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Twice acting antioxidants: synthesis and antioxidant properties of selenium and sulfur-containing zingerone derivatives
Tetrahedron Letters 56 (2015) 2243–2246
Contents lists available at ScienceDirect
Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet
Twice acting antioxidants: synthesis and antioxidant properties of selenium and sulfur-containing zingerone derivatives Débora M. Martinez a, Angelita M. Barcellos a, Angela M. Casaril b, Lucielli Savegnago b,⇑, Gelson Perin a, Carl H. Schiesser c,d,⇑, Kimberley L. Callaghan c,d, Eder J. Lenardão a,⇑ a
CCQFA, Laboratório de Síntese Orgânica Limpa, Universidade Federal de Pelotas, PO Box 354, CEP: 96010-900 Pelotas, RS, Brazil Centro de Desenvolvimento Tecnológico, Unidade Biotecnologia, Universidade Federal de Pelotas, PO Box 354, CEP: 96010-900 Pelotas, RS, Brazil ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Australia d School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia b c
a r t i c l e
i n f o
Article history: Received 22 January 2015 Revised 5 March 2015 Accepted 6 March 2015 Available online 18 March 2015 Keywords: Organoselenium compounds Organosulfur compounds Dehydrozingerone Zingerone Antioxidants
a b s t r a c t Two new organochalcogen-containing zingerone derivatives, 4-(4-hydroxy-3-methoxyphenyl)4-(phenylseleno)-2-butanone (2b) and 4-(4-hydroxy-3-methoxyphenyl)-4-(phenylthio)-2-butanone (2c) were prepared and evaluated for their antioxidant properties. DPPH and lipid peroxidation studies show that 2b and 2c have significantly improved antioxidant activity over dehydrozingerone (1) despite having similar electron transfer capacity. We speculate that the improved activity of 2b and 2c is partly due to the ability of these compounds to act twice as phenolic antioxidants through a mechanism that eliminates phenylselenyl or phenylthiyl radicals. Ó 2015 Elsevier Ltd. All rights reserved.
Introduction Dehydrozingerone (DHZ, 1) and zingerone (2a) are phenolic compounds that are structurally related to curcumin (3) and are present as minor components in ginger, the rhizomes of Zingiber officinale Rosco (Fig. 1).1 DHZ along with vanillin and ferulic acid, are formed as degradation products of curcumin at physiological pH.2 Ginger has been widely used both as an ingredient and flavoring in foods, as well as a medicinal agent.3 Several pharmacological studies have been reported for ginger extracts3b or their constituents DHZ and zingerone.4 In particular, DHZ has been reported to have radioprotective,3a antimicrobial,4a,b prohealing,4c antioxidant,2,4a,c–j anti-Parkinson,4d antimutagenic,4k anti-cancer4l,m and antidiarrheal4n properties. The imbalance of oxidative metabolism has a crucial role in the progression of chronic diseases. Reactive Oxygen Species (ROS) are constantly formed in mammalian systems,5 either as accidental products during physiological processes,5a or due to environmental pollutants such as ozone,5b heavy metal poisoning5c and ionizing radiation.5d If ROS are not controlled by cellular antioxidant defences, they can generate a state of ⇑ Corresponding authors. E-mail addresses: [email protected] (L. Savegnago), [email protected]. au (C.H. Schiesser), [email protected] (E.J. Lenardão). http://dx.doi.org/10.1016/j.tetlet.2015.03.030 0040-4039/Ó 2015 Elsevier Ltd. All rights reserved.
Figure 1. Dehydrozingerone (1), zingerone (2a) and related compounds.
oxidative stress.6 The resulting ROS are responsible for the progressive and irreversible decline of various metabolic functions of the organism during aging, leading to conditions that include a decline in fertility,7a–c dementia7d and cancer.7e Besides being versatile intermediates in organic synthesis,8 organochalcogen compounds frequently exhibit biological activity, including antioxidant, antinociceptive, anticancer, antidepressant, antibacterial, and antifungal properties.9 Novel organochalcogen
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compounds were recently synthesized and proved to be strong antioxidants.9,10 In this context, the antioxidant properties of organoselenium compounds, such as mono- and diselenides, have been demonstrated through in vitro and in vivo model studies.9 The combination of two or more bioactive moieties in one molecule has been used as an effective strategy for designing new drugs and promising results with different classes of compounds have been described.11 Based on the known bioactivities of DHZ and chalcogen-containing compounds, together with our interest in the preparation and study of the biological activities of semi-synthetic organochalcogen molecules,12 we present herein the synthesis and the antioxidant evaluation of new derivatives of zingerone 2b–c (Fig. 1). The effect of chemical modifications on the antioxidant capacity of the molecules in question was examined using methods previously reported by us for this class of compound.12 Methods employed include: 2,2-diphenyl-1-picrylhydrazyl (DPPH)-scavenging, 2,2-azinobis-3-ethyl-benzothiazoline-6-sulfonic acid radical cation (ABTS+)-scavenging, linoleic acid peroxidation and anti-hemolysis activity assays. These assays provide important information about the hydrogen-transfer and electron-donating abilities of the compounds in question with regard to free radicals, and their protective capacity against lipid peroxidation in homogeneous and heterogeneous environments. Results and discussion Synthesis of dehydrozingerone analogues The overall strategy for the synthesis of the DHZ analogues (2b–c) is outlined in Schemes 1 and 2. Compound 1 was prepared by aldol condensation of vanillin with acetone (Scheme 1).4i The conjugate addition of an organochalcogen group to a,b-unsaturated carbonyl compounds is an efficient strategy for C–S and C–Se bond formation.13 Traditional methods for thia-Michael addition require Lewis acid activation of the acceptor olefin or deprotonation of the thiol.14 To prepare selenium-Michael adducts, benzeneselenol is frequently generated in situ from diphenyl diselenide in acidic media,15a or by using the (PhSe)2/NaBH4/PEG-400 system.15b Alternatively, the nucleophilic 1,4-addition of C6H5 SeZnCl in water has been successfully employed to prepare b-phenylseleno ketones.15c Accordingly, treatment of dehydrozingerone (1) with benzeneselenol that was generated in situ from diphenyl diselenide and sodium borohydride in ethanol and acetic acid15a,16 afforded 4-(4-hydroxy-3-methoxyphenyl)-4-(phenylseleno)-2-butanone (4-(phenylseleno)zingerone, 2b) in 21% yield (Scheme 2). Attempts to improve the yield of 2b from 1 using alternative methods for the generation of PhSeH failed.15b,c,17 This indicated that the addition of acid was crucial to minimize reduction of the carbonyl group in 1. Decomposition of 2b to zingerone (1) and diphenyl
Scheme 1.
Scheme 2.
diselenide during workup and/or competitive reduction of the carbonyl group contributed to the modest yield of 2b. Due to this instability, 2b was purified by flash chromatography or preparative TLC and used immediately in the antioxidant assays (vide infra). Similarly, 4-(phenylthio)zingerone (2c) was prepared by the Michael addition of benzenethiol to DHZ in 86% yield, using solid-supported KF in glycerol as the solvent (Scheme 2).14c,18 Radical scavenging activity A series of in vitro antioxidant screening methods were used to explore the antioxidant potential of compounds 1 (control) and 2b–c. Initial experiments were carried out in order to evaluate the ability of these compounds to scavenge 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH) and provides information about the ability of these compounds to donate hydrogen atoms to N-centered radicals. While details of this assay are provided elsewhere,12 it is important to note that assay is not affected by metal ion chelation or enzyme inhibition.19 Based on the calculated IC50 values, the DPPH radical-scavenging activity follows the order: 2b = 2c > 1. To our surprise, the data in Table 1 show that the DHZ derivatives 2b–c are approximately twice as effective at scavenging DPPH when compared with DHZ (1). This observation is consistent with the mechanism depicted in Scheme 3, and the observation that 2b is unstable, affording 1 and diphenyl diselenide upon workup (vide supra). Accordingly, we propose that DHZ derivatives 2b–c ‘act twice’, firstly through direct hydrogen atom transfer (HAT) to DPPH, and secondly through HAT from DHZ (1) which is produced through e-scission of the intermediate radical 4 followed by tautomerism (Scheme 3). We next examined the interaction of these compounds with the radical cation derived from 2,20 -azino-bis(3-ethylbenzothiazoline6-sulfonic acid) (ABTS+) which provides information on the ability of these compounds to become involved in electron-transfer chemistry. This would serve as a measure of the effectiveness of compounds to reduce radicals by electron transfer.12,20 As shown by the IC50 data in Table 2, all compounds (1, 2b, and 2c) show similar potency in this assay as expected due to the commonly substituted aromatic p-systems of these compounds. The ability of antioxidants to inhibit lipid peroxidation is important since this is implicated in cardiovascular disease.21 Consequently, the ability of 1 and 2b–c to inhibit direct lipid oxidation was evaluated in a linoleic acid emulsion. Linoleic acid oxidation generates lipid peroxides and hydroperoxides, that decompose to secondary oxidation products such as malondialdehydes (MDA). The thiobarbituric acid-reactive substances (TBARS) assay was used to evaluate the possible effects of 1 and its analogues in decreasing lipid peroxidation.12 Table 3 illustrates the effect of different concentrations of these compounds against linoleic acid peroxidation induced by sodium nitroprusside (SNP).22 Compounds 2b–c demonstrate a clear capacity to reduce lipid peroxidation by more than 50%, with 2b showing the best antioxidant capacity (IC50 = 66.3 ± 3.6 lM). Based on these results, it can be concluded that the addition of the Se-aryl group results in a
Table 1 Radical scavenging activity of DHZ (1) and derivatives (2b–c) toward DPPH Compound
Imax
IC50 (lM)
n
1 2b 2c
82.4 ± 3.6 96.6 ± 3.0 96.3 ± 3.3
57.0 ± 2.5 27.7 ± 9.6 33.3 ± 3.5
0.4 0.9 0.7
Data are expressed as mean ± standard error (SE) of % maximal inhibition (Imax) and concentration required to scavenge 50% of DPPH (IC50); n = stoichiometric factor (equivalents of radicals quenched by 1 equiv of substrate).
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Table 4 Time to half-lysis of RBC (mice) induced by AAPH (50 mM) with and without additive Sample
Time (min) 10 lM additive
AAPH AAPH + 1 AAPH + 2b AAPH + 2c AAPH + quercertin
Time (min) 50 lM additive 102.0 ± 1.7
110.3 ± 6.1 104.2 ± 6.3 111.4 ± 6.9 119.8 ± 3.0
Data are expressed as mean ± standard error (SE). compared to control (AAPH).
108.6 ± 3.8 >180⁄⁄⁄ 152.4 ± 12.8⁄⁄⁄ >180⁄⁄⁄ ⁄⁄
p <0.01 and
⁄⁄⁄
p <0.001 when
activity and to evaluate the influence of endogenous constituents on antioxidant activity. 2,20 -Azobis(2-amidinopropane)hydrochloride (AAPH) induced hemolysis is a convenient assay that mimics erythrocytes undergoing oxidative stress. AAPH decomposes at 37 °C in aqueous solutions generating radicals that can react with O2 to generate peroxyl radicals (ROO) which can then react with polyunsaturated lipids. RBC membranes are damaged as a result of lipid peroxidation, loss of glutathione and membrane integrity leading to release of hemoglobin (hemolysis) and intracellular potassium ions.25 Mice RBCs12 were stable in the absence of AAPH and little hemolysis took place after 3 h (data not shown). Addition of 50 mM AAPH induced rapid hemolysis, with a half-hemolysis time of 102 min (Table 4). Organochalcogen compounds 2b–c and the natural antioxidant quercetin, at concentrations of 50 lM, effectively prolonged the time to half-hemolysis. However, at 10 lM, none of these compounds were effective. Furthermore, after 3 h, the RBC AAPH induced hemolysis (89.67%) was effectively decreased by 2b (42.65%), 2c (52.56%), and quercetin (33.48%) (data not shown).
Scheme 3.
Conclusions
Table 2 Radical scavenging activity of DHZ (1) and derivatives (2b–c) toward ABTS+ Compound
Imax
IC50 (lM)
n
1 2b 2c
96.6 ± 1.9 99.5 ± 0.8 99.6 ± 0.5
8.0 ± 1.0 8.0 ± 1.0 6.5 ± 0.5
6.3 6.3 7.8
Data are expressed as mean ± standard error (SE) of % maximal inhibition (Imax) and concentration required to scavenge 50% of DPPH (IC50); n = stoichiometric factor (equivalents of radicals quenched by 1 equiv of substrate).
significant increase in the ability of this structural class of compounds to inhibit lipid peroxidation. This is consistent with the observation that organoselenides in general are reactive toward peroxides and hydroperoxides.23 It is well established that the antioxidant activity of compounds in homogenous solutions may not be representative of their activity in heterogeneous media such as those found within cells and other in vivo environments.24 Consequently, we chose to explore the antioxidant activity of 1 and 2b–c in red blood cells (RBC) using the hemolysis model in order to further understand their biological
Two new organochalcogen-containing zingerone derivatives, 4-(4-hydroxy-3-methoxyphenyl)-4-(phenylseleno)-2-butanone (2b) and 4-(4-hydroxy-3-methoxyphenyl)-4-(phenylthio)-2-butanone (2c) were prepared and evaluated for their antioxidant properties. DPPH and lipid peroxidation studies showed that 2b and 2c have significantly improved antioxidant activity over dehydrozingerone (1), while an ABTS assay showed that all compounds have similar electron transfer capacity. We speculate that the improved activity of 2b and 2c is partly due to the ability of these compounds to act twice as phenolic antioxidants through a mechanism that eliminates phenylselenyl or phenylthiyl radicals. Acknowledgments This research was undertaken as part of the scientific activities of the international multidisciplinary SeS Redox and Catalysis network. We are grateful to CAPES, CNPq, FINEP, FAPERGS and the Australian Research Council (through the Centres of Excellence Scheme) for financial support.
Table 3 Antioxidant activity of DHZ (1) and derivatives (2b–c) against lipid peroxidation Concentration (lM)
Compound
1 2b 2c
10
50
100
500
85.1 ± 6.5 83.5 ± 5.8⁄ 98.4 ± 1.5
88.8 ± 8.8 52.7 ± 3.4⁄⁄⁄ 94.1 ± 3.6
88.5 ± 4.0 42.4 ± 6.5⁄⁄⁄ 80.6 ± 8.1⁄
86.4 ± 4.4 28.4 ± 3.0⁄⁄⁄ 57.6 ± 5.1⁄⁄
Imax
IC50 (lM)
12.1 ± 4.7 71.6 ± 5.3 42.4 ± 8.9
— 66.3 ± 3.6 —
Data are expressed as mean ± standard error (SE) of % lipid peroxidation. IC50 = concentration (lM) required to decrease 50% lipid peroxidation. Imax = % maximal inhibition. p <0.05. ⁄⁄p <0.01. ⁄⁄⁄p <0.001 when compared to control sample (SNP solution) by Student–Newman–Keuls test for post-hoc comparison.
⁄
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References and notes 1. (a) de Bernardi, M.; Vidari, G.; Vita-Finzi, P. Phytochemistry 1976, 15, 1785; (b) Connell, D. W.; Sutherland, M. D. Aust. J. Chem. 1969, 22, 1033. 2. Marchianni, A.; Mammi, S.; Siligardi, G.; Hussain, R.; Tessari, L.; Bubacco, L.; Delogu, G.; Fabbri, D.; Dettori, M. A.; Sanna, D.; Dedola, S.; Serra, P. A.; Ruzza, P. Amino Acids 2013, 45, 327. 3. (a) Baliga, M. S.; Haniadka, R.; Pereira, M. M.; Thilakchand, K. R.; Rao, S.; Arora, R. Food Funct. 2012, 3, 714; (b) Corrigan, D. In Adverse Effects of Herbal Drugs; de Smet, P. A. G. M., Keller, K., Hansel, R., Chandler, R. F., Eds.; Springer: Berlin, Heidelberg, 1997; vol. 3, pp 215–216. 4. (a) Kubra, I. R.; Bettadaiah, B. K.; Murthy, P. S.; Rao, L. J. M. J. Food Sci. Technol. 2014, 51, 245; (b) Kubra, I. R.; Murthy, P. S.; Rao, L. J. M. J. Food Sci. 2013, 78, M64; (c) Rao, M. C.; Sudheendra, A. T.; Nayak, P. G.; Paul, P.; Kutty, G. N.; Shenoy, R. R. Mol. Cell. Biochem. 2011, 355, 249; (d) Kabuto, H.; Nishizawa, M.; Tada, M.; Higashio, C.; Shishibori, T.; Kohno, M. Neurochem. Res. 2005, 30, 325; (e) Priyadarsini, K. I.; Devasagayam, T. P. A.; Rao, M. N. A.; Guha, S. N. Radiat. Phys. Chem. 1999, 54, 551; (f) Nugroho, A. E.; Yuniarti, N.; Estyastono, E. P.; Supardjan, ; Hakim, L. Majalah Farm. Ind. 2006, 17, 116; (g) Motohashi, N.; Takahashi, A.; Yamagami, C.; Saito, Y. Chem. Pharm. Bull. 2005, 53, 1003; (h) Priyadarsinia, K. I.; Guha, S. N.; Rao, M. N. A. Free Radical Biol. Med. 1998, 24, 933; (i) Kuo, P.-C.; Damu, A. G.; Cherng, C.-Y.; Jeng, J.-F.; Teng, C.-M.; Lee, E.-J.; Wu, T.-S. Arch. Pharm. Res. 2005, 28, 518; (j) Musialik, M.; Litwinienko, G. J. Therm. Anal. Calorim. 2007, 88, 781; (k) Motohashi, N.; Ashihara, Y.; Yamagami, C.; Saito, Y. Mutat. Res. 1997, 377, 17; (l) Tatsuzaki, J.; Bastow, K. F.; NakagawaGoto, K.; Nakamura, S.; Itokawa, H.; Lee, K.-H. J. Nat. Prod. 2006, 69, 1445; (m) Yogosawa, S.; Yamada, Y.; Yasuda, S.; Sun, Q.; Takizawa, K.; Sakai, T. J. Nat. Prod. 2012, 75, 2088; (n) Iwami, M.; Shiina, T.; Hirayama, H.; Shima, T.; Takewaki, T.; Shimizu, Y. J. Nat. Med. 2011, 65, 89. 5. (a) Schöneich, C. Exp. Gerontol. 1999, 34, 19; (b) Ueda, Y.; Uehara, N.; Sasaki, H.; Kobayashi, K.; Yamakawa, T. Plant Physiol. Biochem. 2013, 70, 396; (c) Rico, D.; Martín-González, A.; Díaz, S.; Lucas, P.; Gutiérrez, J.-C. Comp. Biochem. Physiol. 2009, 149, 90; (d) Yamamori, T.; Yasui, H.; Yamazumi, M.; Wada, Y.; Nakamura, Y.; Nakamura, H.; Inanami, O. Free Radical Biol. Med. 2012, 53, 260. 6. Sies, H. Angew. Chem., Int. Ed. Engl. 1986, 25, 1058. 7. (a) Agarwal, A.; Saleh, R. A.; Bedaiwy, M. A. Fertil. Steril. 2003, 79, 829; (b) AlGuborya, K. H.; Fowlerb, P. A.; Garrelc, C. Int. J. Biochem. Cell Biol. 2010, 42, 1634; (c) Taylor, C. T. Environ. Toxicol. Pharmacol. 2001, 10, 189; (d) Bennett, S.; Grant, M. M.; Aldred, S. J. Alzheimers Dis. 2009, 17, 245; (e) Reuter, S.; Gupta, S. C.; Chaturvedi, M. M.; Aggarwal, B. B. Free Radical Biol. Med. 2010, 49, 1603. and references therein. 8. (a)PATAI’s Chemistry of Functional Groups: Organic Selenium and Tellurium Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: Chichester, 2013; (b) Wirth, T. Organoselenium Chemistry: Synthesis and Reactions; Wiley-VCH: Weinheim, 2011; (c) Liotta, D. Organoselenium Chemistry; Wiley: New York, 1987; (d) Back, T. G. Organoselenium Chemistry: A Practical Approach; Oxford University Press: Oxford, 1999; (e) Perin, G.; Lenardão, E. J.; Jacob, R. G.; Panatieri, R. B. Chem. Rev. 2009, 109, 1277; (f) Freudendahl, D. M.; Santoro, S.; Shahzad, S. A.; Santi, C.; Wirth, T. Angew. Chem., Int. Ed 2009, 48, 8409; (g) Santi, C.; Santoro, S.; Battistelli, B. Curr. Org. Chem. 2010, 14, 2442. 9. (a) Nogueira, C. W.; Zeni, G.; Rocha, J. B. T. Chem. Rev. 2004, 104, 6255; (b) Prigol, M.; Nogueira, C. W.; Zeni, G.; Bronze, M. R.; Constantino, L. Chem.-Biol. Interact. 2012, 200, 65; (c) Tapiero, H.; Townsend, D. M.; Tew, K. D. Biomed. Pharmacother. 2003, 57, 134; (d) Arteel, G. E.; Sies, H. Environ. Toxicol. Pharmacol. 2001, 10, 153; (e) Engman, L.; Laws, M. J.; Malmström, J.; Schiesser, C. H.; Zugaro, L. M. J. Org. Chem. 1999, 64, 6764. 10. For examples: (a) Sartori, G.; Neto, J. S. S.; Pesarico, A. P.; Back, D. F.; Nogueira, C. W.; Zeni, G. Org. Biomol. Chem. 2013, 11, 1199; (b) Storkey, C.; Pattison, D. I.; White, J. M.; Schiesser, C. H.; Davies, M. J. Chem. Res. Toxicol. 2012, 25, 2589; (c) Savegnago, L.; Vieira, A. I.; Seus, N.; Goldani, B. S.; Castro, M. R.; Lenardão, E. J.; Alves, D. Tetrahedron Lett. 2013, 54, 40. 11. (a) Choi, S. K. Synthetic Multivalent Molecules; Wiley-Interscience: New York, 2004; (b) Bastow, K. F.; Wang, H. K.; Cheng, Y. C.; Lee, K. H. Bioorg. Med. Chem. 1997, 5, 1481; (c) Chang, J. Y.; Guo, X.; Chen, H. X.; Jiang, Z.; Fu, Q.; Wang, H. K.; Bastow, K. F.; Zhu, X. K.; Guan, J.; Lee, K. H.; Cheng, T. C. Biochem. Pharm. 2000, 59, 497; (d) Shi, Q.; Wang, H. K.; Bastow, K. F.; Tachibana, Y.; Chen, K.; Lee, F. Y.; Lee, K. H. Bioorg. Med. Chem. 2001, 9, 2999; (e) Ohtsu, H.; Nakanishi, Y.; Bastow, K. F.; Lee, F. Y.; Lee, K. H. Bioorg. Med. Chem. 2003, 11, 1851; (f) Nakagawa-Goto, K.; Nakamura, S.; Bastow, K. F.; Nyarko, A.; Peng, C. Y.; Lee, F. Y.; Lee, F. C.; Lee, K. H. Bioorg. Med. Chem. Lett. 2007, 17, 2894; (g) Tatsuzaki, J.; Taniguchi, M.; Bastow, K. F.; Nakagawa-Goto, K.; Morris-Natschke, S. L.; Itokawa, H.; Baba, K.; Lee, K. H. Bioorg. Med. Chem. 2007, 15, 6193; (h) Nakagawa-Goto, K.; Yamada, K.; Nakamura, S.; Chen, T.-H.; Chiang, P.-C.; Bastow, K. F.; Wang, S. C.; Spohn, B.; Hung, M. C.; Lee, F. Y.; Lee, F. C.; Lee, K. H. Bioorg. Med. Chem. Lett. 2007, 17, 5204; (i) Grange, R. L.; Ziogas, J.; North, A. J.; Angus, J. A.; Schiesser, C. H. Bioorg. Med. Chem. Lett. 2008, 18, 1241; (j) Aumann, K. M.; Scammells, P. J.; White, J.
12.
13.
14.
15.
16.
17. 18.
19. 20. 21. 22. 23. 24. 25.
M.; Schiesser, C. H. Org. Biomol. Chem. 2007, 5, 1276; (k) Ashton, T. D.; Aumann, K. M.; Baker, S. P.; Schiesser, C. H.; Scammells, P. J. Bioorg. Med. Chem. Lett. 2007, 17, 6779; (l) Staples, M. K.; Grange, R. L.; Angus, J. A.; Ziogas, J.; Tan, N. P. H.; Tayloe, M. K.; Schiesser, C. H. Org. Biomol. Chem. 2011, 9, 473. (a) Lenardão, E. J.; Jacob, R. G.; Mesquita, K. D.; Lara, R. G.; Webber, R.; Martinez, D. M.; Savegnago, L.; Mendes, S. R.; Alves, D.; Perin, G. Green Chem. Lett. Rev. 2013, 6, 269; (b) Victoria, F. N.; Radatz, C. S.; Sachini, M.; Jacob, R. G.; Alves, D.; Savegnago, L.; Perin, G.; Motta, A. S.; Silva, W. P.; Lenardão, E. J. Food Control 2012, 23, 95; (c) Victoria, F. N.; Anversa, R. G.; Penteado, F.; Castro, M.; Lenardão, E. J.; Savegnago, L. Eur. J. Pharm. 2014, 742, 131. Sala, G. S.; Lattanzi, A. C-Other Atom Bond Formation (S, Se, B) in Stereoselective Organocatalysis: Bond Formation Methodologies and Activation Modes; WileyBlackwell: Southampton, 2013. 493–523. (a) Ba˘doiu, A.; Bernardinelli, G.; Besnard, C.; Kündig, E. P. Org. Biomol. Chem. 2010, 8, 193; (b) Perin, G.; Mesquita, K.; Calheiro, T. P.; Silva, M. S.; Lenardão, E. J.; Alves, D.; Jacob, R. G. Synth. Commun. 2014, 44, 49; (c) Lenardão, E. J.; Trecha, D. O.; Ferreira, P. C.; Jacob, R. G.; Perin, G. J. Braz. Chem. Soc. 2009, 20, 93. (a) Miyashita, M.; Yoshikoshi, A. Synthesis 1980, 664; (b) Perin, G.; Borges, E. L.; Rosa, P. C.; Carvalho, P. N.; Lenardão, E. J. Tetrahedron Lett. 2013, 54, 1718; (c) Battistelli, B.; Lorenzo, T.; Tiecco, M.; Santi, C. Eur. J. Org. Chem. 2011, 10, 1848. Synthetic procedure: 4-(4-Hydroxy-3-methoxyphenyl)-4-(phenylseleno)-2butanone (2b): To a solution of diphenyl diselenide (0.312 g, 1.0 mmol) in ethanol (2.5 mL) under a N2 atmosphere, NaBH4 (0.049 g, 1.3 mmol) was added at room temperature and the mixture stirred for 30 min. The colorless (or faint yellow) solution of benzeneselenolate obtained was cooled to 0 °C in an ice bath and acetic acid (2.3 mmol) was added. A solution of DHZ 1 (0.192 g, 1.0 mmol) in ethanol (0.5 mL) was then added and the resulting mixture stirred at 0 °C for 4 h. After consumption of the starting materials (TLC), the mixture was diluted with ethyl acetate (15 mL) and washed with water (15 mL) and brine (3 15 mL). The organic phase was dried (MgSO4) and then concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel using ethyl acetate/hexane (30% v/v) as the eluent, yielding the product as a pale yellow solid. Yield: 0.074 g, 21%, mp 82– 85 °C, 1H NMR (400 MHz, CDCl3): d = 7.48–7.19 (m, 5H), 6.93–6.56 (m, 3H), 5.77 (br s, 1H), 4.73 (dd, J = 6.3 and 8.7 Hz, 1H), 3.75 (s, 3H), 3.19 (dd, J = 8.7 and 16.9 Hz, 1H), 3.02 (dd, J = 6.3 and 16.9 Hz, 1H), 2.04 (s, 3H). 13C NMR (100 MHz, CDCl3) d 205.8, 146.2, 144.8, 134.0, 132.9, 132.7, 128.8, 127.5, 120.2, 114.2, 110.4, 55.8, 49.7, 47.9, 30.7. IR (KBr pellet), m (cm1): 1276.9, 1514.1, 1689.6, 2968.4, 3361.9. MS (relative intensity) m/z: 194 (M+SePh, 5.5), 193 (43.9), 192 (34.5), 177 (35.8), 158 (26.5), 151 (15.9), 150 (21.4), 145 (63.1), 135 (18.4), 117 (28.0), 111 (12.3), 109 (11.3), 97 (23.2), 95 (19.3), 83 (25.3), 81 (26.3), 78 (70.6), 69 (38.7), 67 (17.9), 57 (40.5), 55 (37.7), 43 (100). HRMS (ES) for C17H18O3Se+Na ([M+Na]+): calcd: 373.0313; found: 373.0309. Günther, W. H. H. J. Org. Chem. 1966, 31, 1202. Synthetic procedure: 4-(4-Hydroxy-3-methoxyphenyl)-4-(phenylthio)butan-2one (2c). To a round-bottomed flask containing mixture of benzenephenol (0.065 g, 0.6 mmol) and KF/Al2O3 (0.07 g) in glycerol (1.0 mL) was added DHZ (1a, 0.058 g, 0.3 mmol). The reaction mixture was stirred at 90 °C for 4 h under a N2 atmosphere. After completion of the reaction (TLC), the mixture was cooled to room temperature, diluted with ethyl acetate (15 mL) and washed with aq NH4Cl (3 15 mL). The solvent was evaporated under reduced pressure and the residue was purified by column chromatography over silica gel eluting with hexane/ethyl acetate (20% v/v) yielding the product as a white solid. Yield: 0.078 g, 86%. White solid, mp 78–80 °C, 1H NMR (400 MHz, CDCl3): d = 7.34–7.24 (m, 5H), 6.64–6.77 (m, 3H), 5.71 (br s, 1H), 4.68 (dd, J = 6.6 and 8.1 Hz, 1H), 3.83 (s, 3H), 3.08 (dd, J = 16.8 and 8.1 Hz, 1H), 3.00 (dd, J = 16.8 and 6.6 Hz, 1H), 2.09 ppm (s, 3H). 13C NMR (100 MHz, CDCl3) d (ppm) 205.9, 146.4, 144.9, 134.1, 133.0, 132.8, 128.9, 127.6, 120.3, 114.3, 110.5, 55.9, 49.7, 48.0, 30.8. IR (KBr pellet), m (cm1): 1282.7, 1515.1, 1689.7, 2960.8, 3362.9. MS (relative intensity) m/z: 302 (M+, 0.2), 194 (5.1), 193 (42.0), 177 (2.0), 151 (10.6), 145 (3.0), 135 (5.5), 119 (1.4), 110 (5.5), 107 (2.4), 91 (2.1), 77 (4.3), 65 (3.1), 43 (100.0). HRMS (ES) for C17H18O3S+Na ([M+Na]+): calcd: 325.0869; found: 325.0874. Amarowicz, R.; Pegg, R. B.; Rahimi-Moghaddam, P.; Barl, B.; Weil, J. A. Food Chem. 2004, 84, 551. Re, R.; Pellegrini, N.; Proteggente, A.; Pannala, M.; Yang, M.; Rice-Evans, C. Free Radical Biol. Med. 1999, 26, 1231. Valko, M.; Leibfritz, D.; Moncol, J.; Cronin, T. D. M.; Mazur, M.; Telser, J. Int. J. Biochem. Cell Biol. 2007, 39, 44. Choi, C. W.; Kim, S. C.; Hwang, S. S.; Choi, B. K.; Ahn, H. J.; Lee, M. Y.; Park, S. H.; Kim, S. K. Plant Sci. 2002, 163, 1161. For a review, see: Alberto, E. E.; do Nascimento, V.; Braga, A. L. J. Braz. Chem. Soc. 2010, 21, 2032. Zhou, B.; Miao, Q.; Yang, L.; Liu, Z. L. Chem.-Eur. J. 2005, 11, 680. Banerjee, A.; Kunwar, A.; Mishra, B.; Priyadarsini, K. I. Chem.-Biol. Interact. 2008, 174, 134.
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Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet
Twice acting antioxidants: synthesis and antioxidant properties of selenium and sulfur-containing zingerone derivatives Débora M. Martinez a, Angelita M. Barcellos a, Angela M. Casaril b, Lucielli Savegnago b,⇑, Gelson Perin a, Carl H. Schiesser c,d,⇑, Kimberley L. Callaghan c,d, Eder J. Lenardão a,⇑ a
CCQFA, Laboratório de Síntese Orgânica Limpa, Universidade Federal de Pelotas, PO Box 354, CEP: 96010-900 Pelotas, RS, Brazil Centro de Desenvolvimento Tecnológico, Unidade Biotecnologia, Universidade Federal de Pelotas, PO Box 354, CEP: 96010-900 Pelotas, RS, Brazil ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Australia d School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia b c
a r t i c l e
i n f o
Article history: Received 22 January 2015 Revised 5 March 2015 Accepted 6 March 2015 Available online 18 March 2015 Keywords: Organoselenium compounds Organosulfur compounds Dehydrozingerone Zingerone Antioxidants
a b s t r a c t Two new organochalcogen-containing zingerone derivatives, 4-(4-hydroxy-3-methoxyphenyl)4-(phenylseleno)-2-butanone (2b) and 4-(4-hydroxy-3-methoxyphenyl)-4-(phenylthio)-2-butanone (2c) were prepared and evaluated for their antioxidant properties. DPPH and lipid peroxidation studies show that 2b and 2c have significantly improved antioxidant activity over dehydrozingerone (1) despite having similar electron transfer capacity. We speculate that the improved activity of 2b and 2c is partly due to the ability of these compounds to act twice as phenolic antioxidants through a mechanism that eliminates phenylselenyl or phenylthiyl radicals. Ó 2015 Elsevier Ltd. All rights reserved.
Introduction Dehydrozingerone (DHZ, 1) and zingerone (2a) are phenolic compounds that are structurally related to curcumin (3) and are present as minor components in ginger, the rhizomes of Zingiber officinale Rosco (Fig. 1).1 DHZ along with vanillin and ferulic acid, are formed as degradation products of curcumin at physiological pH.2 Ginger has been widely used both as an ingredient and flavoring in foods, as well as a medicinal agent.3 Several pharmacological studies have been reported for ginger extracts3b or their constituents DHZ and zingerone.4 In particular, DHZ has been reported to have radioprotective,3a antimicrobial,4a,b prohealing,4c antioxidant,2,4a,c–j anti-Parkinson,4d antimutagenic,4k anti-cancer4l,m and antidiarrheal4n properties. The imbalance of oxidative metabolism has a crucial role in the progression of chronic diseases. Reactive Oxygen Species (ROS) are constantly formed in mammalian systems,5 either as accidental products during physiological processes,5a or due to environmental pollutants such as ozone,5b heavy metal poisoning5c and ionizing radiation.5d If ROS are not controlled by cellular antioxidant defences, they can generate a state of ⇑ Corresponding authors. E-mail addresses: [email protected] (L. Savegnago), [email protected]. au (C.H. Schiesser), [email protected] (E.J. Lenardão). http://dx.doi.org/10.1016/j.tetlet.2015.03.030 0040-4039/Ó 2015 Elsevier Ltd. All rights reserved.
Figure 1. Dehydrozingerone (1), zingerone (2a) and related compounds.
oxidative stress.6 The resulting ROS are responsible for the progressive and irreversible decline of various metabolic functions of the organism during aging, leading to conditions that include a decline in fertility,7a–c dementia7d and cancer.7e Besides being versatile intermediates in organic synthesis,8 organochalcogen compounds frequently exhibit biological activity, including antioxidant, antinociceptive, anticancer, antidepressant, antibacterial, and antifungal properties.9 Novel organochalcogen
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compounds were recently synthesized and proved to be strong antioxidants.9,10 In this context, the antioxidant properties of organoselenium compounds, such as mono- and diselenides, have been demonstrated through in vitro and in vivo model studies.9 The combination of two or more bioactive moieties in one molecule has been used as an effective strategy for designing new drugs and promising results with different classes of compounds have been described.11 Based on the known bioactivities of DHZ and chalcogen-containing compounds, together with our interest in the preparation and study of the biological activities of semi-synthetic organochalcogen molecules,12 we present herein the synthesis and the antioxidant evaluation of new derivatives of zingerone 2b–c (Fig. 1). The effect of chemical modifications on the antioxidant capacity of the molecules in question was examined using methods previously reported by us for this class of compound.12 Methods employed include: 2,2-diphenyl-1-picrylhydrazyl (DPPH)-scavenging, 2,2-azinobis-3-ethyl-benzothiazoline-6-sulfonic acid radical cation (ABTS+)-scavenging, linoleic acid peroxidation and anti-hemolysis activity assays. These assays provide important information about the hydrogen-transfer and electron-donating abilities of the compounds in question with regard to free radicals, and their protective capacity against lipid peroxidation in homogeneous and heterogeneous environments. Results and discussion Synthesis of dehydrozingerone analogues The overall strategy for the synthesis of the DHZ analogues (2b–c) is outlined in Schemes 1 and 2. Compound 1 was prepared by aldol condensation of vanillin with acetone (Scheme 1).4i The conjugate addition of an organochalcogen group to a,b-unsaturated carbonyl compounds is an efficient strategy for C–S and C–Se bond formation.13 Traditional methods for thia-Michael addition require Lewis acid activation of the acceptor olefin or deprotonation of the thiol.14 To prepare selenium-Michael adducts, benzeneselenol is frequently generated in situ from diphenyl diselenide in acidic media,15a or by using the (PhSe)2/NaBH4/PEG-400 system.15b Alternatively, the nucleophilic 1,4-addition of C6H5 SeZnCl in water has been successfully employed to prepare b-phenylseleno ketones.15c Accordingly, treatment of dehydrozingerone (1) with benzeneselenol that was generated in situ from diphenyl diselenide and sodium borohydride in ethanol and acetic acid15a,16 afforded 4-(4-hydroxy-3-methoxyphenyl)-4-(phenylseleno)-2-butanone (4-(phenylseleno)zingerone, 2b) in 21% yield (Scheme 2). Attempts to improve the yield of 2b from 1 using alternative methods for the generation of PhSeH failed.15b,c,17 This indicated that the addition of acid was crucial to minimize reduction of the carbonyl group in 1. Decomposition of 2b to zingerone (1) and diphenyl
Scheme 1.
Scheme 2.
diselenide during workup and/or competitive reduction of the carbonyl group contributed to the modest yield of 2b. Due to this instability, 2b was purified by flash chromatography or preparative TLC and used immediately in the antioxidant assays (vide infra). Similarly, 4-(phenylthio)zingerone (2c) was prepared by the Michael addition of benzenethiol to DHZ in 86% yield, using solid-supported KF in glycerol as the solvent (Scheme 2).14c,18 Radical scavenging activity A series of in vitro antioxidant screening methods were used to explore the antioxidant potential of compounds 1 (control) and 2b–c. Initial experiments were carried out in order to evaluate the ability of these compounds to scavenge 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH) and provides information about the ability of these compounds to donate hydrogen atoms to N-centered radicals. While details of this assay are provided elsewhere,12 it is important to note that assay is not affected by metal ion chelation or enzyme inhibition.19 Based on the calculated IC50 values, the DPPH radical-scavenging activity follows the order: 2b = 2c > 1. To our surprise, the data in Table 1 show that the DHZ derivatives 2b–c are approximately twice as effective at scavenging DPPH when compared with DHZ (1). This observation is consistent with the mechanism depicted in Scheme 3, and the observation that 2b is unstable, affording 1 and diphenyl diselenide upon workup (vide supra). Accordingly, we propose that DHZ derivatives 2b–c ‘act twice’, firstly through direct hydrogen atom transfer (HAT) to DPPH, and secondly through HAT from DHZ (1) which is produced through e-scission of the intermediate radical 4 followed by tautomerism (Scheme 3). We next examined the interaction of these compounds with the radical cation derived from 2,20 -azino-bis(3-ethylbenzothiazoline6-sulfonic acid) (ABTS+) which provides information on the ability of these compounds to become involved in electron-transfer chemistry. This would serve as a measure of the effectiveness of compounds to reduce radicals by electron transfer.12,20 As shown by the IC50 data in Table 2, all compounds (1, 2b, and 2c) show similar potency in this assay as expected due to the commonly substituted aromatic p-systems of these compounds. The ability of antioxidants to inhibit lipid peroxidation is important since this is implicated in cardiovascular disease.21 Consequently, the ability of 1 and 2b–c to inhibit direct lipid oxidation was evaluated in a linoleic acid emulsion. Linoleic acid oxidation generates lipid peroxides and hydroperoxides, that decompose to secondary oxidation products such as malondialdehydes (MDA). The thiobarbituric acid-reactive substances (TBARS) assay was used to evaluate the possible effects of 1 and its analogues in decreasing lipid peroxidation.12 Table 3 illustrates the effect of different concentrations of these compounds against linoleic acid peroxidation induced by sodium nitroprusside (SNP).22 Compounds 2b–c demonstrate a clear capacity to reduce lipid peroxidation by more than 50%, with 2b showing the best antioxidant capacity (IC50 = 66.3 ± 3.6 lM). Based on these results, it can be concluded that the addition of the Se-aryl group results in a
Table 1 Radical scavenging activity of DHZ (1) and derivatives (2b–c) toward DPPH Compound
Imax
IC50 (lM)
n
1 2b 2c
82.4 ± 3.6 96.6 ± 3.0 96.3 ± 3.3
57.0 ± 2.5 27.7 ± 9.6 33.3 ± 3.5
0.4 0.9 0.7
Data are expressed as mean ± standard error (SE) of % maximal inhibition (Imax) and concentration required to scavenge 50% of DPPH (IC50); n = stoichiometric factor (equivalents of radicals quenched by 1 equiv of substrate).
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Table 4 Time to half-lysis of RBC (mice) induced by AAPH (50 mM) with and without additive Sample
Time (min) 10 lM additive
AAPH AAPH + 1 AAPH + 2b AAPH + 2c AAPH + quercertin
Time (min) 50 lM additive 102.0 ± 1.7
110.3 ± 6.1 104.2 ± 6.3 111.4 ± 6.9 119.8 ± 3.0
Data are expressed as mean ± standard error (SE). compared to control (AAPH).
108.6 ± 3.8 >180⁄⁄⁄ 152.4 ± 12.8⁄⁄⁄ >180⁄⁄⁄ ⁄⁄
p <0.01 and
⁄⁄⁄
p <0.001 when
activity and to evaluate the influence of endogenous constituents on antioxidant activity. 2,20 -Azobis(2-amidinopropane)hydrochloride (AAPH) induced hemolysis is a convenient assay that mimics erythrocytes undergoing oxidative stress. AAPH decomposes at 37 °C in aqueous solutions generating radicals that can react with O2 to generate peroxyl radicals (ROO) which can then react with polyunsaturated lipids. RBC membranes are damaged as a result of lipid peroxidation, loss of glutathione and membrane integrity leading to release of hemoglobin (hemolysis) and intracellular potassium ions.25 Mice RBCs12 were stable in the absence of AAPH and little hemolysis took place after 3 h (data not shown). Addition of 50 mM AAPH induced rapid hemolysis, with a half-hemolysis time of 102 min (Table 4). Organochalcogen compounds 2b–c and the natural antioxidant quercetin, at concentrations of 50 lM, effectively prolonged the time to half-hemolysis. However, at 10 lM, none of these compounds were effective. Furthermore, after 3 h, the RBC AAPH induced hemolysis (89.67%) was effectively decreased by 2b (42.65%), 2c (52.56%), and quercetin (33.48%) (data not shown).
Scheme 3.
Conclusions
Table 2 Radical scavenging activity of DHZ (1) and derivatives (2b–c) toward ABTS+ Compound
Imax
IC50 (lM)
n
1 2b 2c
96.6 ± 1.9 99.5 ± 0.8 99.6 ± 0.5
8.0 ± 1.0 8.0 ± 1.0 6.5 ± 0.5
6.3 6.3 7.8
Data are expressed as mean ± standard error (SE) of % maximal inhibition (Imax) and concentration required to scavenge 50% of DPPH (IC50); n = stoichiometric factor (equivalents of radicals quenched by 1 equiv of substrate).
significant increase in the ability of this structural class of compounds to inhibit lipid peroxidation. This is consistent with the observation that organoselenides in general are reactive toward peroxides and hydroperoxides.23 It is well established that the antioxidant activity of compounds in homogenous solutions may not be representative of their activity in heterogeneous media such as those found within cells and other in vivo environments.24 Consequently, we chose to explore the antioxidant activity of 1 and 2b–c in red blood cells (RBC) using the hemolysis model in order to further understand their biological
Two new organochalcogen-containing zingerone derivatives, 4-(4-hydroxy-3-methoxyphenyl)-4-(phenylseleno)-2-butanone (2b) and 4-(4-hydroxy-3-methoxyphenyl)-4-(phenylthio)-2-butanone (2c) were prepared and evaluated for their antioxidant properties. DPPH and lipid peroxidation studies showed that 2b and 2c have significantly improved antioxidant activity over dehydrozingerone (1), while an ABTS assay showed that all compounds have similar electron transfer capacity. We speculate that the improved activity of 2b and 2c is partly due to the ability of these compounds to act twice as phenolic antioxidants through a mechanism that eliminates phenylselenyl or phenylthiyl radicals. Acknowledgments This research was undertaken as part of the scientific activities of the international multidisciplinary SeS Redox and Catalysis network. We are grateful to CAPES, CNPq, FINEP, FAPERGS and the Australian Research Council (through the Centres of Excellence Scheme) for financial support.
Table 3 Antioxidant activity of DHZ (1) and derivatives (2b–c) against lipid peroxidation Concentration (lM)
Compound
1 2b 2c
10
50
100
500
85.1 ± 6.5 83.5 ± 5.8⁄ 98.4 ± 1.5
88.8 ± 8.8 52.7 ± 3.4⁄⁄⁄ 94.1 ± 3.6
88.5 ± 4.0 42.4 ± 6.5⁄⁄⁄ 80.6 ± 8.1⁄
86.4 ± 4.4 28.4 ± 3.0⁄⁄⁄ 57.6 ± 5.1⁄⁄
Imax
IC50 (lM)
12.1 ± 4.7 71.6 ± 5.3 42.4 ± 8.9
— 66.3 ± 3.6 —
Data are expressed as mean ± standard error (SE) of % lipid peroxidation. IC50 = concentration (lM) required to decrease 50% lipid peroxidation. Imax = % maximal inhibition. p <0.05. ⁄⁄p <0.01. ⁄⁄⁄p <0.001 when compared to control sample (SNP solution) by Student–Newman–Keuls test for post-hoc comparison.
⁄
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References and notes 1. (a) de Bernardi, M.; Vidari, G.; Vita-Finzi, P. Phytochemistry 1976, 15, 1785; (b) Connell, D. W.; Sutherland, M. D. Aust. J. Chem. 1969, 22, 1033. 2. Marchianni, A.; Mammi, S.; Siligardi, G.; Hussain, R.; Tessari, L.; Bubacco, L.; Delogu, G.; Fabbri, D.; Dettori, M. A.; Sanna, D.; Dedola, S.; Serra, P. A.; Ruzza, P. Amino Acids 2013, 45, 327. 3. (a) Baliga, M. S.; Haniadka, R.; Pereira, M. M.; Thilakchand, K. R.; Rao, S.; Arora, R. Food Funct. 2012, 3, 714; (b) Corrigan, D. In Adverse Effects of Herbal Drugs; de Smet, P. A. G. M., Keller, K., Hansel, R., Chandler, R. F., Eds.; Springer: Berlin, Heidelberg, 1997; vol. 3, pp 215–216. 4. (a) Kubra, I. R.; Bettadaiah, B. K.; Murthy, P. S.; Rao, L. J. M. J. Food Sci. Technol. 2014, 51, 245; (b) Kubra, I. R.; Murthy, P. S.; Rao, L. J. M. J. Food Sci. 2013, 78, M64; (c) Rao, M. C.; Sudheendra, A. T.; Nayak, P. G.; Paul, P.; Kutty, G. N.; Shenoy, R. R. Mol. Cell. Biochem. 2011, 355, 249; (d) Kabuto, H.; Nishizawa, M.; Tada, M.; Higashio, C.; Shishibori, T.; Kohno, M. Neurochem. Res. 2005, 30, 325; (e) Priyadarsini, K. I.; Devasagayam, T. P. A.; Rao, M. N. A.; Guha, S. N. Radiat. Phys. Chem. 1999, 54, 551; (f) Nugroho, A. E.; Yuniarti, N.; Estyastono, E. P.; Supardjan, ; Hakim, L. Majalah Farm. Ind. 2006, 17, 116; (g) Motohashi, N.; Takahashi, A.; Yamagami, C.; Saito, Y. Chem. Pharm. Bull. 2005, 53, 1003; (h) Priyadarsinia, K. I.; Guha, S. N.; Rao, M. N. A. Free Radical Biol. Med. 1998, 24, 933; (i) Kuo, P.-C.; Damu, A. G.; Cherng, C.-Y.; Jeng, J.-F.; Teng, C.-M.; Lee, E.-J.; Wu, T.-S. Arch. Pharm. Res. 2005, 28, 518; (j) Musialik, M.; Litwinienko, G. J. Therm. Anal. Calorim. 2007, 88, 781; (k) Motohashi, N.; Ashihara, Y.; Yamagami, C.; Saito, Y. Mutat. Res. 1997, 377, 17; (l) Tatsuzaki, J.; Bastow, K. F.; NakagawaGoto, K.; Nakamura, S.; Itokawa, H.; Lee, K.-H. J. Nat. Prod. 2006, 69, 1445; (m) Yogosawa, S.; Yamada, Y.; Yasuda, S.; Sun, Q.; Takizawa, K.; Sakai, T. J. Nat. Prod. 2012, 75, 2088; (n) Iwami, M.; Shiina, T.; Hirayama, H.; Shima, T.; Takewaki, T.; Shimizu, Y. J. Nat. Med. 2011, 65, 89. 5. (a) Schöneich, C. Exp. Gerontol. 1999, 34, 19; (b) Ueda, Y.; Uehara, N.; Sasaki, H.; Kobayashi, K.; Yamakawa, T. Plant Physiol. Biochem. 2013, 70, 396; (c) Rico, D.; Martín-González, A.; Díaz, S.; Lucas, P.; Gutiérrez, J.-C. Comp. Biochem. Physiol. 2009, 149, 90; (d) Yamamori, T.; Yasui, H.; Yamazumi, M.; Wada, Y.; Nakamura, Y.; Nakamura, H.; Inanami, O. Free Radical Biol. Med. 2012, 53, 260. 6. Sies, H. Angew. Chem., Int. Ed. Engl. 1986, 25, 1058. 7. (a) Agarwal, A.; Saleh, R. A.; Bedaiwy, M. A. Fertil. Steril. 2003, 79, 829; (b) AlGuborya, K. H.; Fowlerb, P. A.; Garrelc, C. Int. J. Biochem. Cell Biol. 2010, 42, 1634; (c) Taylor, C. T. Environ. Toxicol. Pharmacol. 2001, 10, 189; (d) Bennett, S.; Grant, M. M.; Aldred, S. J. Alzheimers Dis. 2009, 17, 245; (e) Reuter, S.; Gupta, S. C.; Chaturvedi, M. M.; Aggarwal, B. B. Free Radical Biol. Med. 2010, 49, 1603. and references therein. 8. (a)PATAI’s Chemistry of Functional Groups: Organic Selenium and Tellurium Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: Chichester, 2013; (b) Wirth, T. Organoselenium Chemistry: Synthesis and Reactions; Wiley-VCH: Weinheim, 2011; (c) Liotta, D. Organoselenium Chemistry; Wiley: New York, 1987; (d) Back, T. G. Organoselenium Chemistry: A Practical Approach; Oxford University Press: Oxford, 1999; (e) Perin, G.; Lenardão, E. J.; Jacob, R. G.; Panatieri, R. B. Chem. Rev. 2009, 109, 1277; (f) Freudendahl, D. M.; Santoro, S.; Shahzad, S. A.; Santi, C.; Wirth, T. Angew. Chem., Int. Ed 2009, 48, 8409; (g) Santi, C.; Santoro, S.; Battistelli, B. Curr. Org. Chem. 2010, 14, 2442. 9. (a) Nogueira, C. W.; Zeni, G.; Rocha, J. B. T. Chem. Rev. 2004, 104, 6255; (b) Prigol, M.; Nogueira, C. W.; Zeni, G.; Bronze, M. R.; Constantino, L. Chem.-Biol. Interact. 2012, 200, 65; (c) Tapiero, H.; Townsend, D. M.; Tew, K. D. Biomed. Pharmacother. 2003, 57, 134; (d) Arteel, G. E.; Sies, H. Environ. Toxicol. Pharmacol. 2001, 10, 153; (e) Engman, L.; Laws, M. J.; Malmström, J.; Schiesser, C. H.; Zugaro, L. M. J. Org. Chem. 1999, 64, 6764. 10. For examples: (a) Sartori, G.; Neto, J. S. S.; Pesarico, A. P.; Back, D. F.; Nogueira, C. W.; Zeni, G. Org. Biomol. Chem. 2013, 11, 1199; (b) Storkey, C.; Pattison, D. I.; White, J. M.; Schiesser, C. H.; Davies, M. J. Chem. Res. Toxicol. 2012, 25, 2589; (c) Savegnago, L.; Vieira, A. I.; Seus, N.; Goldani, B. S.; Castro, M. R.; Lenardão, E. J.; Alves, D. Tetrahedron Lett. 2013, 54, 40. 11. (a) Choi, S. K. Synthetic Multivalent Molecules; Wiley-Interscience: New York, 2004; (b) Bastow, K. F.; Wang, H. K.; Cheng, Y. C.; Lee, K. H. Bioorg. Med. Chem. 1997, 5, 1481; (c) Chang, J. Y.; Guo, X.; Chen, H. X.; Jiang, Z.; Fu, Q.; Wang, H. K.; Bastow, K. F.; Zhu, X. K.; Guan, J.; Lee, K. H.; Cheng, T. C. Biochem. Pharm. 2000, 59, 497; (d) Shi, Q.; Wang, H. K.; Bastow, K. F.; Tachibana, Y.; Chen, K.; Lee, F. Y.; Lee, K. H. Bioorg. Med. Chem. 2001, 9, 2999; (e) Ohtsu, H.; Nakanishi, Y.; Bastow, K. F.; Lee, F. Y.; Lee, K. H. Bioorg. Med. Chem. 2003, 11, 1851; (f) Nakagawa-Goto, K.; Nakamura, S.; Bastow, K. F.; Nyarko, A.; Peng, C. Y.; Lee, F. Y.; Lee, F. C.; Lee, K. H. Bioorg. Med. Chem. Lett. 2007, 17, 2894; (g) Tatsuzaki, J.; Taniguchi, M.; Bastow, K. F.; Nakagawa-Goto, K.; Morris-Natschke, S. L.; Itokawa, H.; Baba, K.; Lee, K. H. Bioorg. Med. Chem. 2007, 15, 6193; (h) Nakagawa-Goto, K.; Yamada, K.; Nakamura, S.; Chen, T.-H.; Chiang, P.-C.; Bastow, K. F.; Wang, S. C.; Spohn, B.; Hung, M. C.; Lee, F. Y.; Lee, F. C.; Lee, K. H. Bioorg. Med. Chem. Lett. 2007, 17, 5204; (i) Grange, R. L.; Ziogas, J.; North, A. J.; Angus, J. A.; Schiesser, C. H. Bioorg. Med. Chem. Lett. 2008, 18, 1241; (j) Aumann, K. M.; Scammells, P. J.; White, J.
12.
13.
14.
15.
16.
17. 18.
19. 20. 21. 22. 23. 24. 25.
M.; Schiesser, C. H. Org. Biomol. Chem. 2007, 5, 1276; (k) Ashton, T. D.; Aumann, K. M.; Baker, S. P.; Schiesser, C. H.; Scammells, P. J. Bioorg. Med. Chem. Lett. 2007, 17, 6779; (l) Staples, M. K.; Grange, R. L.; Angus, J. A.; Ziogas, J.; Tan, N. P. H.; Tayloe, M. K.; Schiesser, C. H. Org. Biomol. Chem. 2011, 9, 473. (a) Lenardão, E. J.; Jacob, R. G.; Mesquita, K. D.; Lara, R. G.; Webber, R.; Martinez, D. M.; Savegnago, L.; Mendes, S. R.; Alves, D.; Perin, G. Green Chem. Lett. Rev. 2013, 6, 269; (b) Victoria, F. N.; Radatz, C. S.; Sachini, M.; Jacob, R. G.; Alves, D.; Savegnago, L.; Perin, G.; Motta, A. S.; Silva, W. P.; Lenardão, E. J. Food Control 2012, 23, 95; (c) Victoria, F. N.; Anversa, R. G.; Penteado, F.; Castro, M.; Lenardão, E. J.; Savegnago, L. Eur. J. Pharm. 2014, 742, 131. Sala, G. S.; Lattanzi, A. C-Other Atom Bond Formation (S, Se, B) in Stereoselective Organocatalysis: Bond Formation Methodologies and Activation Modes; WileyBlackwell: Southampton, 2013. 493–523. (a) Ba˘doiu, A.; Bernardinelli, G.; Besnard, C.; Kündig, E. P. Org. Biomol. Chem. 2010, 8, 193; (b) Perin, G.; Mesquita, K.; Calheiro, T. P.; Silva, M. S.; Lenardão, E. J.; Alves, D.; Jacob, R. G. Synth. Commun. 2014, 44, 49; (c) Lenardão, E. J.; Trecha, D. O.; Ferreira, P. C.; Jacob, R. G.; Perin, G. J. Braz. Chem. Soc. 2009, 20, 93. (a) Miyashita, M.; Yoshikoshi, A. Synthesis 1980, 664; (b) Perin, G.; Borges, E. L.; Rosa, P. C.; Carvalho, P. N.; Lenardão, E. J. Tetrahedron Lett. 2013, 54, 1718; (c) Battistelli, B.; Lorenzo, T.; Tiecco, M.; Santi, C. Eur. J. Org. Chem. 2011, 10, 1848. Synthetic procedure: 4-(4-Hydroxy-3-methoxyphenyl)-4-(phenylseleno)-2butanone (2b): To a solution of diphenyl diselenide (0.312 g, 1.0 mmol) in ethanol (2.5 mL) under a N2 atmosphere, NaBH4 (0.049 g, 1.3 mmol) was added at room temperature and the mixture stirred for 30 min. The colorless (or faint yellow) solution of benzeneselenolate obtained was cooled to 0 °C in an ice bath and acetic acid (2.3 mmol) was added. A solution of DHZ 1 (0.192 g, 1.0 mmol) in ethanol (0.5 mL) was then added and the resulting mixture stirred at 0 °C for 4 h. After consumption of the starting materials (TLC), the mixture was diluted with ethyl acetate (15 mL) and washed with water (15 mL) and brine (3 15 mL). The organic phase was dried (MgSO4) and then concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel using ethyl acetate/hexane (30% v/v) as the eluent, yielding the product as a pale yellow solid. Yield: 0.074 g, 21%, mp 82– 85 °C, 1H NMR (400 MHz, CDCl3): d = 7.48–7.19 (m, 5H), 6.93–6.56 (m, 3H), 5.77 (br s, 1H), 4.73 (dd, J = 6.3 and 8.7 Hz, 1H), 3.75 (s, 3H), 3.19 (dd, J = 8.7 and 16.9 Hz, 1H), 3.02 (dd, J = 6.3 and 16.9 Hz, 1H), 2.04 (s, 3H). 13C NMR (100 MHz, CDCl3) d 205.8, 146.2, 144.8, 134.0, 132.9, 132.7, 128.8, 127.5, 120.2, 114.2, 110.4, 55.8, 49.7, 47.9, 30.7. IR (KBr pellet), m (cm1): 1276.9, 1514.1, 1689.6, 2968.4, 3361.9. MS (relative intensity) m/z: 194 (M+SePh, 5.5), 193 (43.9), 192 (34.5), 177 (35.8), 158 (26.5), 151 (15.9), 150 (21.4), 145 (63.1), 135 (18.4), 117 (28.0), 111 (12.3), 109 (11.3), 97 (23.2), 95 (19.3), 83 (25.3), 81 (26.3), 78 (70.6), 69 (38.7), 67 (17.9), 57 (40.5), 55 (37.7), 43 (100). HRMS (ES) for C17H18O3Se+Na ([M+Na]+): calcd: 373.0313; found: 373.0309. Günther, W. H. H. J. Org. Chem. 1966, 31, 1202. Synthetic procedure: 4-(4-Hydroxy-3-methoxyphenyl)-4-(phenylthio)butan-2one (2c). To a round-bottomed flask containing mixture of benzenephenol (0.065 g, 0.6 mmol) and KF/Al2O3 (0.07 g) in glycerol (1.0 mL) was added DHZ (1a, 0.058 g, 0.3 mmol). The reaction mixture was stirred at 90 °C for 4 h under a N2 atmosphere. After completion of the reaction (TLC), the mixture was cooled to room temperature, diluted with ethyl acetate (15 mL) and washed with aq NH4Cl (3 15 mL). The solvent was evaporated under reduced pressure and the residue was purified by column chromatography over silica gel eluting with hexane/ethyl acetate (20% v/v) yielding the product as a white solid. Yield: 0.078 g, 86%. White solid, mp 78–80 °C, 1H NMR (400 MHz, CDCl3): d = 7.34–7.24 (m, 5H), 6.64–6.77 (m, 3H), 5.71 (br s, 1H), 4.68 (dd, J = 6.6 and 8.1 Hz, 1H), 3.83 (s, 3H), 3.08 (dd, J = 16.8 and 8.1 Hz, 1H), 3.00 (dd, J = 16.8 and 6.6 Hz, 1H), 2.09 ppm (s, 3H). 13C NMR (100 MHz, CDCl3) d (ppm) 205.9, 146.4, 144.9, 134.1, 133.0, 132.8, 128.9, 127.6, 120.3, 114.3, 110.5, 55.9, 49.7, 48.0, 30.8. IR (KBr pellet), m (cm1): 1282.7, 1515.1, 1689.7, 2960.8, 3362.9. MS (relative intensity) m/z: 302 (M+, 0.2), 194 (5.1), 193 (42.0), 177 (2.0), 151 (10.6), 145 (3.0), 135 (5.5), 119 (1.4), 110 (5.5), 107 (2.4), 91 (2.1), 77 (4.3), 65 (3.1), 43 (100.0). HRMS (ES) for C17H18O3S+Na ([M+Na]+): calcd: 325.0869; found: 325.0874. Amarowicz, R.; Pegg, R. B.; Rahimi-Moghaddam, P.; Barl, B.; Weil, J. A. Food Chem. 2004, 84, 551. Re, R.; Pellegrini, N.; Proteggente, A.; Pannala, M.; Yang, M.; Rice-Evans, C. Free Radical Biol. Med. 1999, 26, 1231. Valko, M.; Leibfritz, D.; Moncol, J.; Cronin, T. D. M.; Mazur, M.; Telser, J. Int. J. Biochem. Cell Biol. 2007, 39, 44. Choi, C. W.; Kim, S. C.; Hwang, S. S.; Choi, B. K.; Ahn, H. J.; Lee, M. Y.; Park, S. H.; Kim, S. K. Plant Sci. 2002, 163, 1161. For a review, see: Alberto, E. E.; do Nascimento, V.; Braga, A. L. J. Braz. Chem. Soc. 2010, 21, 2032. Zhou, B.; Miao, Q.; Yang, L.; Liu, Z. L. Chem.-Eur. J. 2005, 11, 680. Banerjee, A.; Kunwar, A.; Mishra, B.; Priyadarsini, K. I. Chem.-Biol. Interact. 2008, 174, 134.