extract concentration and
a logarithmic regression curve was established in order to calculate the IC50
(inhibitory concentration at 50%) which is the amount of sample extract (concentration)
necessary to decrease by 50% the absorbance of DPPH.
Ferric thiocyanate method (FTC): Four milligrams of the dried solids
from each fraction were dissolved in 4.0 mL of ethanol absolute and added with
4.1 mL of a 2.51% linoleic acid solution in EtOH and 8 mL of a 0.05 M phosphate
buffer (pH 7.0). The mixture was incubated at 40°C in a dark screw-cap vial.
During the incubation, 1.0 mL aliquot was taken from the mixture and added with
9.7 mL of 75% ethanol, followed by the addition of 0.1 mL of 30% ammonium thiocyanate.
Precisely 3 min after the addition of 0.1 mL of 0.02 M ferrous chloride in 3.5%
hydrochloric acid, the absorbance for the red color was measured at 500 nm .
Thiobarbituric acid method (TBA): Two milliliters of 0.67% thiobarbituric
acid and 1.0 mL of 20% trichloroacetic acid solutions were added to 2.0 mL of
the mixture solution containing linoleic acid which was prepared according to
the FTC procedure. The mixture was then placed in a boiling water bath for 10
min. After cooling, the mixture was centrifuged at 3000 rpm for 20 min and the
absorbance was measured at 532 nm.
Antimicrobial activity test
Microorganisms: The extracts were tested against four bacteria that are
Gram negative bacteria, Escherichia coli and Gram positive bacteria,
Streptococcus pyogenes, Staphylococcus aureus and Bacillus subtilis
and yeast, Candida albicans and fungus, Aspergillus niger.
Preparation of antimicrobial disc: The micropipette was used to place
20 μL extract onto a 6 mm diameters of sterile antimicrobial disc. The
disc was aseptically dried and placed on media inoculated with the tested microorganisms
by using sterile forceps. A maximum of only four discs were placed on the media.
The plates were incubated at 37°C for 24 h. The corresponding concentrations
are expressed in terms of mg of extract per mL of solvent.
Disc diffusion method: Antimicrobial tests were carried out by disc
diffusion method using the suspension containing 1x108 CFU mL-1
bacteria or 1x106 CFU mL-1 yeast on Nutrient Agar (NA)
or Potato Dextrose Agar (PDA), respectively. The discs were impregnated with
20 μL of extracts and placed on the inoculated agar. The inoculated plates
were incubated for 24 h at 37°C for bacteria strains, 48 h for yeast. A
sterile cotton swab was dipped into 18-24 h broth culture of the test organism
and carefully streaked over the surface of the sterile agar plate. The plate
was then turned at right angles and the swab was streaked again over the entire
surface to ensure a uniform film of the test microbes. 0.02 mg mL-1.
Streptomycin was used as a positive control for the bacteria whereas 100 mg
mL-1 cycloheximide was used as positive control for the yeast. Antimicrobial
activity was evaluated by measuring the inhibition zone against the test organisms.
The assay in this experiment was repeated three times.
Statistical analysis: The experiments were done in triplicate. The result
was given as the mean±SD. Analysis of Variance (ANOVA) was used for the
analysis of data. Significance was accepted at p = 0.05.
RESULTS AND DISCUSSION
Five Shorea species, S. acuminata, S. macroptera, S.
leprosula, S. bracteolata and S. resinosa which are endemic
plants of Malaysia were investigated for their total phenolic content, total
flavonoid content, in vitro antioxidant and antimicrobial activities.
The results showed that all Shorea species tested with TPC displayed
high amount of phenolic with range of 2461-2731 mg/100 g GAE. Among the five
Shorea samples, S. acuminata extracts displayed the highest phenolic
content 2731.00±0.09 mg/100 g followed by S. leprosula extracts
2615.38±0.01 mg/100 g, S. resinosa extracts 2461.54±0.01
mg/100 g and S. macroptera extracts 2461.54±0.01 mg/100 g and
the lowest total phenolic content is given by S. bracteolata extract
with 2423.08±0.02 mg/100 g which is considered still very high. Most
of the crude methanol extracts of these Shorea species gave total phenolic
contents in the range of 2461.54±0.01 mg of GAEs to 2731.00±0.09
mg of GAEs and are presented in Table 1. Plant phenols are
a major group of compounds acting as primary antioxidants or free radical scavengers
(Kahkonen et al., 1999) due to their hydroxyl
groups (Diplock, 1997) which contribute directly to
the antioxidative action. Phenolic compounds are effective hydrogen donors,
making them good antioxidants (Rice-Evans et al.,
In the TFC analysis, all Shorea extracts tested displayed moderate flavonoid
content with range of 535.93-956.73 mg g-1. S. resinosa displayed
highest amount of flavonoid content 956.73±0.01 mg g-1 followed
by S. leprosula (873.36± 0.002 ), S. acuminate ( 851.48±0.001)
and S. bracteolata (766.18± 0.001) while the lowest given by S.
macroptera extracts 535.93±0.02 mg g-1.
|| Extraction yields, phenolic and flavonoid contents of Malaysian
|Values are means of triplicate, Different superscript in column
indicate significant different at p<0.05, na: Not available
|| Percent inhibitions of Shorea species by FTC method
(day 6, 1 ppm)
The total flavonoid contents findings for these Shorea extracts were
summarized in Table 1. The analysis of TFC indicates that
Shorea contain considerable amount of flavonoids.
In DPPH radical scavenging activity, S. resinosa, S. macroptera
and S. acuminata displayed better scavenging activity as compared to
the standard BHT with % scavenging of 92.50, 88.23 and 87.23, respectively (Fig.
1). Percent scavenger for BHT is 79.7%. S. bracteolata and S.
leprosula showed lower % of scavenging activity (46.55 and 34.55%, respectively)
when compared to BHT. The highest scavenger is shown by S. resinosa,
while the lowest scavenger is S. leprosula. S. resinosa. S. macroptera
and S. acuminata demonstrated significant free radical scavenging ability
by giving IC50 values of 0.125, 0.140 and 0.125 μg mL-1,
respectively as shown in Table 1 and are considered as excellent
scavenger and even better than the standard BHT. The methanol extracts of S.
bracteolata and S. leprosula did not give any values of IC50.
The IC50 value is defined as the concentration that causes a decrease
in the initial amount of DPPH radicals by 50% (Huang et
al., 2005). It is the concentration where the active crude extract will
exhibit 50% of antioxidant activity (Chiang et al.,
2003) and crude extracts exhibit 50% of inhibition at concentration less
than 20 μg mL-1. These concentrations are considered positive
for antioxidant activity (Geran et al., 1972).
In FTC analysis, three of the Shorea species namely S. resinosa,
S. leprosula and S. macroptera, exhibited strong antioxidant potential
with percent inhibition between 71.11-98.68% while Quercetin and vitamin E showed
percent inhibition of 99.68% and 93.45%, respectively (Fig. 2).
The extract of S. Macroptera (98.68%) showed the highest percent inhibition
and as good as the standard as its % inhibition is better than vitamin E. The
other two of the Shorea extracts demonstrated moderate antioxidant activity
at 56.75% for S. bracteolata and 57.47% for S. acuminata, respectively.
|| Percent inhibition of Shorea sp. between FTC and TBA
method (day 6,1 ppm)
|Values are means of triplicate, Different superscript in column
indicate significant different at p<0.05, when compared five with standard,
FTC: Ferric thiocyanate, TBA: Thiobarbituric acid
The total antioxidant property of the methanol extracts of Shorea species
is given as follows in descending order: S. macroptera>S. leprosula>S.
resinosa> S. acuminate> S. bracteolata at 98.68, 78.42,
71.11, 57.47 and 56.75%, respectively.
The findings of this study showed that FTC results of the five Shorea
species do not correlate with TPC and TFC results. The extracts of S. macroptera
displayed highest antioxidant activity, 98.68% among the five Shorea
species but its TPC values was the lowest amongst the five Shorea species
2461.54±0.01 mg g-1 and its TFC values was also the lowest
(535.93±0.02). On the other hand, the extracts of S. acuminata
displayed lowest antioxidant activity 54.79% but recorded the highest of TPC
values, 2731.00±0.09 mg g-1 and moderate amount of flavonoid
content (851.48±0.001) as shown in Table 1.
The plant extracts tested showed low absorbance values, indicating a high level
of antioxidant activity. None of the plant extracts showed absorbance values
greater than the negative controls (without plant extracts) at the end point
of both methods, indicating the presence of antioxidant activity. However, the
plant extracts of S. macroptera exhibited strong antioxidant activity
as determined by both the FTC and TBA methods, surpassing the activity of the
standard antioxidant, vitamin E. The extract of S. macroptera indicated
the highest antioxidant as its absorbance was the lowest and located between
both standards as shown in Table 2.
FTC test is related to the peroxide formation in the initial stage of lipid
oxidation, while TBA test measures the amount of malondialdehyde (MDA) at later
stage. The results in FTC showed higher inhibition than in TBA. This may indicate
that the amount of peroxide in the initial stage of lipid peroxidation is much
greater than the amount of peroxide in the secondary stage. This is due to the
MDA, produced on the final day of the incubation period (1 day after the control
reached maximum) is a very unstable compound and turn into alcohol and acid
which cannot be detected by spectrophotometer (Ottolenghi,
1959) which might cause mutagenic and cytotoxic events (Zin
et al., 2002). At a low pH and high temperature (100°C), MDA
binds TBA to form a red complex that can be measured at 532 nm after incubation
for 24 h. By determining the amount of malondialdehyde (MDA), the correlation
between both FTC and TBA methods can be verified. These results correlated well
with those obtained previously, using the FTC method. A comparison between FTC
and TBA measured is shown in Fig. 3.
For the analysis of antimicrobial activity, the methanol extracts of Shorea
species were tested against four microbes: Escherichia coli, Streptococcus
pyogenes, Staphylococcus aureus, Bacillus subtilis and yeast including
Candida albicans and Aspergillus niger. S. acuminata extract
(25-100 mg mL-1) inhibited the growth of S. pyogenes (7.0-10.0
mm) and S. aureus (6.0-12.0 mm) moderately at higher concentration, 100
mg mL-1 and weakly at a lower concentration, 25 mg mL-1.
||Lipid oxidation profile of methanol extract of Shorea
sp. in linoleic acid buffer model system
The inhibition zone was increased by 1 mm with the increment of 25 mg mL-1
dose of S. acuminata methanol extract. B. subtilis, E. coli, C. albicans
and A. niger were found resistant against this methanol extract.
S. macroptera, S. leprosula, S. bracteolata and S. resinosa were
able to inhibit S. aureus and B. subtilis in a dose dependant
manner with the highest inhibition was shown by S. Leprosula extract
(25-100 mg mL-1) against B. Subtilis (11-15 mm) and S.
resinosa extract (25-100 mg mL-1) against S. pyogenes
(9-15 mm) both at 100 mg mL-1 while the lowest inhibition were displayed
by S. acuminata against S. aureus (6 mm) at 25 mg mL-1.
All species were found able to inhibit S. aureus in a dose dependant
manner. It is interesting to note that only S. resinosa was able to inhibit
the growth of E. coli, a microbe commonly found in the lower intestine
of warm-blooded organisms. The best result was given by S. resinosa which
was able to inhibit the growth of four gram negative and gram positive microbes
that are S. pyogenes, S. aureus, B. subtilis and E. coli.
S. macroptera and S. bracteolata were able to inhibit the growth
of three microbes: S. pyogenes, S. aureus and B. subtilis while
S. acuminate and S. Leprosula only inhibited two microbes which are
S. pyogenes and S. aureus and S. aureus and B. subtilis, respectively
also in dose dependant manner. It is clearly shown from the results tabulated
in Table 3 that none of the Shorea species was able
to inhibit the growth of the two tested yeast C. albicans and A. niger.
The result indicated that most of the Shorea extracts was able to inhibit
gram positive bacteria (S. pyogenes, S. aureus, B. subtilis) as compared
to gram negative bacteria (E. coli). This is further confirmed by the
previous studies by Kelmanson et al. (2000), Masika
and Afolayane (2002), Masoodi et al. (2008),
Karaman et al. (2003), Khanahmadi
et al. (2010) and Zongo et al. (2010)
that describe the high sensitivity of gram positive bacteria towards plant extracts
and their component.
According to Zakaria (1991), E. coli was the
bacteria strains not susceptible to most plant extracts which could be observed
from the result of this study. These could be due to several possible reasons,
in which the distinctive feature of gram-negative bacteria is the presence of
a double membrane surrounding each bacterial cell. Although, all bacteria have
an inner cell membrane, gram-negative bacteria have a unique outer membrane.
|| Zone of inhibition of the methanol extracts of Shorea
|Values are means of triplicate, different superscript in a
same row indicate significant different at p<0.05
This outer membrane excludes certain drugs and antibiotics from penetrating
the cell, partially accounting for why gram-negative bacteria are generally
more resistant to antibiotics than other gram-positive bacteria. This could
be the beginning for further research on the screening approach by taking into
consideration the extracts preparation and the mechanism of action. E. coli
in this study also exhibited the same pattern in which it was resistant to almost
all extracts. However, S. resinosa methanol extract is capable of moderately
inhibiting E. coli growth. Although, S. resinosa methanol extract
could inhibit bacteria, it was still unable to inhibit the two fungi C. albicans
and A. niger.
S. resinosa showed good antimicrobial activity in which its methanol
extract inhibited the growth of all Gram-positive and Gram-negative bacteria
but not the fungi. It also gave good IC50 values 0.125 μg mL-1,
that may be regarded as good antioxidant agent. There were differences in cell
wall structure between Gram-positive and Gram-negative bacteria, with the gram-negative
outer membrane acting as a barrier to many environmental antimicrobial substances,
including antibiotic. The results from the antimicrobial activity of five Shorea
species may come from resveratrol oligomers which constitute as the major compound.
As a conclusion, S. resinosa methanol extract exhibited good antimicrobial
activity against S. pyogenes, S. aureus, B. subtilis and
E. coli while S. macroptera showed the highest inhibition in both
FTC and TBA assays. The results of this study have revealed the potential of
Malaysian Shorea as antioxidant and antimicrobial agents.
The authors would like to thank Faculty of Applied Sciences, Universiti Teknologi
MARA, Malaysia for financing this research project. Two of the authors were
granted scholarships by UiTM fellowship and National Science Fellowship.
Achuthan, C.R., B.H. Babu and J. Padikkala, 2003.
Antioxidant and hepatoprotective effects of Rosa damascena
. Pharm. Biol., 41: 357-361.CrossRef | Direct Link |
Aniya, Y., C. Miyagi, A. Nakandakari, S. Kamiya, N. Imaizumi and T. Ichiba, 2002.
Free radical scavenging action of the medicinal herb Limonium wrightii
from the Okinawa islands. Phytomedicine, 9: 239-244.PubMed |
Chiang, L.C., W. Chiang, M.Y. Chang, L.T. Ng and C.C. Lin, 2003.
Anti-leukemic activity of selected natural products in Taiwan. Am. J. Chinese Med., 31: 37-46.PubMed |
Chu, Y.F., J. Sun, X. Wu and R.H. Liu, 2002.
Antioxidant and antiproliferative activities of common vegetables. J. Agric. Food Chem., 50: 6910-6916.CrossRef | PubMed | Direct Link |
Dai, J.R., Y.F. Hallock, J.H. Cardellina and M.R. Boyd, 1998.
HIV-inhibitory and cytotoxicity oligostilbenes from the leaves of Hopea malibato
. J. Nat. Prod., 61: 351-353.
Diplock, A.T., 1997.
Will the 'good fairies' please prove to us that vitamin E lessens human degenerative disease? Free Radic. Res., 27: 511-532.PubMed |
Geran, R.I., N.H. Greenberg, M.M. Macdonald, A.M. Schumache and B.J. Abbot, 1972.
Protocols for screening chemical against animal tumor and other biological systems. Cancer Chemo. Reprod., 3: 1-103.
Gill, N.S., J. Bajwa, P. Sharma, K. Dhiman and S. Sood et al
Evaluation of antioxidant and antiulcer activity of traditionally consumed Cucumis melo
seeds. J. Pharmacol. Toxicol., 6: 82-89.CrossRef | Direct Link |
Hirano, Y., R. Kondo and K. Sakai, 2001.
Compounds inhibitory to rat liver 5α-reductase from tropical commercial wood species: Resveratrol trimers from melapi (Shorea
sp.) heartwood. J. Wood Sci., 47: 308-312.Direct Link |
Huang, D., B. Ou and R.L. Prior, 2005.
The chemistry behind antioxidant capacity assays. J. Agric. Food Chem., 53: 1841-1856.CrossRef | PubMed | Direct Link |
Ito, T., Y. Akao, H. Yi, K. Ohguchi and K. Matsumoto et al
Antitumor effect of resveratrol oligomers against human cancer cell lines and the molecular mechanism of apoptosis induced by vaticanol C. Carcinogenesis, 24: 1489-1497.Direct Link |
Jose, J.K. and R. Kuttan, 1995.
Antioxidant activity of Emblica officinalis
. J. Clin. Biochem. Nut., 19: 63-70.CrossRef | Direct Link |
Kahkonen, M.P., A.I. Hopia, H.J. Vuorela, J.P. Rauha, K. Pihlaja, T.S. Kujala and M. Heinonen, 1999.
Antioxidant activity of plant extracts containing phenolic compounds. J. Agric. Food Chem., 47: 3954-3962.CrossRef | PubMed | Direct Link |
Karaman, I., F. Sahin, M. Gulluce, H. Ogutcu, M. Sengul and A. Adiguzel, 2003.
Antimicrobial activity of aqueous and methanol extracts of Juniperus oxycedrus
L. J. Ethnopharmacol., 85: 231-235.CrossRef | PubMed | Direct Link |
Khanahmadi, M., S.H. Rezazadeh and M. Taran, 2010. In vitro
antimicrobial and antioxidant properties of smyrnium cordifolium boiss. (Umbelliferae) extract. Asian J. Plant Sci., 9: 99-103.
Kelmanson, J.E., A.K. Jager and J. van Staden, 2000.
Zulu medicinal plants with antibacterial activity. J. Ethnopharmacol., 69: 241-246.CrossRef | PubMed | Direct Link |
Kitanaka, S., T. Ikezawa, K. Yasukawa, S. Yamanouchi, M. Takido, H.K. Sung and I.H. Kim, 1990.
(+)-Α-viniferin, an anti-inflammatory compound from Caragana chamlagu
root. Chem. Pharm. Bull., 38: 432-435.PubMed |
Lin, J.M., C.C. Lin, M.F. Chen, T. Ujiie and A. Takata, 1995.
Scavenging effects of Mallotus repandus
on active oxygen species. J. Ethnopharmacol., 46: 175-181.
Masika, P.J. and A.J. Afolayane, 2002.
Antimicrobial activity of some plants used for the treatment of livestock diseases in Eastern Cape, South Africa. J. Ethnopharmacol., 83: 129-134.CrossRef |
Masoodi, M.H., B. Ahmed, I.M. Zargar, S.A. Khan, S. Khan and P. Singh, 2008.
Antibacterial activity of whole plant extract of Marrubium vulgare
. Afr. J. Biotechnol., 7: 86-87.Direct Link |
Nazri, N.A.A.M., N. Ahmat, A. Adnan, S.A.S. Mohamad and S.A.S. Ruzaina, 2011. In vitro
antibacterial and radical scavenging activities of Malaysian table salad. Afr. J. Biotechnol., 10: 5728-5735.Direct Link |
Norizan, N., N. Ahmat and Z. Shameeri, 2011.
Isolation of three oligostilbenes from the bark of Shorea bracteolate
. Planta Medica, 77: 1334-1334.
Oboh, G., 2005.
Effect of blanching on the antioxidant properties of some tropical green leafy vegetables. Food Sci. Technol., 38: 513-517.CrossRef | Direct Link |
Oboh, G. and A.A. Akindahunsi, 2004.
Change in the ascorbic acid, total phenol and antioxidant activity of sun-dried commonly consumed green leafy vegetables in Nigeria. Nutr. Health, 18: 29-36.CrossRef | Direct Link |
Oseni, O.A. and A.A. Akindahunsi, 2011.
Some phytochemical properties and effect of fermentation on the seed of Jatropha curcas
L. Am. J. Food Technol., 6: 158-165.CrossRef | Direct Link |
Ottolenghi, A., 1959.
Interaction of ascorbic acid and mitochondrial lipid. Arch. Biochem. Biophys., 79: 355-363.
Rice-Evans, C.A., N. Miller and G. Paganga, 1997.
Antioxidant properties of phenolic compounds. Trends Plant Sci., 2: 152-159.CrossRef | Direct Link |
Sarker, S.D., P. Whiting, L. Dinan, V. Sik and H.H. Rees, 1999.
Identification and ecdysteroid antagonist activity of three resveratrol trimers (Suffruticasols A, B, and C) from Paeonia suffruticosa
. Tetrahedron, 55: 513-524.Direct Link |
Shylesh, B.S. and J. Padikkala, 1999.
Antioxidant and anti-inflammatory activity of Emilia sonchifolia
. Fitoterapia, 70: 275-278.
Sotheeswaran, S., M.U.S. Sultanbawa, S. Surendrakumar and P. Bladon, 1983.
Polyphenols from dipterocarp species. Copalliferol A and stemonoporol. J. Chem. Soc., 1: 159-162.
Sung, S.H., S.Y. Kang, K.Y. Lee, M.J. Park and J.H. Kim et al
(+)- α-Viniferin, a stilbenetrimer from Caragana chamlague
, inhibit acetylchlorinesterase. Biol. Pharm. Bull., 25: 125-127.
Tanaka, T., T. Ito, K. Nakaya, M. Iinuma and Y. Takahashi et al
Vaticanol D, a novel resveratrol hexamer isolated from Vatica rassak
. Tetrahedron Lett., 4: 7929-7933.Direct Link |
Tripathi, Y.B., S. Chaurasia, E. Tripathi, A. Upadhyay and G.P. Dubey, 1996. Bacopa monniera
Linn. as an antioxidant: Mechanism of action. Indian J. Exp. Biol., 34: 523-526.PubMed | Direct Link |
Vani, T., M. Rajani, S. Sarkar and C.J. Shishoo, 1997.
Antioxidant properties of the ayurvedic formulation Triphala and its constituents. Int. J. Pharm., 35: 313-317.CrossRef | Direct Link |
Velioglu, Y.S., G. Mazza, L. Gao and B.D. Oomah, 1998.
Antioxidant activity and total phenolics in selected fruits, vegetables and grain products. J. Agric. Food Chem., 46: 4113-4117.CrossRef | Direct Link |
Yang, J.H., H.C. Lin and J.L. Mau, 2002.
Antioxidant properties of several commercial mushrooms. Food Chem., 77: 229-235.CrossRef | Direct Link |
Zakaria, M., 1991.
Isolation and characterization of active compounds from medicinal plants. Asia Pac. J. Pharmacol., 6: 158-220.
Zawawi, N.K.N. and N. Ahmat, 2011.
Isolation of trimer stilbenoids from the bark of Shorea maxwelliana
. Planta Medica, 77: 1333-1333.
Zin, Z.M., A. Abdul-Hamid and A. Osman, 2002.
Antioxidative activity of extracts from Mengkudu (Morinda citrifolia
L.) root, fruit and leaf. Food Chem., 78: 227-231.CrossRef | Direct Link |
Zongo, C., A. Savadogo, L. Ouattara, I.H.N. Bassole and C.A.T. Ouattara et al
Polyphenols content, antioxidant and antimicrobial activities of Ampelocissus grantii
(Baker) Planch. (Vitaceae): A medicinal plant from Burkina Faso. Int. J. Pharmacol., 6: 880-887.CrossRef | Direct Link |