Prenylated and Geranylated Flavonoids Increase Production of

Article pubs.acs.org/jnp

Prenylated and Geranylated Flavonoids Increase Production of Reactive Oxygen Species in Mouse Macrophages but Inhibit the Inflammatory Response Jan Hošek,*,† Alice Toniolo,‡ Ondřej Neuwirth,† and Chiara Bolego‡ †

Department of Natural Drugs, Faculty of Pharmacy, University of Veterinary and Pharmaceutical Sciences Brno, Palackého tř. 1/3, CZ 612 42, Brno, Czech Republic ‡ Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Largo E. Meneghetti 2, I 35131, Padua, Italy ABSTRACT: In this study, four prenylated and geranylated flavonoids, cudraflavone B (1), pomiferin (2), osajin (3), and diplacone (4), were tested for their antioxidant and antiinflammatory effects and to identify any potential relationships between chemical structure and antioxidant or anti-inflammatory properties. The selected flavonoids were examined in cellfree models to prove their ability to scavenge superoxide radicals, hydrogen peroxide, and hypochlorous acid. Further, the ability of the flavonoids to influence the formation of reactive oxygen species in the murine macrophage cell line J774.A1 was tested in the presence and absence of lipopolysaccharide (LPS). The ability of flavonoids to inhibit LPS-induced IκB-α degradation and COX-2 expression was used as a model for the inflammatory response. The present results indicated that the antioxidant activity was dependent on the chemical structure, where the catechol moiety is especially crucial for this effect. The most potent antioxidant activities in cell-free models were observed for diplacone (4), whereas cudraflavone B (1) and osajin (3) showed a pro-oxidant effect in J774.A1 cells. All flavonoids tested were able to inhibit IκB-α degradation, but only diplacone (4) also down-regulated COX-2 expression. t is well known that the intake of flavonoids (and of many other natural polyphenols) is associated with a lower risk of oxidative-stress-related diseases such as cardiovascular diseases and cancer.1,2 However, it should be noted that some flavonoids also induce pro-oxidant effects, which may account for their beneficial effects.3−5 Flavonoids are also very often studied for their anti-inflammatory properties.6 On the other hand, the antioxidant activity of flavonoids can be dissociated from their anti-inflammatory actions, probably because of contributions of different moieties of the molecule.7 Higher oxidative stress very often results in inflammation. The contribution of reactive oxygen species (ROS) to the activation of the nuclear factor (NF)-κB pathway is well known.8,9 NF-κB is a transcription factor that regulates the expression of inductors and effectors in many steps of the wide network defining the immune response to a pathogenic stimulation. In addition to the described modulation of the inflammatory response, this factor is also involved in the regulation of apoptosis and can be connected with the development of cancer.10,11 On the other hand, a low oxidative stress activates the nuclear factor erythroid 2-related factor 2 (NRF-2). The transcription factor NFR-2 triggers transcription of hundreds of genes, including antioxidant genes, e.g., heme oxygenase 1 (HO-1).12 The antioxidant action of NRF-2 leads to attenuation of the lipopolysaccharide (LPS)-induced inflammatory response.13

I

© 2013 American Chemical Society and American Society of Pharmacognosy

Bacterial LPS is a well-established NF-κB inducer. This unit of the cell walls of Gram-negative bacteria directly activates the NF-κB pathway and simultaneously induces the production of ROS, as described in a review by Gloire et al.14 Thus, LPS represents a widely used model for the inflammatory response and oxidative stress. This work was focused on four flavonoids, three prenylated and one geranylated, cudraflavone B (1, a flavone), pomiferin (2, an isoflavone), osajin (3, an isoflavone), and diplacone (4, a flavanone). Previous experiments have indicated an antiinflammatory effect of cudraflavone B (1),15 but this compound lacks antioxidant activity.16 On the other hand, diplacone (4) showed strong antioxidant, cytoprotective,17,18 and immunomodulating activities.19 In the case of two structurally very similar isoflavones (2 and 3), it has been demonstrated that pomiferin (2) is a potent antioxidant, while osajin (3) has almost no activity.20,21 The aim of this study was to determine the potential relationships between the chemical structure and the antioxidant or anti-inflammatory properties of these four flavonoids. Received: March 22, 2013 Published: August 16, 2013 1586

dx.doi.org/10.1021/np400242e | J. Nat. Prod. 2013, 76, 1586−1591

Journal of Natural Products

Article

The ability of the test flavonoids to generate ROS in J774A.1 cells was measured in a short-term (30 min) culture experiment. Compounds 2−4 slightly increased the levels of ROS by a factor of 0.95 to 1.67 compared with unstimulated cells (Figure 1), whereas compound 1 augmented the amount

■

RESULTS AND DISCUSSION Four flavonoids were tested for their scavenging activity against three reactive oxygen species (O2•−, H2O2, and HClO) (Table 1). Diplacone (4) showed the highest level of scavenging

Figure 1. Effect of flavonoids on short-term (30 min) production of ROS. J774A.1 cells were incubated with cudraflavone B (1), pomiferin (2), osajin (3), diplacone (4) (1.25 or 0.25 μM; concentrations are indicated below the graph), LPS (1 μg/mL), or only the vehicle [dimethyl sulfoxide (DMSO)]. After 30 min, the production of ROS was measured. The results are expressed as means ± SE for four independent experiments. (* indicates a significant difference (p < 0.05) in comparison to cells treated only with the vehicle. The dashed line indicates the basal level of ROS production in J774.A1 cells. )

•−

Table 1. O2 , H2O2, and HClO Scavenging Activity of Test Flavonoids (IC50, mean ± SE) IC50 (μM)

a

compound

O2•−

H2O2

HClO

cudraflavone B (1) pomiferin (2) osajin (3) diplacone (4)

219.0 ± 15.0 73.3 ± 4.8 >1000a 41.2 ± 3.7

641.2 ± 31.4 899.3 ± 40.1 >1000b 554.0 ± 45.8

1.8 ± 0.1 9.1 ± 0.2 31.0 ± 1.7 2.3 ± 0.1

of ROS significantly (3.12-fold at a concentration of 1.25 μM and 2.13-fold at 0.25 μM). The effects of these flavonoids on the generation of ROS were found to be concentrationdependent. The pro-oxidant effect of natural flavonoids has been well described for catechins, especially for (−)-epigallocatechin-3-gallate (EGCG), isolated from green tea leaves.22 According to this new research line, our group has also demonstrated that a short-term exposure of HUVEC (human umbilical vein endothelial cells) to EGCG increases the production of ROS,24 whereas a long-term incubation is associated with antioxidant properties (unpublished data). Some other flavonoids, e.g., fisetin, also show pro-oxidant activity.23 The high pro-oxidant potential of 1 could account partially for its low antioxidant activity, as determined in cellfree models. Interestingly, compound 3, which shows a markedly less potent antioxidant effect than 1, exhibited a very low production of ROS in the cell culture during a shortterm (30 min) exposure. This could result from the presence of only one hydroxy group on the B-ring. The pro-oxidant features of natural flavonoids are often connected with their potential anticancer action.3,22 The next experiment was focused on the ability of the test flavonoids to affect the generation of ROS in LPS-activated macrophages after a 24 h exposure. Bacterial LPS induces the production of ROS in immune cells via NADPH oxidase (NOX)-425 and thus participates in the activation of NF-κB.9,14 The presence of LPS in the culture medium significantly increased the level of ROS in J774A.1 macrophages (Figure 2). Co-incubation of the cells with LPS and 4 had no effect on the production of ROS, and co-incubation with 2 reduced the level of ROS only slightly. On the other hand, at a concentration of 1.25 μM, 1 and 3 significantly increased the production of ROS

39% scavenging activity at 1 mM. b17% scavenging activity at 1 mM.

activity against superoxide radicals and hydrogen peroxide with IC50 values of 41.2 ± 3.7 and 554.0 ± 45.8 μM, respectively. As described previously, 4 exhibited the most potent DPPH antioxidant activity of the compounds isolated from Paulownia tomentosa (Thunb.) Steud. (Paulowniaceae) fruits.17 Zima et al. tested geranylated flavonoids obtained from this same plant and found 4 to be one of the most effective scavenging agents against superoxide, hydroxyl, ABTS, and DPPH radicals.18 The antioxidant effect of 4 corresponds to two hydroxyl group substituents, present at positions C-3′ and C-4′ on the B-ring, which is one of the most important criteria for antioxidant activity.2 A similar catechol moiety on the B-ring is found in pomiferin (2), which also showed good antioxidant activity against superoxide radicals. However, translocation of the Bring from C-2 to C-3 reduces the resultant antioxidant activity. Of the isoflavonoids tested, 2 was a more potent scavenger than 3, with an IC50 value of 9.1 ± 0.2 μM for 2 and 31.0 ± 1.7 μM for 3 in the case of the HClO assay. This could be caused by a greater number of hydroxyl group substituents on the B-ring. This is consistent with the studies of Veselá et al. and Diopan et al., where 3 showed little or no antioxidant activity.20,21 Compound 3 exhibited O2•−-scavenging activity of 39% and H 2 O 2 -scavenging activity of only 17% at the highest concentration tested (1 mM). Cudraflavone B (1) showed the best activity against hypochlorous acid (IC50 1.8 ± 0.1 μM). Oh et al. tested 1 with DPPH and found its antioxidant activity to be 10-fold lower than that of oxyresveratrol.16 Some compounds induce the production of ROS in cells, which in turn may be responsible for beneficial properties.22,23 1587



Article

increased after a 30 min incubation and was attenuated after a 24 h incubation (a 1.67-fold higher level of ROS in comparison to the basal concentration of ROS after 30 min and a 1.26-fold lower level of ROS in comparison to the basal concentration of ROS after 24 h, respectively). The level of ROS decreased in the presence of 1, when the short- and longterm incubations were compared (a 3.12-fold higher level of ROS in comparison to the basal concentration of ROS after 30 min and a 2.00-fold lower level of ROS in comparison to the basal concentration of ROS after 24 h). However, the ROS concentration was still twice as high as the basal level after this long-term incubation. To determine whether the anti- or pro-oxidative properties of the test flavonoids are connected to their anti-inflammatory action, the activation of the NF-κB signaling pathway was investigated. One of the crucial steps in the activation of the canonical (classical) NF-κB pathway is the degradation of the NF-κB inhibitor IκB-α.26 Pretreatment of the cells with tested flavonoids led to reduced IκB-α degradation (Figure 4), where compounds 3 and 4 showed greater activity than 1 and 2. These results support previous observations made of an immunomodulating effect for compounds 1 and 4.15,19 An apparent discrepancy was observed between the pro-oxidant effect of 1 and its protective action against LPS-induced IκB-α degradation. However, it should be noted that LPS alone did not induce the production of ROS in a 30 min challenge test (Figure 1); hence the anti-inflammatory effect of the flavonoids tested must derive from some mechanism other than the antioxidant property. A higher level of IκB-α had a downstream effect on gene expression, as was determined by measuring the synthesis of COX-2 (Figure 5), which is regulated by the transcription factor NF-κB. The level of COX-2 correlates well with the level of IκB-α; that is, the greater the amount of IκB-α, the lower the amount of COX-2. From this viewpoint, only diplacone (4) showed a trend to reduce the expression of COX-2. Surprisingly, cudraflavone B (1), which had significantly attenuated the transcription of the COX-2 gene in our previous work,15 had no effect on the translation of COX-2 in this study. One reason for this could be that the concentration of 1 used in the present study was eight times lower than in the previous study. The present results have confirmed the ability of the test flavonoids to act as antioxidants in cell-free models in the decreasing order diplacone (4) > cudraflavone B (1) ≈ pomiferin (2) ≫ osajin (3). This antioxidant potential results from the number and position of the hydroxy groups on the Bring; the catechol moiety is especially crucial for this effect. The low antioxidant action in cell-free models correlates with the pro-oxidant properties of 1 and 3 in J774A.1 cells during 24 h of incubation. Compounds 1 and 3 also showed enhanced production of ROS in LPS-stimulated cells. On the other hand, no relationship was found between chemical structure and antiinflammatory effects. The most promising potential agent for the treatment of inflammatory diseases is diplacone (4), which has demonstrated beneficial effects in different settings including alloxan-induced diabetes mellitus in vivo.18 Cudraflavone B (1) might be useful as a potential anticancer agent because of its pro-oxidant action. However, detailed in vivo studies will be required to elucidate the efficacy and exact mechanisms of action of these flavonoids.

Figure 2. Effect of flavonoids on the LPS-induced production of ROS. J774A.1 cells were pretreated for 1 h with cudraflavone B (1), pomiferin (2), osajin (3), diplacone (4) (1.25 or 0.25 μM; concentrations are indicated below the graph), or only the vehicle (DMSO). Subsequently, LPS (1 μg/mL) was added and the level of ROS was measured after incubation for 24 h. (** indicates a significant difference (p < 0.01) in comparison with cells treated only with the vehicle and LPS, *** indicates a significant difference (p < 0.001) in comparison with cells treated only with the vehicle and LPS. The dashed line indicates a basal level of ROS production of LPS-treated cells.)

in the presence of LPS, by factors of 1.71 and 1.59, respectively. To determine whether this effect was related to the pro-oxidant properties of the chosen flavonoids that were detected in a short-term experiment (30 min), the level of ROS was also measured after a 24-h incubation (Figure 3). The present data

Figure 3. Effect of flavonoids on the 24 h production of ROS. J774A.1 cells were incubated with cudraflavone B (1), pomiferin (2), osajin (3), diplacone (4) (1.25 μM), or only the vehicle (DMSO). After 24 h, the production of ROS was measured. The results are expressed as the means ± SE for four independent experiments. The dashed line indicates a basal level of ROS production in J774.A1 cells.

indicated that 1 and 3 still failed to change the level of ROS at this time point (24 h). Taken together, cudraflavone B (1) and osajin (3) enhanced the LPS-induced production of ROS. These effects correlate well with the low antioxidant properties of 1 and 3. From a comparison of Figure 1 with Figure 3 it is evident that the level of ROS for compound 2 was similar after 30 min and 24 h incubations. On the other hand, 3 increased the generation of ROS during longer incubations. In the presence of diplacone (4), the production of ROS was 1588



Article

Figure 4. Effect of flavonoids on the LPS-induced degradation of IκB-α. J774A.1 cells were pretreated for 15 min with cudraflavone B (1), pomiferin (2), osajin (3), diplacone (4) (1.25 or 0.25 μM), or only the vehicle (DMSO). Subsequently, LPS (1 μg/mL) was added and the levels of IκB-α and β-actin were measured after 30 min. The basal level of expression (without LPS stimulation) of IκB-α is indicated, as well. The blots shown are representative results from four independent experiments. The graph below the blots indicates the IκB-α/β-actin ratio.

Figure 5. Effect of flavonoids on the LPS-induced expression of COX-2. J774A.1 cells were pretreated for 1 h with cudraflavone B (1), pomiferin (2), osajin (3), diplacone (4) (1.25 or 0.25 μM), or only the vehicle (DMSO). Subsequently, LPS (1 μg/mL) was added, and the levels of COX-2 and β-actin were measured after 24 h. The basal level of expression (without LPS stimulation) of COX-2 is indicated, as well. The blots shown are representative results from four independent experiments. The graph below the blots indicates the COX-2/β-actin ratio.

■

diplacone (4)17]. The purity of all compounds tested was checked via HPLC analysis and exceeded 95%. Superoxide Scavenging Assay. The superoxide radical (O2•−) was generated by the NADH/phenazine methosulfate (PMS) system, following the methodology described by Valantao et al.27 The final volume of 300 μL of reaction mixture in each sample well contained the following reagents at the indicated final concentrations: 19 mM

EXPERIMENTAL SECTION

Test Compounds. All four of the flavonoids were generously donated by Dr. Karel Šmejkal of the Faculty of Pharmacy, University of Veterinary and Pharmaceutical Sciences Brno, Brno, Czech Republic. They were isolated and characterized as previously described [i.e., cudraflavone B (1),15 pomiferin (2) and osajin (3),20 and 1589



Article

[the final concentration of DMSO in the medium was 0.1% (v/v)] and added 30 min before the end of the DCFH2-DA incubation at concentrations of 0.25 and 1.25 μM. At these levels, none of the compounds induced a toxic effect (data not shown). The medium was then aspirated, and the cells were washed with PBS. PBS with lidocaine and a scraper were used to harvest the cells. The level of oxidized 2′,7′dichlorfluorescein (DCF) was measured by flow cytometry at 488 nm for excitation and 525 nm for emission. The measurements were performed on a Beckman Coulter Epics XL flow cytometer. To detect the potential ability of the test flavonoids to inhibit the production of ROS in the presence of lipopolysaccharide obtained from Escherichia coli 0111:B4 (Sigma-Aldrich), the cells were pretreated with test compounds at concentrations of 0.25 and 1.25 μM for 1 h. Subsequently, 1 μg/mL LPS dissolved in water was added, and the cells were incubated for a further 24 h. DCFH2-DA was added 30 min before the end of the LPS incubation. Next, the cells were collected and the production of ROS was measured as described above. IκB-α Detection. The J774.A1 cells were prepared as described above and pretreated with the tested compounds at a concentration of 1.25 μM for 15 min. Then, 1 μg/mL LPS was added and the incubation was continued for a further 30 min. The cells were washed with PBS and lysed in lysis buffer [50 mM Tris-HCl, pH 7.4; 150 mM NaCl; 1% (v/v) Nonidet P-40; 25 mM NaF; 0.5% (w/v) sodium deoxycholate; 10% (w/v) SDS; 1 mM EGTA; 1 mM phenylmethylsulfonyl fluoride; 1 mM orthovanadate; and 10 mM sodium pyrophosphate, supplemented with Complete protease inhibitor mixture obtained from Roche, Mannheim, Germany] with sonication. The protein concentration was measured by the Lowry method.30 Cell lysates were denatured in the presence of β-mercaptoethanol at 100 °C for 5 min, and 40 μg of the denatured protein was loaded onto a 12% polyacrylamide gel. After electrophoresis, the protein was transferred to polyvinylidene difluoride (PVDF) membranes, which were subsequently blocked with 5% (w/v) skimmed milk (Sigma-Aldrich) dissolved in TBST buffer [150 mM NaCl, 10 mM Tris base, 0.1% (v/ v) Tween-20]. The membranes were incubated with either a primary anti-IκB-α antibody (Cell Signaling, Danvers, MA, USA) at 1:1000 dilution and 4 °C for 16 h or a primary anti-β-actin antibody (SigmaAldrich) at 1:5000 dilution and room temperature for 1 h. After washing, the secondary antibody [anti-mouse IgG; anti-rabbit IgG (Vector, Peterborough, UK)] diluted 1:5000 was applied on the membranes and incubated for 1 h at room temperature (∼23 °C). The secondary antibodies were detected using a chemiluminiscent ECL substrate (GE Healthcare, Little Chalfont, UK). The intensity of protein bands was calculated by AlphaEasy FC 4.0.0 software (Alpha Innotech, San Leandro, CA, USA) for densitometric analysis. COX-2 Detection. J774A.1 macrophages prepared as described above were pretreated with each of the test compounds at a concentration of 1.25 μM for 1 h. The inflammatory response was then triggered using 1 μg/mL LPS, and the cells were incubated for 24 h. The cells were lysed, and their protein concentrations were measured as described above. Forty micrograms of the denatured protein was loaded into a 12% polyacrylamide gel and blotted onto a PVDF membrane. The primary anti-COX-2 antibody (Cayman Chemicals, Ann Arbor, MI, USA) was diluted 1:500. β-Actin detection and membrane development was performed as described above. Statistical Analysis. All of the experiments were performed in at least three independent replications; the results are presented as mean values, with error bars representing the standard deviation (SE) of the average value. A one-way ANOVA test was used for statistical analysis, followed by Tukey’s post hoc test for multiple comparisons. A value of p < 0.05 was considered to be statistically significant. GraphPad Prism 5.02 (GraphPad Software Inc., La Jolla, CA, USA) was used to perform the analysis.

phosphate buffer, pH 7.4; test compound dissolved in dimethyl sulfoxide (DMSO) at concentrations ranging from 12.5 to 1000 μM; 166 μM NADH; 43.3 μM nitrotetrazolium blue (NBT); and 2.7 μM PMS (all compounds were purchased from Sigma-Aldrich, Steinheim, Germany). The assays were performed on a Biotek microplate reader. The absorbance was measured at 560 nm immediately after mixing all reagents for 2 min at room temperature. The absorbance was increased by the O2•−-reduction of NBT to a diformazan. Each compound was measured in five independent experiments, performed in triplicate. Hydrogen Peroxide Scavenging Assay. The H2O2 scavenging assay was performed according to the chemiluminescence method described by Gomes et al.28 The light emitted as lucigenin disintegrated to form methylacridine was monitored as an indication of the H2O2-induced oxidation. In a final volume of 250 μL, each reaction mixture contained 50 mM Tris-HCl buffer, pH 7.4; a test compound dissolved in DMSO at concentrations ranging from 125 to 1000 μM; 800 μM lucigenin (Sigma-Aldrich); and 1% (v/v) H2O2. The assays were performed on a Biotek microplate reader in the luminescent mode. Measurements were taken at 37 °C immediately after all of the reagents were mixed and added to the plate. Each compound was measured in five independent experiments, performed in triplicate. Hypochlorous Acid Scavenging Assay. The scavenging activity with HClO was measured using a modified version of the fluorescence methodology described by Gomes et al.29 The nonfluorescent agent dihydrorhodamine 123 (DHR) was oxidized to the fluorescent rhodamine by hypochlorous acid. The final volume of 300 μL of each reaction mixture in its sample well contained the following reagents at the specified final concentrations: 100 mM phosphate buffer, pH 7.4; a test compound dissolved in methanol at concentrations ranging from 0.625 to 100 μM; 5 μM DHR; and 5 μM HClO (all compounds were purchased from Sigma-Aldrich). The assays were measured on a Biotek microplate reader in the fluorescent mode. Measurements using excitation at 485 ± 20 nm and emission at 528 ± 20 nm were taken at 37 °C immediately after mixing all of the reagents and adding them into the plate. Each compound was measured in five independent experiments, performed in triplicate. Maintenance and Subcultivation of the Cell Line J774.A1. The murine macrophage cell line J774A.1 (Lonza, Verveirs, Belgium) was cultivated in Dulbecco’s modified Eagle medium (DMEM) containing 0.45% (w/v) glucose and 25 mM HEPES [4-(2hydroxyethyl)-1-piperazineethanesulfonic acid] (Life Technologies, Monza, Italy) with the addition of 10% (v/v) fetal bovine serum (FBS) (Euroclone, Milano, Italy), 1% (w/v) penicillin/streptomycin, and 1% (w/v) L-glutamine (Life Technologies) in a humidified atmosphere containing 5% CO2 at 37 °C. Cells were subcultivated when the confluence reached 80−90%. The culture medium was aspirated, and the cells were washed with phosphate-buffered saline (PBS) (Life Technologies). Adherent cells were detached by adding 1.5 mL of PBS containing 8 mg/mL lidocaine (Sigma-Aldrich) and 5 mM ethylenediaminetetraacetic acid (EDTA) (Sigma-Aldrich) for each 10 mm culture plate. Culture plates were then returned to the incubator for 2 min. A further 3 mL of PBS was then added to each plate, and the cells were scraped into sterile centrifuge tubes. After centrifugation at 1000g for 5 min, the supernatant was removed, and the cells were resuspended in fresh DMEM and transferred into new culture plates. In Vitro Measurement of Reactive Oxygen Species. J774A.1 cells were split into 30 mm dishes at a cell density of 250 000 cells/mL in a total volume of 2 mL. When the confluence had reached 80−90% after 36−48 h, the culture medium was removed and the cells were washed with PBS. Fresh serum-free DMEM was then added to the cells. The cells prepared in this manner were used for subsequent ROS measurements. To measure the ability of the test compounds to induce the generation of reactive oxygen species during a short-term (30 min) exposure, the cells were incubated for 1 h with 10 μM 2′,7′dichlorodihydrofluorescein-diacetate (DCFH2-DA) (Sigma-Aldrich) dissolved in methanol [the final concentration of methanol in the medium was 2% (v/v)]. The test compound was dissolved in DMSO

■

AUTHOR INFORMATION

Corresponding Author

*Tel: +420-541562839. Fax: +420-541240606. E-mail: [email protected]. 1590



Article

Notes

(25) Park, H. S.; Jung, H. Y.; Park, E. Y.; Kim, J.; Lee, W. J.; Bae, Y. S. J. Immunol. 2004, 173, 3589−3593. (26) Perkins, N. D.; Gilmore, T. D. Cell Death Differ. 2006, 13, 759− 772. (27) Valentao, P.; Fernandes, E.; Carvalho, F.; Andrade, P. B.; Seabra, R. M.; Bastos, M. L. J. Agric. Food Chem. 2002, 50, 4989−4993. (28) Gomes, A.; Costa, D.; Lima, J. L.; Fernandes, E. Bioorg. Med. Chem. 2006, 14, 4568−4577. (29) Gomes, A.; Fernandes, E.; Silva, A. M.; Santos, C. M.; Pinto, D. C.; Cavaleiro, J. A.; Lima, J. L. Bioorg. Med. Chem. 2007, 15, 6027− 6036. (30) Lowry, O. H.; Rosebrough, N. J.; Farr, A. L.; Randall, R. J. J. Biol. Chem. 1951, 193, 265−275.

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We acknowledge Dr. F. Thomas Campbell for critical reading of the manuscript. Financial support of this work by European Programme “Operational Programme Education for Competitiveness”, registration number CZ.1.07/2.3.00/30.0014 (to J.H.), and the Internal Grant Agency of the University of Veterinary and Pharmaceutical Sciences Brno (IGA VFU), grant number 83/2012/FaF (to O.N.), is gratefully acknowledged.

■

REFERENCES

(1) Han, R. M.; Zhang, J. P.; Skibsted, L. H. Molecules 2012, 17, 2140−2160. (2) Gulcin, I. Arch. Toxicol. 2012, 86, 345−391. (3) Galati, G.; O’Brien, P. J. Free Radical Biol. Med. 2004, 37, 287− 303. (4) Kweon, M. H.; Adhami, V. M.; Lee, J. S.; Mukhtar, H. J. Biol. Chem. 2006, 281, 33761−33772. (5) Pullikotil, P.; Chen, H.; Muniyappa, R.; Greenberg, C. C.; Yang, S.; Reiter, C. E.; Lee, J. W.; Chung, J. H.; Quon, M. J. J. Nutr. Biochem. 2012, 23, 1134−1145. (6) Gonzalez, R.; Ballester, I.; Lopez-Posadas, R.; Suarez, M. D.; Zarzuelo, A.; Martinez-Augustin, O.; Sanchez de, M. F. Crit. Rev. Food Sci. Nutr. 2011, 51, 331−362. (7) Loke, W. M.; Proudfoot, J. M.; Stewart, S.; McKinley, A. J.; Needs, P. W.; Kroon, P. A.; Hodgson, J. M.; Croft, K. D. Biochem. Pharmacol. 2008, 75, 1045−1053. (8) Bubici, C.; Papa, S.; Dean, K.; Franzoso, G. Oncogene 2006, 25, 6731−6748. (9) Morgan, M. J.; Liu, Z. G. Cell Res. 2011, 21, 103−115. (10) Pahl, H. L. Oncogene 1999, 18, 6853−6866. (11) Ghosh, S.; Hayden, M. S. Nat. Rev. Immunol. 2008, 8, 837−848. (12) Hybertson, B. M.; Gao, B.; Bose, S. K.; McCord, J. M. Mol. Aspects Med. 2011, 32, 234−246. (13) Kuhn, A. M.; Tzieply, N.; Schmidt, M. V.; von Knethen, A.; Namgaladze, D.; Yamamoto, M.; Brune, B. Free Radical Biol. Med. 2011, 50, 1382−1391. (14) Gloire, G.; Legrand-Poels, S.; Piette, J. Biochem. Pharmacol. 2006, 72, 1493−1505. (15) Hošek, J.; Bartoš, M.; Chudík, S.; Dall’acqua, S.; Innocenti, G.; Kartal, M.; Kokoška, L.; Kollár, P.; Kutil, Z.; Landa, P.; Marek, R.; Závalová, V.; Ž emlička, M.; Šmejkal, K. J. Nat. Prod. 2011, 74, 614− 619. (16) Oh, H.; Ko, E. K.; Jun, J. Y.; Oh, M. H.; Park, S. U.; Kang, K. H.; Lee, H. S.; Kim, Y. C. Planta Med. 2002, 68, 932−934. (17) Šmejkal, K.; Grycová, L.; Marek, R.; Lemiere, F.; Jankovská, D.; Forejtníková, H.; Vančo, J.; Suchý, V. J. Nat. Prod. 2007, 70, 1244− 1248. (18) Zima, A.; Hošek, J.; Treml, J.; Muselík, J.; Suchý, P.; Pražanová, G.; Lopes, A.; Ž emlička, M. Molecules 2010, 15, 6035−6049. (19) Hošek, J.; Závalová, V.; Šmejkal, K.; Bartoš, M. Folia Biol. (Praha) 2010, 56, 124−130. (20) Veselá, D.; Kubínová, R.; Muselík, J.; Ž emlička, M.; Suchý, V. Fitoterapia 2004, 75, 209−211. (21) Diopan, V.; Babula, P.; Shestivska, V.; Adam, V.; Zemlicka, M.; Dvorska, M.; Hubalek, J.; Trnkova, L.; Havel, L.; Kizek, R. J. Pharm. Biomed. Anal. 2008, 48, 127−133. (22) Lambert, J. D.; Elias, R. J. Arch. Biochem. Biophys. 2010, 501, 65−72. (23) Constantin, R. P.; Constantin, J.; Pagadigorria, C. L.; IshiiIwamoto, E. L.; Bracht, A.; de Castro, C. V.; Yamamoto, N. S. J. Biochem. Mol. Toxicol. 2011, 25, 117−126. (24) Toniolo, A.; Buccellati, C.; Pinna, C.; Gaion, R. M.; Sala, A.; Bolego, C. PLoS One 2013, 8, e56683. 1591


Prenylated and Geranylated Flavonoids Increase Production of

Recommend Documents