Kesum (Polygonum minus)

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*Corresponding author.
Email: kama@ukm.my
Tel: 03-89215990; Fax: 03-89213232
International Food Research Journal 18: 526-531 (2011)
Maizura, M., *Aminah, A. and Wan Aida, W. M.
School of Chemical Sciences and Food Technology,
Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600
Bangi, Malaysia
Introduction
Antioxidants are recognized for their potential
in promoting health and lowering the risk for cancer,
hypertension and heart disease (Wolfe and Liu, 2003;
Valko et al., 2007). The uses of natural antioxidants
from plant extracts have experience growing
interest due to some human health professionals and
consumer’s concern about the safety of synthetic
antioxidants in foods (Sun and Ho, 2005; Suhaj, 2006).
Antioxidant activities in plants have been identied
by many researchers (Hinneburg et al., 2006; Kumar
et al., 2006; Cousins et al., 2007) and their effects
in chicken sausage have been studied by Noriham
et al., (2005). The natural occurring antioxidant
is focused more on edible plants, especially spices
and herbs (Huda-Faujan et al., 2009; Nanasombat
and Teckchuen, 2009). Spices and herbs are an
excellent source of phenolic compounds (avonoids,
phenolic acid and alcohols, stilbenes, tocopherols,
tocotrienols), ascorbic acid and carotenoids which
have been reported to show good antioxidant activity
(Zheng and Wang 2001). Generally, Malaysian foods
are rich in spices and herbs including kesum, ginger
and turmeric. The whole of kesum is normally use
when making gravy for laksa (wet rice noodle), while
ginger and turmeric can be added into various foods
as whole spices, powder or extracts. However, direct
use of these spices and herbs as antioxidant is limited
due to their aromatic and pungent properties.
Numerous studies had showed good antioxidant
activity of kesum (polygonum minus) (Vimala et al.,
2003; Huda-Faujan et al., 2009), ginger (zingiber
ofcinale) (Hinneburg et al., 2006; Kim et al., 2007;
Kota et al., 2008) and turmeric (curcuma longa)
(Kaur and Kapoor, 2002; Tangkanakul et al., 2009).
In Thailand and Vietnam, kesum is known as Pak
pai or Vietnamese mint (Ra and Vastano, 2007).
According to Nanasombat and Teckchuen (2009),
kesum contained avonoids such as rutin (3.77%),
catechin (0.34%), quercetin (0.08%), isorhamnetin
(0.01%) and kaempferol (0.01%) which had showed
to have antioxidant activity.
Ginger is commonly use in food as spice. Kim et
al., (2007) and Schwertner and Rios (2007) reported
that the main components of ginger are 6-gingerol,
6-shogaol, 8-gingerol and 10- gingerol and these
constituents had exhibited strong antioxidative
activity.
Generally turmeric has been used as dye and
spice. Turmeric is an important tropical spice mainly
for its colour, aroma and antioxidant property. The
yellow colour in turmeric are mainly due to the
presence of 3 major pigments; curcumin 1,7-bis(4-
hydroxy-3-methoxyfenil)-1,6-heptadiene-3,5-
dione), demethoxy-curcumin and bis demethoxy-
Total phenolic content and antioxidant activity of kesum
(Polygonum minus), ginger (Zingiber ofcinale) and
turmeric (Curcuma longa) extract
Abstract: Herb and spices namely kesum, ginger and turmeric were extracted by using juice extractor without
the additional of solvent. These herb and spices were determined for moisture content and the extracts were
analyzed for total phenolic content (TPC) and antioxidant activity (DPPH radical scavenging assay and FRAP
ferric-reducing antioxidant power assay). The yield of kesum, ginger and turmeric extraction was 23.6%, 58.6%
and 66.4%, respectively. The results showed that, there was signicant difference (P < 0.05) in total phenolic
content and antioxidant activity for kesum, ginger and turmeric extracts. Kesum extract had the highest total
phenolic content followed by ginger and turmeric extract. A signicant and positive high Pearson’s correlations
between TPC and DPPH assay (r = 0.86) and between TPC and FRAP assay (r = 0.91) respectively was observed
for all plants extracts. This indicated that phenolic compounds were the main contributor of antioxidant activity
in plants. However, there was no synergistic effect observed for all plants extract mixture.
Keywords: Kesum, ginger, turmeric, phenolic content, DPPH radical scavenging assay, ferric –reducing antioxidant
power assay

46 Maizura, M. Aminah, A. and Wan Aida, W. M.
International Food Research Journal 18: 526-531
curcumin. These curcuminoids are known to have
high antioxidant activities (Ishita et al., 2004; Sharma
et al., 2005; Cousins et al., 2007).
The objectives of this research was to determine
the total phenolic content (TPC) and antioxidant
activity of kesum, ginger and turmeric by using
Folin-Ciocalteau method, DPPH-free radical
scavenging method and ferric-reducing antioxidant
power assay (FRAP) method. The correlation of TPC
with DPPH and FRAP assay of plants extracts were
investigated.
Materials and Methods
Materials
Fresh plant materials namely kesum (Polygonum
minus), ginger (Zingiber ofcinale) and turmeric
(Curcuma longa) were purchased from local market
in Selangor. Folin-Ciocalteu’s (FC) phenol reagent
was obtained from Merck (Darmstadt, Germany).
Sodium carbonate, gallic acid, 1,1-diphenyl-2-
picrylhydrazyl (DPPH) and 2,4,6,-Tris (1-pyridyl)-
5-triazine (TPTZ) were purchased from Sigma
(Steinheim, Germany), and ferrous sulphate was
obtained from R&M Chemicals (Essex, UK).
Determination of moisture content
Moisture content was determined by drying 5 g
of samples (kesum, ginger and turmeric) at 105oC in
a drying oven to a constant weight (AOAC, 1990).
Preparation of plant extracts and determination of
yield
Two hundred gram of fresh kesum (Leaves and
stem), peeled ginger and turmeric were washed with
clean water followed by surface drying using oven at
37oC for 30 mins. The extracts were obtained by using
juice extractor (Breville Juice Fountain® Plus Juice
extractor, Australia) without any addition of water.
Then, the pure plant extracts were ltered using lter
paper (Whatman No 1) followed by centrifugation
(Hermle GmbH, Germany) at 4750 g (4oC) for 15
mins. The extracts were collected and stored in air
tight glass vials covered with aluminium foil and
kept at - 4oC. Sample extract mixtures (kesum:
ginger: turmeric) with different ratios (1:0:0, 1:1:0,
0:1:0, 0:1:1, 0:0:1, 1:0:1 and 1:1:1) were prepared
before analyzed. The percentage of yield extracts was
calculated as % yield = [Weight of sample extract /
Initial weight of sample] x 100.
Determination of total phenolics
Total phenolic contents of all plants extracts were
determined using Folin-Ciocalteu reagent as described
by Singlaton and Rossi (1965). Samples were inserted
into different test tube and mixed thoroughly with 5
ml Folin-Ciocalteu reagent (previously pre-dilute
10 times with distilled water). After 5 mins, 4 ml
of 7.5% sodium carbonate (Na2CO3) was added and
allowed to react for 2 hrs at room temperature. The
absorbance was measure at 765 nm using microplate
reader spectrophotometers (Molecular devices,
VERSAmax tunable, California, USA). Samples
were measured in three replicates. Standard curve of
gallic acid solution (10, 20, 40, 60, 80 and 100 ppm)
was prepared using the similar procedure. The results
were expressed as mg GAE/100 g extract sample.
Determination of free radical scavenging using
DPPH method
The antioxidant activities of all extracts were
evaluated through free radical scavenging effect on
1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The
determination was based on the method proposed
by Akowuah et al. (2005). Two ml of 0.1mM DPPH
methanolic solution was added into 200 µl of sample
extracts and 0.8 ml methanol. The mixture was
thoroughly mixed and kept in the dark for 1 hr. The
control was prepared by mixing 2 ml of DPPH and
1 ml methanol. The absorbance was measure at 517
nm using microplate reader spectrophotometers
(Molecular devices, VERSAmax tunable, California,
USA). Samples were measured in three replicates.
Percentage of DPPH scavenging activity was
calculated as % inhibition of DPPH = [Abs control
–Abs sample / Abs control] x 100.
Determination of ferric reducing/antioxidant power
assay (FRAP)
FRAP assay was carried out according to the
method of Benzie and Strain (1996). FRAP reagent
was prepared from acetate buffer (1.6 g sodium
acetate and 8 ml acetic acid make up to 500 ml) (pH
3.6), 10 mM TPTZ solution in 40 mM HCL and
20 mM iron (III) chloride solution in proportion of
10:1:1 (v/v) respectively. The FRAP reagent was
prepared fresh daily and was warmed to 37oC in oven
prior to use. A total of 50 μl samples extract were
added to 1.5 ml of the FRAP reagent and mixed well.
The absorbance was measured at 593 nm using using
microplate reader spectrophotometers (Molecular
devices, VERSAmax tunable, California, USA) after
4 mins. Samples were measured in three replicates.
Standard curve of iron (II) sulfate solution (200,
400, 600, 800 and 1000 ppm) was prepared using
the similar procedure. The results were expressed as
μmol Fe (II) /100 g extract sample.

Total phenolic content and antioxidant activity of kesum (Polygonum minus), ginger (Zingiber ofcinale) and turmeric (Curcuma longa) extract 47
International Food Research Journal 18: 526-531
Statistical analysis
Experiment data were analyzed using Excel
(Microsoft Inc.) and SPSS version 17.0 software.
Signicant differences between samples were
analyzed using analysis of variance (ANOVA) and
Duncan’s multiple-range test (P< 0.05). Pearson’s
correlation was used to determine the correlation of
data between DPPH free radical-scavenging activity
(%) and ferric reducing/antioxidant power assay
(µmol Fe (II)/g extract) on total phenolic content (mg
GAE/100 g extracts). Data obtained were reported as
mean ± standard deviation.
Results and Discussions
Moisture content and extraction yield
Results showed that, mean moisture content of
kesum, ginger and turmeric in this study was 84.5%,
91.5% and 91.0 % respectively. Analysis of extraction
showed that turmeric had the highest yield which is
66.2%. It seemed that more than 50% of moisture
content of turmeric had been extracted. The yield of
ginger extracted was 57.8%, while kesum had the
lowest yield of extraction (23.6%).
Total phenolic content
Total phenolic contents of plants extract were
tested using the diluted Folin-Ciocalteu reagent.
Table 1 showed total phenolic content of plants
extracts. Result clearly showed that kesum had the
highest total phenolic content followed by ginger and
turmeric which mean value of 165.34 mg GAE/100 g
extract, 101.56 mgGAE/100 g extract and 67.89 mg
GAE/100 g extract, respectively. In the present study,
the mixture of kesum and ginger extract (132.0 mg
GAE/100 g extract) showed signicantly increased
(p<0.05) in total phenolic content compared to single
ginger extracts. There was no signicant different
(P>0.05) observed in total phenolic content for the
mixture of kesum and turmeric (103.3 mg GAE/100
g extracts) with the total phenolic content for the
mixture of kesum, ginger and turmeric (104.7 mg
GAE/100 g extracts).
Antioxidant capacity
DPPH radical was used as a stable free radical to
determined antioxidant activity of natural compounds
(Ozturk et al., 2007). The antioxidant activity of plant
extracts containing polyphenol components is due
to their capacity to be donors of hydrogen atoms or
electrons and to capture the free radicals (Stoilova et
al., 2007). Thus, the purple colour of 2,2-diphenyl-1-
picryl hydrazyl (DPPH) will reduce to α, α-diphenyl-
β-picrylhydrazine (yellow coloured) (Akowuah et
al., 2005). According to Suhaj (2006) scavenging
of the stable radical (DPPH) is considered a valid
and easy assay to evaluate scavenging activity of
antioxidants.
Results of the activity of free radical scavenging
of plants extracts are presented in Table 2. Results
showed that, kesum extract contained the highest
DPPH radical scavenging activity (82.6 ± 0.7%),
followed by ginger extract (79.0 ± 0.6%) and turmeric
extract (64.6 ± 2.4%). Mixture of kesum and ginger
(79.4 ± 1.2%) extract did not show signicant (P
> 0.05) increased in the antioxidant activity when
compared to single ginger extract. In contrast, mixture
of kesum and turmeric (73.4 ± 2.7%) extract and the
mixture of ginger and turmeric (68.6 ± 1.8%) extract
had showed signicantly (P<0.05) higher antioxidant
activity when compared to single turmeric extract.
The natural presence of antioxidants in plants
and a combination with other antioxidants may have
an additive effect (that is expected from a simple
addition) and synergistic effect (an effect which is
greater than individual or sum of the combination)
(Fuhrman et al., 2000). Studied by Graversen et al.
(2008) and Roberts and Gordon (2003) found that
plant polyphenols have a synergistic effect with other
antioxidants present in plant material. In addition,
other studies have also been carried out to analyze
the synergistic effect of antioxidants (Liu et al.,
2008; Altunkaya et al., 2009; Romano et al., 2009).
However, antioxidant activity in this study did not
show synergistic effect in plant extract mixture.
In this study, the antioxidant activity is also
determined on the basis of the ability of antioxidant
in this plants extracts to reduce ferric (III) iron to
ferrous (II) iron in FRAP reagent (Alothman et al.,
2009; Wong et al., 2006). Generally, FRAP assay was
used due to its simplicity and reproducibility. Table 2
shows the antioxidant activity of plants extracts. The
results indicated that kesum exhibited signicantly
(P < 0.05) higher antioxidant activity (46.3 ± 1.2
µmol Fe (II)/g) compared to ginger (26.2 ± 0.0 µmol
Fe (II)/g) or turmeric (23.3 ± 0.9 µmol Fe (II)/g).
Antioxidant activity of plants mixtures of kesum and
ginger; kesum and turmeric; and ginger and turmeric
were 34.4 µmol Fe (II)/g, 27.5 µmol Fe (II)/g and 25.3
µmol Fe (II)/g, respectively. There was no synergistic
effect observed for antioxidant activity in any plants
mixture. In addition, the result demonstrated that
antioxidant activity of plants extracts by FRAP assay
had similar trend with DPPH assay except for mixture
of kesum, ginger and turmeric extracts.

48 Maizura, M. Aminah, A. and Wan Aida, W. M.
International Food Research Journal 18: 526-531
Spices and herb extracts Total phenolic (mg GAE/100g
extracts)
Polygonum minus 165.3 ± 1.0a
Zingiber ofcinale 101.6 ± 0.6d
Curcuma longa 67.9 ± 1.0f
Polygonum minus: Zingiber
ofcinale (1:1) 132.0 ± 1.9b
Polygonum minus: Curcuma longa
(1:1) 103.3 ± 1.1cd
Zingiber ofcinale : Curcuma longa
(1:1) 73.6 ± 1.2e
Polygonum minus: Zingiber
ofcinale : Curcuma longa (1:1:1) 104.7 ± 1.2c
Table 1. Mean ± SD of total phenolic content of fresh spices and herb
extracts
Values are mean (n=3) ± standard deviation. Values with the same superscript letter within each column are not
signicant different (p>0.05).
Spices and herb extracts DPPH inhibition
(%)
FRAP (µmol
Fe (II)/ g
extracts
Polygonum minus 82.6 ± 0.7a46.3 ± 1.2a
Zingiber ofcinale 79.0 ± 0.6b26.2 ± 0.0cd
Curcuma longa 64.6 ± 2.4e23.3 ± 0.9e
Polygonum minus: Zingiber
ofcinale (1:1) 79.4 ± 1.2b34.4 ± 1.1b
Polygonum minus: Curcuma longa
(1:1) 73.4 ± 2.7c27.5 ± 0.7c
Zingiber ofcinale : Curcuma longa
(1:1) 68.6 ± 1.8d25.3 ± 0.7d
Polygonum minus: Zingiber
ofcinale : Curcuma longa (1:1:1) 78.1 ± 0.8b23.1 ± 0.2e
Table 2. DPPH inhibition and ferric reducing/antioxidant power assay
of spices and herb extracts
Values are mean (n=3) ± standard deviation. Values with the same superscript letter within each column are not
signicant different (p>0.05).
y = 0.1712x + 56.789
R² = 0.7328
60
65
70
75
80
85
90
60 80 100 120 140 160 180
DPPH free radical-scavenging
activity (%)
Tota l ph enoli c con tent (mg GAE/ 100 g extract)
Figure 1. The correlation between total phenolic content and antioxidant activity
(DPPH free radical-scavenging activity) of plants extracts
y = 0.2265x + 5.2286
R² = 0.822
20
25
30
35
40
45
50
60 80 100 120 140 160 180
Ferric reducing/antioxidant power
assay (µmol Fe (II)/ g extract)
Tota l ph enoli c con tent (mg GAE/ 100 g ex tract)
Figure 2. The correlation between total phenolic content and ferric reducing/
antioxidant power assay (FRAP) of plants extracts
The correlation between total phenolic content and
antioxidant activity
Several studies (Shan et al., 2005; Wu et al.,
2006; Wong et al., 2006) reported that phenolic
compounds in spices and herbs signicantly
contributed to their antioxidant properties. Figure 1
shows the correlation between total phenolic content
and DPPH assay of plants extracts. Results shows
a positive correlation coefcient between the total
phenolic content and DPPH assay of plants extracts
(r=0.86) which is highly signicant (p<0.01). Figure
2 shows the correlation between total phenolic
content and FRAP assay of plants extracts and the
results also demonstrated highly positive correlation
coefcient between the total phenolic content and the
FRAP assay of the plants extract (r=0.91), that was
highly signicant (p<0.01). Meanwhile, coefcient
of determination (R2) was measured on how well
the regression line represents the data which shows
the association between total phenolic content and
DPPH assay (R2=0.73) in Figure 1 and between
total phenolic content and FRAP assay (R2=0.82)
in Figure 2. In this study, it seemed that, the higher
total phenolic content of plants extracts resulted in
higher antioxidant activity as similarly reported by
Cai et al., (2004), Shan et al., (2005) and Wong et al.,
(2006). A signicant and linear relationship existed
between the antioxidant activity and phenolic content
of kesum, ginger and turmeric, thus indicating that
phenolic compounds are major contributors to
antioxidant activity.
Conclusion
The results obtained demonstrated that kesum
had the highest total phenolic content and antioxidant
activity compared to ginger and turmeric. The mixture
of plants extracts had showed no synergism effect.
There was a good correlation between total phenol
content and antioxidant activity (DPPH and FRAP
assay) that support the idea of phenols as contributor
of the antioxidant power of plants extracts.
Acknowledgement
The authors would like to thank the Universiti
Kebangsaan Malaysia for the nancial support
(GUP grant –NBT-08-27-103) for this research.
Acknowledgment goes to Universiti Sains Malaysia
for the nancial support for the rst author.
References
Akowuah, G.A., Ismail, Z., Norhayati, I. and Sadikun,
A. 2005. The effects of different extraction solvents
of varying polarities of polyphenols of Orthosiphon
stamineus and evaluation of the free radical-scavenging

Total phenolic content and antioxidant activity of kesum (Polygonum minus), ginger (Zingiber ofcinale) and turmeric (Curcuma longa) extract 49
International Food Research Journal 18: 526-531
activity. Food Chemistry 93: 311-317.
Alothman, M., Bhat, R. and Karim, A.A. 2009. Antioxidant
capacity and phenolic content of selected tropical fruits
from Malaysia, extracted with different solvents. Food
Chemistry 115: 785-788.
Altunkaya, A., Becker, E.M., Gokmen, V. and Skibsted,
L.H. 2009. Antioxidant activity of lettuce extract
(Lactuca sativa) and synergism with added phenolic
antioxidants.Food Chemistry 115: 163-168.
AOAC 1990. Methods of Analysis: 15th Ed. Washington,
DC: Association of Ofcial Analytical Chemists.
Benzie, I.F.F. and Strain, J.J. 1999. Ferric reducing /
antioxidant power assay: Direct measure of total
antioxidant activity of biological uids and modied
version for simultaneous measurement of total
antioxidant power and ascorbic acid concentration.
Methods in Enzymology 299: 15-27.
Cai, Y., Luo, Q., Sun, M. and Corke, H. 2004. Antioxidant
activity and phenolic compounds of 112 Chinese
medicinal plants associated with anticancer. Life
Sciences 74: 2157–2184.
Cousins, M., Adelberg, J., Chen, F. and Rieck, J. 2007.
Antioxidant capacity of fresh and dried rhizomes from
four clones of turmeric (Curcuma longa L.) grown in
vitro. Industrial Crops and Products 25: 129-135.
Fuhrman, B., Volcova, N., Rosenblat, M. and Aviram, M.
2000. Lycopene synergistically inhibits LDL oxidation
in combination with vitamin E, glabridin, rosmarinic
acid, carnosic acid, or garlic. Antioxidants and Redox
Signalling 2: 491-505.
Graversen, H.B., Becker, E.M., Skibsted, L.H. and
Andersen, M.L. 2008. Antioxidant synergism between
fruit juice and alpha-tocopherol. A comparison
between high phenolic black chokeberry (Aronia
melanocarpa) and high ascorbic blackcurrant (Ribes
nnigrum). European Food Research and Technology
226 (4): 737-743.
Hinneburg, I., Damien Dorman, H.J. and Hiltunen, R.
2006. Antioxidant activities of extracts from selected
culinary herbs and spices. Food Chemistry 97: 122-
129.
Huda-Faujan, N., Noriham, A., Norrakiah, A.S. and Babji,
A.S. 2009. Antioxidant activity of plants methanolic
extracts containing phenolic compounds. African
Journal of Biotechnology 8(3): 484-489.
Ishita, C., Kaushik, B., Uday, B. and Ranjit, K.B. 2004.
Turmeric and curcumin: biological actions and
medicinal applications. Current Science 87: 44-53.
Kaur, C. and Kapoor, H.C. 2002. Antioxidant activity
and total phenolic content of some Asian vegetables.
International Journal of Food Science and Technology
37: 153-161.
Kim, J.K., Kim, Y., Na, K.M., Surh, Y.J. and Kim, T.Y.
2007. [6]-Gingerol prevents UVB-induced ROS
production and COX-2 expression in vitro and in vivo.
Free Radical Research 41: 603-614.
Kota, N., Krishna, P. and Polasa, K. 2008. Alterations in
antioxidant status of rats following intake of ginger
through diet. Food Chemistry 106: 991-996.
Kumar, G.S., Nayaka, H., Dharmesh, S.M. and Salimath,
P.V. 2006. Free and bound phenolic antioxidants in
amla (Emblica ofcinalis) and turmeric (Curcuma
longa). Journal of Food Composition 19: 446-452.
Liu, D., Shi, J., Ibarra, A.C., Kakuda, Y. and Xue, S.J.
2008. The scavenging capacity and synergistic effects
of lycopene, vitamin E, vitamin C, and β-carotene
mixtures on the DPPH free radical. Lebensmittel-
Wissenschaft and Technologie 41: 1344-1349.
Romano, C., Abadi, K., Repetto, V., Vojnov, A.A. and
Moreno, S. 2009. Synergistic antioxidant and
antibacterial activity of rosemary plus butylated
derivatives. Food Chemistry 115: 456-461.
Nanasombat, S. and Teckchuen, N. 2009. Antimicrobial,
antioxidant and anticancer activities of Thai local
vegetables. Journal of Medicinal Plants Research
3(5): 443-449.
Noriham, A., Babji, A.S. and Aminah, A. 2005. Antioxidant
effect of plant extracts in chicken sausage. Malaysian
Journal of Animal Science 10(1): 24-27.
Ozturk, M., Ozturk, F.A., Duru, M.E. and Topcu, G.
2007. Antioxidant activity of stem and root extracts
of Rhubarb (Rheum ribes): An edible medicinal plant.
Food Chemistry 103: 623-630.
Ra, M.M. and Vastano, B.C. 2007. Identication
of a structure specic Bcl-2 phosphorylating
homoisoavone molecule from Vietnamese coriander
(Polygonum odoratum) that induces apoptosis and
G2/M cell cycle arrest in breast cancer cell lines. Food
Chemistry 104: 332-340.
Roberts, W.G. and Gordon, M.H. 2003. Determination of
the total antioxidant activity of fruits and vegetables
by a liposome assay. Journal of Agricultural and Food
Chemistry 51: 1486-1493.
Schwertner, H.A. and Rios, D.C. 2007. High-performance
liquid chromatographic analysis of 6-gingerol,
8-gingerol, 10-gingerol, and 6-shogaol in ginger
–containing dietary supplements, spices, teas, and
beverages. Journal of Chromatography B 856: 41-47.
Shan, B., Cai, Y. Z., Sun, M. and Corke, H. 2005. Antioxidant
capacity of 26 spice extracts and characterization of
their phenolic constituents. Journal of the Agricultural
and Food Chemistry 53: 7749–7759.
Sharma, R. A., Gescher, A. J. and Steward, W. P. 2005.
Curcumin: The story so far. European Journal of
Cancer 41: 1955–1968.
Singleton, V.L. and Rossi, J.A. 1965. Colorimetry of total
phenolics with phosphomolybdic-phosphotungstic
acid reagents. American Journal of Enology and
viticulture 16: 144-158.
Stoilova, I., Krastanov, A., Stoyanova, A., Denev, P. and
Gargova, S. 2007. Antioxidant activity of a ginger
extract (Zingiber ofcinale). Food Chemistry 102:
764-770.
Suhaj, M. 2006. Spice antioxidants isolation and their
antiradical activity: a review. Journal of Food
Composition and Analysis 19: 531-537.
Sun, T. and Ho, C.T. 2005. Antioxidant activities of
buckwheat extracts. Food Chemistry 90:743-749.
Tangkanakul, P., Auttaviboonkul, P., Niyomwit,
B., Lowvitoon, N., Charoenthamawat, P. and

50 Maizura, M. Aminah, A. and Wan Aida, W. M.
International Food Research Journal 18: 526-531
Trakoontivakorn, G. 2009. Antioxidant capacity, total
phenolic content and nutritional composition of Asian
foods after thermal processing. International Food
Research Journal 16: 571-580.
Vimala, S., Adenan, M.L., Ahmad, A.R. and Shahdan,
R. 2003. Nature’s choice to wellness: antioxidant
vegetables/ulam. Malaysia. Forest Research Institute.
Valko, M., Leibfritz, D., Moncola, J., Cronin, M.T.D.,
Mazura, M. and Telser, J. 2007. Free radicals and
antioxidants in normal physiological functions and
human disease. International Journal Biochemistry
Cell Biology 39: 44–84.
Wolfe, K. W. X. and Liu, R. H. 2003. Antioxidant activity
of apple peels. Journal of Agricultural and Food
Chemistry 51(3): 609–614.
Wong, C., Li, H., Cheng, K. and Chen, F. 2006. A systematic
survey of antioxidant activity of 30 Chinese medicinal
plants using the ferric reducing antioxidant power
assay. Food Chemistry 97: 705-711.
Wu, C.Q., Chen, F., Wang, X., Kim, H.J., He, G.Q., Haley-
Zitlin, V. and Huang, G. 2006. Antioxidant constituents
in feverfew (Tanacetum parthenium) extract and their
chromatographic quantication. Food Chemistry 96:
220–227.
Zheng, W. and Wang, S. 2001. Antioxidant activity and
phenolic composition in selected herbs. Journal of
Agricultural and Food Chemistry 49: 5165-5170.