Polyphenol Contents and Antioxidant Activities of Five Indigofera Species (Fabaceae) from Burkina Faso
Aqueous acetone extracts prepared from five Indigofera
species of Burkina Faso, namely Indigofera colutea (Burm.) Murril.,
I. macrocalyx Guilld et Perr., I. nigritana Hook f., I.
pulchra willd. and I. tinctoria L., were investigated for their
phytochemical composition and their antioxidant activities. Standard methods
and TLC were used to screen the phytochemical composition. The total phenolic
and flavonoid content of extracts were assessed by Folin-Ciocalteu and
AlCl3 methods, respectively. These extracts were also evaluated
for their antioxidant potentials using ferric reducing antioxidant power
(FRAP), 2,2-diphenyl-l-picrylhydrazyl (DPPH) and 2,2`-azinobis(3-ethylbenzothiazoline-6-sulphonate)
(ABTS) assays. Flavonoids, saponins, quinones, sterols/triterpenes and
tannins were present in all these species except for I. pulchra
where quinones were not found. Gallic acid, caffeic acid, rutin and myricetin
in I. colutea; gallic acid, quercitrin, myricetin in I. tinctoria;
galangin and myricetin in I. macrocalyx were identified
by thin layer chromatography. Among these, I. colutea, I.
tinctoria, I. nigritana and I. macrocalyx, which had
the highest phenolic content, were also found to possess the best antioxidant
activities. The results indicated a good correlation between antioxidant
activities and total phenolic content (p<0.05 for FRAP/DPPH and DPPH/ABTS
and p<0.01 for FRAP/ABTS). These plants represent promising sources
of natural antioxidants and these findings give scientific bases to their
The genus Indigofera comprises around 700 species that are
distributed geographically in tropical regions. In Burkina Faso, Nigeria
and India, Indigofera colutea (Burm.) Murril., I. macrocalyx
Guilld et Perr., I. nigritana Hook f., I. pulchra willd.
and I. tinctoria L. have intensive popular use in the treatment
of malaria, dysentery, constipation, stomach ache, fatigue, skin disease
and wounds (Table 1).
Rotenoids isolated from I. tintoria were found to be toxic to
larvae of Anopheles stephensi and adults of Callosobruchus chinensis
(Kamal and Mangla, 1993).
||Medicinal uses of Indigofera species
Recently, antidyslipidemic activity (Narender et al., 2006) and
hepatoprotective effects (Singh et al., 2006) of I. tinctoria
have been reported. Except these data, little is known on the biological
properties of Indigofera species despite their intensive uses by
local inhabitants in West Africa and India. Therefore, investigation on
the biological properties of Indigofera species is needed for their
safe and efficient use.
Among the biological potential of medicinal plants, the antioxidant activity
has gained an increase interest these last years because of the role that
they play in the prevention of chronic ailments such as heart disease,
cancer, diabetes, hypertension, stroke and Alzheimer`s disease by combating
oxidative stress (Cole et al., 2005; Liu, 2003; Riboli and Norat,
According to some researchers, vitamins, phenolic and carotenoids are
the major natural antioxidant groups (Rice-Evans et al., 1997;
Gülçin, 2006; Thaipong et al., 2006). Phenolic compounds
are secondary metabolites widespread in the plant kingdom and which differ
widely in terms of structure and biological properties.
The aim of the present study was to examine the total phenolic and flavonoid
contents as well as the antioxidant activity of five Indigofera aqueous
acetone extracts. The antioxidant potential has been determined using
ferric reducing antioxidant power assay (FRAP), 2,2-diphenyl-1-picrylhydrazyl
(DPPH) free radical and the 2,2-azinobis-(3- ethylbenzthiazoline-6-sulphonic
acid) (ABTS) free radical scavenging assays.
MATERIALS AND METHODS
Chemicals: The Folin-Ciocalteu reagent, NaH2PO4,
Na2HPO4, sodium carbonate, aluminium trichloride
(AlCl3), diphenylboric acid 2-aminoethyl Ester (diphenyl- boryloxyethylamine),
gallic acid and quercetin were purchased from Sigma aldrich chemie, Steinheim,
Germany. 2,2-diphenyl-l-picrylhydrazyl (DPPH); 2,2`-azinobis(3-ethylbenzothiazoline-6-sulphonate)
ABTS, polyethylene glycol 4000, trichloroacetic acid, potassium persulfate
and solvents used were from Fluka Chemie, Buchs, Switzerland. Potassium
hexacyanoferrate [K3Fe(CN)6] was from Prolabo, Paris,
France and ascorbic acid was from Labosi, Paris, France. All chemicals
used were of analytical grade.
Plant material: Indigofera colutea (Burm.) Murril., I.
macrocalyx Guilld et Perr., I. nigritana Hook f., I.
pulchra willd. and I. tinctoria L. were collected in the Ouagadougou
region of Burkina Faso in August 2005 and identified by Pr. J. Millogo,
a botanist from the University of Ouagadougou. Voucher specimen numbers
01, 02, 03, 04 and 05, (respectively for I. colutea, I. marcrocalyx,
I. nigritana, I. pulchra and I. tinctoria) were deposited
in the Herbarium of Laboratoire de Biologie et d`Ecologie Végétales
UFR/SVT University of Ouagadougou.
Preparation of plant extracts: For each plant, the freshly cut stems with leaves were dried at
room temperature and ground to fine powder using a grinder. The extraction
was processed using 50 g of powder in 500 mL of acetone:water (80:20)
during 48 h under mechanical agitation (SM 25, Edmund BÜHLER, Germany,
shaker), at room temperature. After filtration, acetone was removed under
reduced pressure in a rotary evaporator (BÜCHI Rotavapor R-200, Switzerland)
and the remaining aqueous solutions were lyophilised using a freeze drying
system (Cryodos 50, TELSTAR, Spain).
Phytochemical screening and thin-layer chromatography (TLC): The aqueous acetone extract obtained from each plant was used to screen alkaloids, tannins, anthraquinones, flavonoids, saponins, triterpenoids,
steroids and coumarins using the method described by Ciulei (1982). The
thin layer chromatography analysis of phenolic acids and flavonoids were
performed according to Medié-Sarié et al. (2004)
and Wagner and Bladts (1996) methods.
The thin layer chromatography plates (Silica gel 60F254, Kiesel
gel, 10x10 cm) were spotted with standards or plant extracts and developed
in solvent system S1 (Ethyl acetate:formic acid:glacial acetic acid:water,
100:11:11:26) or S2 (n-hexane:ethyl acetate:acetic acid, 62:24:10). Phenolic
acids and flavonoids were revealed by spraying the plate with NEU-reagent
(Natural products-polyethylene glycol reagent).
Determination of total phenolic and total flavonoid contents: Total phenolic content of each plant extract was determined by Folin-Ciocalteu method (Singleton et al., 1999). The diluted aqueous solution of
each extract (0.5 mL) at a concentration of 100 μg mL-1
was mixed with 2.5 mL of Folin Ciocalteu reagent (0.2 N). This mixture
was allowed to stand at room temperature for 5 min and then, 2 mL of sodium
carbonate solution (75 g L-1 in water) was added. After 2 h
of incubation, the absorbencies were measured at 760 nm against a water
blank using a spectrophotometer (CECIL CE 2041, CECIL Instruments, England).
The standard calibration curve was plotted using gallic acid (0-200 mg
L-1). The determination was performed in triplicate and the
results were expressed as mg of Gallic Acid Equivalents (GAE)/100 mg of
The total flavonoid content of the plant extract was estimated according
to Dowd method, as adapted by Arvouet-Grand et al. (1994). For
each extract, 2 mL of methanolic solution (100 μg mL-1)
was mixed with 2 mL of aluminium trichloride (AlCl3) in methanol
(2%). The absorbance was read at 415 nm after 10 min against a blank sample
consisting of a 2 mL of methanol and 2 mL of plant extract without AlCl3.
Quercetin was used as reference compound to produce the standard curve
and the average of three readings was used and expressed as mg of Quercetin
Equivalents (QE)/100 mg of plant extract.
Iron (III) to iron (II) reduction activity (FRAP): The total antioxidant capacity of plant extract was determined using
iron (III) reduction method (Hinneburg et al., 2006). The diluted
aqueous solution of each extract (1 mL) at a concentration of 100 μg
mL-1 was mixed with 2.5 mL of phosphate buffer (0.2 M, pH 6.6)
and 2.5 mL of a 1% aqueous potassium hexacyanoferrate [K3Fe(CN)6]
solution. After 30 min incubation at 50°C, 2.5 mL of trichloroacetic
acid (10 %) was added and the mixture was centrifuged at 3000 rpm for
10 min. Then, 2.5 mL of the upper layer solution was mixed with 2.5 mL
of water and 0.5 mL of an aqueous FeCl3 (0.1%) solution. Absorbencies
were read at 700 nm and ascorbic acid was used to produce the calibration
curve. The iron (III) reducing activity determination was performed in
triplicate and expressed in mmol Ascorbic Acid Equivalents per gram of
DPPH radical method: The ability of the extract to scavenge DPPH (2, 2-diphenyl-1-picrylhydrazyl)
radical was determined according to the method of Velazquez et al.
(2003) with some modifications. Briefly, 1.5 mL of a freshly prepared
methanolic solution of DPPH (20 mg L-1) was mixed with 0.75
mL of extract solution (0.003-1 mg mL-1). After 15 min of incubation
in the dark, at room temperature, absorbencies were read at 517 nm against
a blank sample consisting of a 1.5 mL of methanol and 0.75 mL of extract
Quercetin, ascorbic acid and gallic acid were used as positive controls.
All determinations were performed in triplicate. DPPH radical inhibition
percentage was calculated according to the formula of Miliauskas et
Inhibition (%) = [(AB-AA)/AB]x100
where, AB is the blank absorbance and AA the sample
absorbance (tested extract solution), IC50 value was obtained
by graphically determination. A lower IC50 value indicates
greater antioxidant activity.
ABTS radical cation decolorization assay: The radical scavenging capacity of antioxidants for ABTS radical
cation was carried out as described by Re et al. (1999). The ABTS+
was generated by reacting 7 mM aqueous solution of ABTS with 2.5 mM potassium
persulfate (final concentration) followed by storage in the dark, at room
temperature, for 12 h before use. The mixture was diluted with ethanol
to give an absorbance of 0.70±0.02 unit at 734 using spectrophotometer.
For each extract, a 20 mg mL-1 solution in methanol was prepared
and further 100 fold diluted in ethanol. Ten microliter of this diluted
sample was allowed to react with 990 μL of fresh ABTS+
solution and then absorbance was taken 6 min exactly after initial mixing.
Ascorbic acid was used as standard and the capacity of free radical scavenging
was expressed as mmol ascorbic acid equivalents g-1 of extract.
Statistical analysis: For statistical analysis, MS Excel software (CORREL Statistical
function) was used to calculate quercetin, ascorbic acid and gallic acid
equivalents, to determine inhibition percentage and to establish linear
regression equations. Pearson Product Moment function and One way ANOVA
(Tukey test) of SigmaStat 2.0 (Jandel Scientific software) were used to
determine correlation coefficients (R) and the level of statistical significance,
RESULTS AND DISCUSSION
Different Indigofera species from Burkina Faso folk medicine
have been studies, in order to support and confirm their uses (Table
Firstly, aqueous acetone extracts prepared from studied plants were screened
for their phytochemical composition. The dry residues obtained were 5.57
g for I. colutea, 6.02 g for I. macrocalyx, 5.96 g for I.
nigritana, 5.28 g for I. pulchra and 12.63 g for I. tinctoria.
Flavonoids, saponins, quinones, sterols/triterpenes and tannins were
detected in all these species with an exception being the absence of quinones
in I. pulchra (Table 2). The presence of saponin,
flavonoid and tannin in some Indigofera species such as I.
arrecta, I. aspalathoides and I. dendroides has already
been reported (Christina et al., 2003; Esimone et al., 1999;
Contrasting with the findings of a previous study on a close related
species (Leite et al., 2006), namely I. suffruticosa, alkaloids
and coumarins were not detected in the plants used in this study.
Further confirmation for the presence of phenolic compounds was made
by thin layer chromatography.
||Phytochemical screening of acetone extract of Indigofera
||Polyphenol contents and antioxidant activities of Indigofera
|Results are mean±SD (n = 3), Values with the
same letter(s) are not significantly different (p>0.05)
Galangin in I. macrocalyx extract, gallic and caffeic acids in
I. tinctoria and gallic acid in I. colutea were identified
using the solvent system 2. With the system 1, rutin in I. pulchra,
rutin and myricetin in I. tinctoria, quercitrin and myricetin in
I. pulchra and myricetin in I. macrocalyx were identified
The result shows a qualitative difference in phenolic acids and flavonoids
composition between these species. As the detected phenolics have different
known biological activities, their presence can partially justify some
of the medicinal uses of Indigofera species in Burkina Faso. Examples
are the anti-inflammatory and antimicrobial activities of galangin, rutin
and gallic acid (Bruneton, 1993; Carnat et al., 2004; Elliott et
al., 2000; Rajkapoor et al., 2004; Raj Narayana et al.,
2001; Ueda et al., 2002) which can justify the uses of these Indigofera
species to cure inflammation and skin diseases.
Because the structure of phenolic compounds, mainly the position of the
hydroxyl radical, plays a major role in their antioxidant properties (Miliauskas
et al., 2004), these five Indigofera species were studied,
keeping in mind the difference in their qualitative composition. For this
purpose, the total phenolic and flavonoid content of the different extracts
Total phenolic and flavonoid content estimated from the calibration curves
(Y = 104.83 X, R2 = 0.9969 for total phenolic and Y= 40.23
X, R2 = 0.9999 for total flavonoid content) are shown in Table
3. The highest total phenolic content was recorded in I. colutea
extract (54.27±4.87 mg GAE/100 mg) while the highest amount
of flavonoids (9.63±0.45 mg QE/100 mg of dried extract) was found
in the extract of I. nigritana.
High levels of phenolic were also found in I. nigritana and
I. tinctoria and the lowest flavonoid content which found in I.
colutea and I. tinctoria. These results showed that I. macrocalyx
and I. nigritana have comparable amounts of total phenolic
and total flavonoid. No significant correlation was found between the
total phenolic and the total flavonoid content.
The FRAP assay determined the reducing power of plant extracts resulting
from the ability of their components to donate electrons and, therefore,
participate in redox reactions. Using the standard curve of ascorbic acid
(Y = 126.9X, R2 = 0.9999), the best activities were found with
I. colutea (2.54± 0.14 mmol g-1)
and I. tinctoria (2.04±0.09 mmol g-1) extract
followed by I. nigritana (1.57±0.06 mmol g-1)
and I. macrocalyx (1.41±0.02 mmol g-1) (Table
3). For these four plants, the amounts of ascorbic acid equivalents
were significantly higher than that of I. pulchra (0.81±0.01
The DPPH assay is based on the measurement of the relative inhibition
of the extract tested at various concentrations. Chemicals which are able
to change the colour of the DPPH free radical from violet to yellow can
be considered as antioxidants and therefore, radical scavengers (Hinneburg
et al., 2006). Table 3 shows that values of the
50% inhibition concentration (IC50) varied from 2.45 0.15 to
12.37 0.32 μg mL-1.
The best antioxidant activity was obtained from I. colutea (2.45
± 0.15 μg mL-1) followed by I. nigritana (3.68±0.87
μg mL-1) and I. tinctoria (3.79±0.08 μg
mL-1), which with the first one, were also found to possess
the highest phenolic content. I. pulchra with low phenolic content
exhibited a relatively weak antioxidant activity. The IC50
values for the references were 1.80±0.43 μg mL-1
for ascorbic acid, 0.88±0.11 μg mL-1 for quercetin
and 0.61±0.14 μg mL-1 for gallic acid.
These data show that all these extracts displayed significant antioxidant
activity (IC50 <15 μg mL-1), but the reference
substances were more radical scavengers than the Indigofera extracts.
The free radical scavenging ability of Indigofera species was
also determined using ABTS radical cation. Ascorbic acid was used to produce
the dose response curve.
Table 3 shows ascorbic acid equivalents antioxidant
capacity of the different extracts in ABTS assay which were estimated
from the standard curve of ascorbic acid (Y = 20.06-33.48X, R2
The strongest antioxidant activities were obtained from I. colutea
(3.74±0.14 mmol g-1) and I. tinctoria (3.00±0.37
mmol g-1) which possess the highest phenolic content. I.
pulchra with a low phenolic content has shown the weakest antioxidant
capacity (1.36±0.25 mmol g-1).
In this study, ascorbic acid has been used as standard instead of trolox,
because these two chemicals have almost the same inhibition percentage
at 734 nm for ABTS radical cation (Katalinic et al., 2006). Several
study confirm the usefulness of ascorbic acid (Lee et al., 2003;
Soong and Barlow, 2004).
In the present study, the highest phenolic content and the best antioxidant
activities, using 3 different methods, were recorded in I. colutea.
These results suggest that it can be a good source of antioxidants.
The antioxidant activities of these different Indigofera species
can be attributed, in part, to their gallic acid, rutin and myricetin
content, due to the strong antioxidant capacity of these chemicals. The
high total phenolic content of these plants can also explain, in part,
these good antioxidant activities. This last assertion is strongly supported
by the correlation studies (Fig. 1) which show good correlations
between the total phenolic content and iron reduction (R = 0.95, p<0.05),
DPPH inhibition (R = 0.99, p<0.001) and ABTS reduction (R = 0.92, p<0.05).
Otherwise, more than 90% of the antioxidant capacity of these plant extracts
derives from the contribution of phenolic compounds and the antioxidant
activity is not limited to phenolics. The activity may also come from
the presence of other antioxidant compounds which, in this case, are contributing
for 9% of the antioxidant capacity (Javanmardi et al., 2003).
These correlations also suggest that phenolic compounds contribute well
to the antioxidant capacity of the Indigofera species. Similar
correlation were also found
with plant extracts, honey and fruits in earlier study confirming the
interest of polyphenols as natural antioxidant from plants and foods (Cai
et al., 2006; Ivanova et al., 2005; Lee et al., 2003;
Meda et al., 2005; Sawadogo et al., 2006; Zheng and Wang,
2001). This antioxidant capacity is mainly due to their redox properties,
which allow them to act as reducing agents, hydrogen donors and singlet
oxygen quenchers (Javanmardi et al., 2003).
In contrast to the total phenolic content, no significant correlation
was found between total flavonoid content and the antioxidant capacities.
A strong correlation have been found between the different antioxidant
assays (R = 0.95, p<0.05 for FRAP/ DPPH and DPPH/ABTS and R = 0.98,
p<0.01 for FRAP/ ABTS).
The good antioxidant activities of the studied plants can also justify
their uses for the treatment of inflammation, as the anti-inflammatory
properties of some polyphenols derive mainly from their free radical scavenging
activities (Fenglin et al., 2004). Nevertheless, further investigations
are required to confirm this hypothesis.
This study has shown that Indigofera species, used in folk medicine
in Burkina Faso, have some phytochemicals with known pharmacological activities.
The aqueous acetone extracts of I. colutea, I. tinctoria and
I. nigritana which had the highest total phenolic content were
found to possess the strongest radical scavengers in both DPPH and ABTS
assays and also, the best reduction power in FRAP assay. Good correlations
were obtained between DPPH, FRAP and ABTS antioxidant assays and also
between each of these assays and the total phenolic content. According
to the total phenolic content and antioxidant activities of their extracts,
the plants used in this study represent a good source of antioxidant.
These results give further support to the therapeutical uses of these
We are grateful to the International Atomic Energy Agency for providing
the facilities through the technical cooperation project BKF 5002.
Abubakar, M.S., E. Balogun, E.M. Abdurahman, A.J. Nok, M. Shok, A. Mohammed and M. Garba, 2006.
Ethnomedical treatment of poisonous snakebites: Plant extract neutralized Naja nigricollis
venom. Pharm. Biol., 44: 343-348.Direct Link |
Arvouet-Grand, A., B. Vennat, A. Pourrat and P. Legret, 1994.
[Standardization of propolis extract and identification of principal constituents]. J. Pharm. Belg., 49: 462-468, (In French).PubMed | Direct Link |
Bruneton, J., 1993.
Pharmacognosie: Phytochimie-Plantes Medicinales. 2nd Edn., Tec. et Doc. Lavoisier, Paris
Cai, Y.Z., M. Sun, J. Xing, Q. Luo and H. Corke, 2006.
Structure-radical scavenging activity relationships of phenolic compounds from traditional Chinese medicinal plants. Life Sci., 78: 2872-2888.PubMed |
Carnat, A., A.P. Carnat, D. Fraisse, L. Ricoux and J.L. Lamaison, 2004.
The aromatic and polyphenolic composition of Roman camomile tea. Fitoterapia, 75: 32-38.CrossRef | Direct Link |
Christina, A.J.M., M.A. Jose, S.J.H. Robert, R. Kothai, N. Chidambaranathan and P. Muthuman, 2003.
Effet of Indigofera aspalathoides
against Dalton’s ascitic lymphoma. Fitoterapia, 74: 280-283.CrossRef |
Ciulei, I., 1982.
Practical Manuals on the Industrial Utilization of Chemical and Aromatic Plants. Methodology for Analysis of Vegetable Drugs. 1st Edn., Ministry of Chemical Industry, Bucharest, pp: 67
Cole, G.M., G.P. Lim, F. Yang, B. Teter and A. Begum et al
Prevention of Alzheimer's disease: Omega-3 fatty acid and phenolic anti-oxidant interventions. Neurobiol. Aging, 26: 133-136.CrossRef |
Middleton, Jr. E., C. Kandaswami and T.C. Theoharides, 2000.
The effects of plant flavonoids on mammalian cells: Implications for inflammation, heart disease and cancer. Pharmacol. Rev., 52: 673-751.PubMed | Direct Link |
Esimone, C.O., M.U. Adikwu and K.N. Muko, 1999.
Antimicrobial properties of Indigofera dendroides
leaves. Fitoterapia, 70: 517-520.CrossRef |
Fenglin, H., L. Ruili, H. Bao and M. Liang, 2004.
Free radical scavenging activity of extracts prepared from fresh leaves of selected Chinese medicinal plants. Fitoterapia, 75: 14-23.CrossRef |
Gulcin, I., 2006.
Antioxidant activity of caffeic acid (3,4-dihydroxycinnamic acid). Toxicology, 217: 213-220.CrossRef | Direct Link |
Hinneburg, I., H.J.D. Dorman and R. Hiltunen, 2006.
Antioxidant activities of extracts from selected culinary herbs and spices. Food Chem., 97: 122-129.CrossRef | Direct Link |
Ivanova, D., D. Gerova, T. Chervenkov and T. Yankova, 2005.
Polyphenols and antioxidant capacity of Bulgarian medicinal plants. J. Ethnopharmacol., 96: 145-150.CrossRef | PubMed | Direct Link |
Javanmardi, J., C. Stushnoff, E. Locke and J.M. Vivanco, 2003.
Antioxidant activity and total phenolic content of Iranian Ocimum
accessions. Food Chem., 83: 547-550.CrossRef | Direct Link |
Kamal, R. and M. Mangla, 1993. In vivo
and in vitro
investigations on rotenoids from Indigofera tinctoria
and their bioefficacy against the larvae of Anopheles stephensi
and adults of Collosobruchus chinensis
. J. Biosci., 18: 93-101.
Katalinic, V., M. Milos, T. Kulisic and M. Jukic, 2006.
Screening of 70 medicinal plant extracts for antioxidant capacity and total phenols. Food Chem., 94: 550-557.CrossRef | Direct Link |
Kerharo, J. and J.G. Adam, 1974.
La Pharmacopée Sénégalaise Traditionnelle: Plantes Médicinales et Toxiques. 1st Edn., Vigot Frères, Paris, ISBN: 2-7114–0646-6
Lee, K.W., Y.J. Kim, H.J. Lee and C.Y. Lee, 2003.
Cocoa has more phenolic phytochemicals and a higher antioxidant capacity than teas and red wine. J. Agric. Food Chem., 51: 7292-7295.CrossRef | PubMed | Direct Link |
Leite, S.P., J.R.C. Vieira, P. Lys de Medeiros, R.M.P. Leite, V.L.M Lima, H.S. Xavier and E.O. Lima, 2006.
Antimicrobial activity of Indigofera suffruticosa
. Evid. Based Complement. Alt. Med., 3: 261-265.CrossRef | Direct Link |
Liu, R.H., 2003.
Health benefits of fruit and vegetables are from additive and synergistic combinations of phytochemicals. Am. J. Clin. Nutr., 78: 517S-520S.CrossRef | PubMed | Direct Link |
Meda, A., C.E. Lamien, M. Romito, J. Millogo and O.G. Nacoulma, 2005.
Determination of the total phenolic, flavonoid and proline contents in Burkina Fasan honey, as well as their radical scavenging activity. Food Chem., 91: 571-577.CrossRef |
Medic-Saric, M., I. Jasprica, A. Smolcié-Bubalo and A. Mornar, 2004.
Optimization of chromatographic conditions in thin layer chromatography of flavonoids and phenolic acids. Croat. Chem. Acta, 77: 361-366.Direct Link |
Miliauskas, G., P.R. Venskutonis and T.A. van Beek, 2004.
Screening of radical scavenging activity of some medicinal and aromatic plant extracts. Food Chem., 85: 231-237.CrossRef | Direct Link |
Nacoulma, O.G., 1996.
Plantes médicinales et Pratiques médicinales Traditionnelles au Burkina Faso: Cas du plateau central T1 and T2. Ph.D Thesis, d’Etat ès Sciences Nat. Université de Ouagadougou
Narender, T., T. Khaliq, A. Puri and R. Chander, 2006.
Antidyslipidemic activity of furano-flavonoids isolated from Indigofera tinctoria
. Bioorg. Med. Chem. Lett., 16: 3411-3414.CrossRef | Direct Link |
Samy, R.P., S. Ignacimuthu and A. Sen, 1998.
Screening of 34 Indian medicinal plants for antibacterial properties. J. Ethnopharmacol., 62: 173-181.CrossRef | PubMed | Direct Link |
Rajkapoor, B., B. Jayakar and N. Murugesh, 2004.
Antitumor activity of Indigofera aspalathoides
on Ehrlich ascites carcinoma in mice. Ind. J. Pharmacol., 36: 38-40.Direct Link |
Narayana, K.R., M.S. Reddy, M.R. Chaluvadi and D.R. Krishna, 2001.
Bioflavonoids classification, pharmacological, biochemical effects and therapeutic potential. Indian J. Pharmacol., 33: 2-16.Direct Link |
Re, R., N. Pellegrini, A. Proteggente, A. Pannala, M. Yang and C. Rice-Evans, 1999.
Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free Radical Biol. Med., 26: 1231-1237.CrossRef | Direct Link |
Riboli, E. and T. Norat, 2003.
Epidemiologic evidence of the protective effect of fruit and vegetables on cancer risk. Am. J. Clin. Nutr., 78: 559S-569S.Direct Link |
Record, I.R., J.K. McInerney and I.E. Dreosti, 1996.
Black tea, green tea and tea polyphenols. Effects on trace element status in weanling rats. Biol. Trace Elem. Res., 53: 27-43.CrossRef | Direct Link |
Sawadogo, W.R., A. Meda, C.E. Lamien, M. Kiendrebeogo, I.P. Guissou and O.G. Nacoulma, 2006.
Phenolic content and antioxidant activity of six acanthaceae from Burkina Faso. J. Biol. Sci., 6: 249-252.CrossRef | Direct Link |
Singh, B., B.K. Chandan, N. Sharma, V. Bhardawaj, N.K. Satti, V.N. Gupta, B.D. Gupta, K.A. Suri and O.P. Suri, 2006.
Isolation, structure elucidation and in vivo
hepatoprotective potential of trans-tetracos-15-enoic acid from Indigofera tinctoria
Linn. Phytother. Res., 20: 831-839.PubMed | Direct Link |
Singleton, V.L., R. Orthofer and R.M. Lamuela-Raventos, 1999.
Analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. Methods Enzymol., 299: 152-178.CrossRef | Direct Link |
Soong, Y.Y. and P.J. Barlow, 2004.
Antioxidant activity and phenolic content of selected fruit seeds. Food Chem., 88: 411-417.CrossRef | Direct Link |
Thaipong, K., U. Boonprakob, K. Crosby, L. Cisneros-Zevallos and D.H. Byrne, 2006.
Comparison of ABTS, DPPH, FRAP and ORAC assays for estimating antioxidant activity from guava fruit extracts. J. Food Compos. Anal., 19: 669-675.CrossRef | Direct Link |
Ueda, H., C. Yamazaki and M. Yamazaki, 2002.
Luteolin as an anti-inflammatory and anti-allergic constituent of Perilla frutescens
. Biol. Pharm. Bull., 25: 1197-1202.Direct Link |
Velazquez, E., H.A. Tournier, P.M. de Buschiazzo, G. Saavedra and G.R. Schinella, 2003.
Antioxidant activity of Paraguayan plant extracts. Fitoterapia, 74: 91-97.CrossRef | Direct Link |
Zheng, W. and S.Y. Wang, 2001.
Antioxidant activity and phenolic compounds in selected herbs. J. Agric. Food Chem., 49: 5165-5170.CrossRef | PubMed | Direct Link |
Wagner, H. and S. Bladt, 1996.
Plant Drug Analysis: A Thin Layer Chromatography. 2nd Edn., Springer-Verlag, New York, USA., ISBN-13: 9783540586760, Pages: 384