Antioxidant Activity and Isolation of Luteoline from Centaurea behen L . Grown in Iran

Flavonoids are secondary metabolites providing Ultraviolet-visible (UV) spectroscopy protection and color in almost all terrestrial plants and fruits. ey have a fused ring system consisting of an aromatic ring and a benzopyran ring with a phenyl substituent. As their biological activities have an impact on human health, they serve as target molecules in the development of new drugs. e objective of this research was to study the antioxidant activity and chemical analysis of the luteoline from Centaurea behen L. (Compositae family). e aerial parts of powdered and dried C. behen were extracted with methanol (MeOH) in a Soxhlet apparatus over a period of 2 days. e concentrated total extract was extracted with petroleum ether, diethylether, and methanol. From themethanol extract of the aerial parts ofC. behen, the �avonoid derivative (luteoline) was identi�ed.e aerial parts’ extract demonstrated effective antioxidant activitymeasured in terms of half-maximal inhibitory concentration (IC50).e product extract has been isolated by UV, column chromatography (CC), and preparative high-performance liquid chromatography (HPLC). e structures involvedwere elucidated by Hand Cnuclearmagnetic resonance (NMR) and heteronuclearmultiple-bond correlation (HM�C) spectra. e compound identi�ed had not been reported in previous studies of C. behen L.


Introduction
roughout time, many plants have been used for the treatment of mental problems.A good number of these have been alkaloid-containing plants, as alkaloids are known to have a strong interaction with receptors in the central nervous system (CNS).In recent years, however, it has become clear that �avonoids may also play a role in the action of enzymes on the receptor systems of the brain, exerting various effects on the CNS, including prevention of the neurodegeneration associated with Alzheimer's and Parkinson's diseases [1].
Flavonoids possess a variety of biological activities in addition to their effects on the CNS.ey have attracted attention as free radical scavengers with antioxidant activity.ey are yellow, blue, or red and function to afford UV protection for plants and as pollination aids by providing speci�c colors or patterns to �owers.More than 6000 �avonoids have been identi�ed.
Plants in which �avonoids are thought to or have been proven to be active constituents include species with a long history of use in traditional folk medicines in Europe.For centuries chamomile �owers (Matricaria recutita L., Asteraceae family) have been used for their calming effect, which is due to their apigenin content [2].We studied the mechanism of nanocapsules of Matricaria recutita by the emulsiondiffusion process [3,4].is study showed that nanocapsules of plant extract can be effective in medicinal drugs.Other monoterpenes produced an oxidation reaction, releasing energy to fuel biological cycles [4].ere are eight species of the genus Carduus (Asteraceae family) growing wild in Iran [5,6].Previous chemical investigations on Carduus species have shown the presence of �avonoids, steroids, and triterpenoid constituents [7].e biological transformation of the natural plant product mycene by Pseudomonas aeruginosa and of citral by Aspergillus niger demonstrated hydroxylation [3,8].A report on the methanol extract of Tanacetum parthenium (Asteraceae family) from Northwest Iran identi�ed the �avonoids �avonol, kaempferol, �setin, and naringenin [9].In addition, identi�cation of the �avonoids from Zosimia absinthifolia (Umbelliferae family) and Galium verum (Rubiaceae family) is found in the literature [10,11].Our study of Salvia glutinosa (Lamiaceae family) found high �avonoid content [12].
Previous chemical investigations on Centaurea species have shown the presence of �avonoids [13]; sesquiterpene lactones, especially guaianolides [14][15][16]; germacranolidetype sesquiterpene lactones [13].Sesquiterpene lactones have been reported to have multiple bene�cial biological effects, including cytotoxic, antibacterial, anti-in�ammatory, and hypotensive.A study of �owering and aerial parts of Centaurea africana Lamk var.africana (Bonnet) M., a species endemic to Algeria and Tunisia, isolated a new acylated �avonoid glucoside [17].Other studies of Centaurea africana have reported on compounds extracted from the �owering and aerial parts [18,19].To the best of our knowledge, this is the �rst report on the �avonoids extracted from the aerial parts of C. behen L. from Iran and their antioxidant activities.

Methods
2.1.General Experimental.e IR spectra were determined on a Bruker Tensor 27 spectrometer.e 1 H NMR and 13 C NMR spectra were recorded on a Bruker AM 300 spectrometer.Column chromatography was performed over silica gel (70-230 mesh, Merck) using petroleum ether, AcOEt, and methanol gradients as eluents.UV spectra were recorded on a Perkin Elmer Lambda 12 spectrophotometer, and mass spectra were recorded on an AEI MS-50 spectrometer.

Plant Materials. e aerial parts of Centaurea behen
L. were collected in June 2009 from Givi, Khalkhal Road (Ardabil province) in the northwest of Iran, at an altitude of 1400 m.A voucher specimen (No. 1563) has been deposited at the Herbarium of the Agriculture Research Centre, Ardabil, Iran.

Extraction and Isolation. Dried and �nely powdered
Centaurea behen L. aerial parts (600 g) were treated with methanol using a Soxhlet extractor over a period of 2 days.e concentrated total extract (72 g) was extracted with petroleum ether, diethylether (Et 2 O), and methanol.A part of the Et 2 O portion (3 g) was subjected to silica gel column chromatography (70-230 mesh, Merck), eluted with an equivalent petroleum ether, diethylether, and methanol stepwise gradient to obtain 32 fractions (15 mL each).Aer the evaporation of the solvent, fractions 7-13 were chromatographed over silica gel with the Et 2 O : MeOH mixture to provide 16 subfractions.Subfraction 7 (145 mg) was rechromatographed on silica gel into 12 fractions (20 × 15 mL) using as eluents an 8.5 : 1.5 Et 2 O : MeOH mixture.e combined fractions 6 to 10 (24 mg) were further puri�ed on a preparative TLC to give compound 1 (14 mg) [20].

Antioxidant Activity Tests
2.4.1.DPPH Assay.e DPPH assay was carried out using a modi�ed form of the method used by Cheung et al. [21].In brief, 0.5 mL of 1,1-diphenyl-2-picrylhydrazyl (DPPH) in ethanol (0.1 mM) was added to 1 mL of extracts in different concentrations (50-800 g mL −1 ) and le in the dark for 10 min.e absorbance of the resulting solution was recorded on a spectrometer at 520 nm against a blank of alcohol.Vitamin C was used as the reference antioxidant.DPPH scavenging activity was expressed as IC 50 values (g extract mL −1 ) for comparison.e IC 50 value of each sample was de�ned as the concentration of sample required for a 50% decrease in absorbance of the blank [22].

Determination of Total Phenolic Compounds.
Total phenolics of the aerial parts of C. behen were determined by methods described in the literature, using the Folin-Ciocalteau reagent with gallic acid as the calibration standard (both obtained from Sigma-Aldrich).An aliquot (0.1 mL) of extract solution containing 1 mg of extract was transferred to a volumetric �ask; 46 mL of distilled water and 1 mL of Folin-Ciocalteau reagent were added, and the �ask was thoroughly shaken.Aer 3 min, 3 mL of a solution of 7% Na 2 CO 3 was added, and the mixture was allowed to stand for 2 h with intermittent shaking.Absorbance was measured at 765 nm.

Amount of DPPH.
e antioxidant activity of the compound was measured in terms of hydrogen donating or radical scavenging ability, using the stable radical DPPH.e C. behen extract was able to reduce the stable radical DPPH to the yellow-coloured diphenylpicrylhydrazine with an IC 50 value of 200 ± 7.0 g mL −1 .e concentration of the positive control Vitamin C required to scavenge 50% of the free radical T 1: HMBC connectivities for the assignment luteoline.
Step was 260 ± 8.0 g mL −1 .In this research, we used Vitamin C for measurement DPPH and compare together (Figure 3).

Total Phenol Content.
Total phenol compounds, as determined by folin Ciocalteau method, are reported as gallic acid equivalents by reference to standard curve.e plant had good total phenol contents and they may cause the antioxidative activities of the C. behen.Phenols and polyphenolic compounds, such as �avonoids, are widely found in food products derived from plant sources, and they have been shown to possess signi�cant antioxidant activities.In our investigation the highest total phenolic content was found in the C. behen.We experiment all data and replicated three times.
For this study, the aerial parts of Centaurea behen were collected from Givi, Khalkhal Road (Ardabil province) in the northwest of Iran.is plant contained �avonoid compounds and showed antioxidant activity, indicating potentially wide applications in formulation of medicinal drugs.Extracts of the aerial parts of C. behen obtained using a Soxhlet extractor were chromatographed on silica gel columns.e compound obtained was identi�ed as compound (1).e structure of the compound was established by chemical and spectral analysis, including UV and 1 H and 13 C NMR as well as by comparing their spectroscopic data with those reported in the literature.e mass spectrum presented at m/z 286 according to the molecular formula C 15 H 10 O 6 .e 1 H NMR spectrum (CDCl 3 ) showed groups at 6.98 (H-5 � ) and 10.09 (H-6 � to H-4 � ).e spectrum also showed a one-proton singlet signal at 10.09 (H-4 � ) in 1 H NMR, which may be the �avonoid skeleton.Other signals of the 13 C NMR spectrum were shown at 124 (C=), 163 (O-C=), and a doublet at dH 5.13 (  .6 H�).Signi�cant HMBC correlations were observed between H-2 � and C-4 � , and between H-3 and C-5, con�rming the location of the OH groups.e UV spectrum exhibited absorption maxima at 283 nm and 369 nm, which are characteristic absorption bands of a �avonoid skeleton as reported in the literature concerning 5,7-dihydroxy-2-(3,4-dihydroxyphenyl)-4H-chromen-4-one [29].e isolated �avonoid has a weight of 14 mg.at showed good yield for luteoline.In other research, we identi�ed a sesquiterpene with low yield [20].So in next fraction, we found glycoside luteline but we cannot separate by HPLC because that was not suitable amount.So in this plant were other �avonoids with trace small.

Antioxidant Activity.
Antioxidant activity of the compound (1) was determined by two different test systems, DPPH and total �avonoid.In the DPPH method, the antioxidants react with the stable free radical, DPPH (deep violet color), and convert it to DPPH with discoloration.e degree of discoloration indicates the free radical scavenging potentials of the sample/antioxidant.It has been found that known antioxidants such as cysteine, glutathione, ascorbic acid, and polyhydroxy aromatic compounds (hydroquinone, pyrogallol, etc.) reduce and decolorize DPPH due to their hydrogen-donating ability.Synergistic effects of phenolic acids, for example, rosmarinic acid and polyphenols as well as other chemicals such as �avonoids, could also be taken into account for the radical scavenging activity observed in the methanol extracts.e total phenolic content of C. behen extract was measured by the Folin-Ciocalteau method.Total phenol compound, as determined by the Folin-Ciocalteau method, are reported as gallic acid equivalents by reference to the standard curve.e highest total phenolic content was found in the C. behen extract [2,12,30].Figure 3 shown to stable free radical DPPH method is an easy, rapid, and sensitive way to survey the antioxidant activity of a speci�c compound or plant extracts.e capacity of plant extract to scavenge DPPH was measured and the results are shown in Figure 3. e antioxidants react with DPPH, a purplecolored stable free radical, and convert it into a colorless --diphenyl--picryl hydrazine.e amount of reduced DPPH could be quanti�ed by measuring the decrease in absorbance at 517 nm.CS extract reduced DPPH radicals in a dose-dependent manner.IC 50 of the standard compound, Vitamin C was 260 ± 8.0 g mL −1 .As can be seen in Figure 3, the extract at 72 mg mL −1 scavenged about >80% of DPPH radicals and had an IC 50 value of 59 mg mL −1 .So the extract showed potency than the controls in this study.e DPPH scavenging ability of the extract may be attributed to its hydrogen donating ability.

Conclusions
In this work we performed a chemical analysis of luteoline extracted from the aerial parts of C. behen and studied its antioxidant activity.We identi�ed the �avonoid derivative compound (1), which was isolated by UV, CC, and HPLC.e structure was elucidated by 1 H and 13 C NMR and HMBC spectra.e compound identi�ed had not been reported in our previous studies.Radical scavenging activity exhibited was determined to be IC 50 = 200 ± 7.0 g mL −1 .