Research article Received: 17 November 2013,
Revised: 31 March 2014,
Accepted: 05 April 2014
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.2701
Fluorescent studies on the interaction of DNA and ternary lanthanide complexes with cinnamic acid-phenanthroline and antibacterial activities testing Hui-Juan Sun,† Ai-Ling Wang,† Hai-Bin Chu* and Yong-Liang Zhao* ABSTRACT: Twelve lanthanide complexes with cinnamate (cin–) and 1,10-phenanthroline (phen) were synthesized and characterized. Their compositions were assumed to be RE(cin)3phen (RE3+ = La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Tm3+, Yb3+, Lu3+). The interaction mode between the complexes and DNA was investigated by fluorescence quenching experiment. The results indicated the complexes could bind to DNA and the main binding mode is intercalative binding. The fluorescence quenching constants of the complexes increased from La(cin)3phen to Lu(cin)3phen. Additionally, the antibacterial activity testing showed that the complexes exhibited excellent antibacterial ability against Escherichia coli, and the changes of antibacterial ability are in agreement with that of the fluorescence quenching constants. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: lanthanide complexes; cinnamic acid; 1,10-phenanthroline; DNA-binding; antibacterial activities
Introduction Recently, due to potential applications of metal complexes as anticancer drugs or as complexes with other biological functions, more attention has been paid for the interactions of metal complexes with nucleic acids (1). In addition, the interactions of the complexes with DNA depend on the mode and the affinity between the complexes and DNA (2–6). Generally, these interactions primarily involve three binding modes: intercalative, groove and electrostatic (7). The intercalative binding is stronger than other two binding modes because the surface of intercalative molecule is sandwiched between the aromatic heterocyclic base pairs of DNA (8,9). Cinnamic acid (Hcin) is a compound that can be found in plants, especially in flavorings and products containing cinnamon oil (10). Hcin and its derivates are described to possess a broad therapeutic action, including antimicrobial activity (11) and antifungal activity (12). Hcin has been widely used in medicines, pesticides, plastic, preservatives, food flavors, photosensitive resins, local anesthetics and fungicides (10,13–15). It exhibits superior antitumor activity against human malignant tumors, and can inhibit tumorous proliferation and induce its differentiation (16,17). Lanthanide complexes have shown unique biological activities (18,19). Polypyridine ligands (such as 2,2′-bipyridine, 1,10-phenanthroline [phen]) also have some antibacterial activities (20). Lanthanide complexes with two or more bioactive functional groups are likely to be anticarcinogens, which are less toxic, more efficient and more economical compared with the single functional group compounds. Synthesis and characterization of lanthanide complexes with cin– ions and phen as ligands have been studied (21), but there are few reports about their DNA-binding and antibacterial properties. Herein, 12 lanthanide complexes with cin– ion as anion ligand and phen as neutral ligand were synthesized and characterized. The properties of DNA binding with these
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complexes were studied using fluorescence spectroscopy with a view to evaluating their pharmaceutical activities. Antibacterial activities of the complexes also were investigated and the antimicrobial activities of the complexes are stronger than those of ligands and lanthanide ions, respectively.
Materials and methods Materials and general methods Calf thymus DNA (Sigma Chemical Co., St. Louis, MO, USA), tris (hydroxymethyl) aminomethane hydrochloride and ethidium bromide (EB) are used as received. Purities of rare earth oxides are 99.99%. Other reactants and solvents are all of analytical grade if not mentioned. Elemental analysis of C, H and N was performed with a Vario EL Cube elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). The molar concentration of rare earth was determined by EDTA titration method with xylenol orange as indicator in hexamethylenetetramine-HCl buffer solution. Molar conductivity was measured by DDSJ-308A conductivity meter at 25° C with N,N-dimethylformamide (DMF) as solvent and the concentration of complexes was 1.0 × 10–3 mol/L. Infrared spectra were recorded on a Nicolet Nexus 670 Fourier transform-infrared * Correspondence to: H.-B. Chu and Y.-L. Zhao, College of Chemistry and Chemical Engineering, Inner Mongolia University, Huhhot, 010021, China. E-mail: [email protected]; [email protected] †
These authors contributed equally to this work. College of Chemistry and Chemical Engineering, Inner Mongolia University, Huhhot, 010021, China
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H.-J. Sun et al. spectrometer (Nicolet Instrument Inc., Madison, WI, USA) using KBr pellet. The thermogravimetric (TG) analysis and differential scanning calorimetry were performed by a NETZSCHSTA 409 PC instrument (NETZSCH GmbH & Co., Selb, Germany) with a heating rate of 10 ºC/min under an air atmosphere. Absorption spectra were recorded on a Tu-1901 spectrophotometer (Beijing Purkinje General Instrument Co. Ltd., Beijing, China), by dissolving the complexes in DMF and diluted to 1.0 × 10–5 mol/L using absolute ethanol. Fluorescence quenching experiments were carried on the Shimadzu RF5301PC spectrophotometer (Shimadzu Corp., Kyoto, Japan) with excitation and emission slit width were 10.0 nm at room temperature.
Preparation of lanthanide complexes Preparation of rare earth chloride. Rare earth oxides were dissolved in a certain amount of hydrochloric acid. The mixture was heated until crystallized film appeared above the solution, after which the mixture was cooled to room temperature. A white powdered solid appeared. The powder was dissolved in anhydrous ethanol (22). Preparation of rare earth complexes. Phen 0.5 mmol was dissolved in anhydrous ethanol, and then an aqueous solution of 1.5 mmol sodium cinnamate (C6H5CH=CHCOONa) was added. A few minutes later, 0.5 mmol LaCl3 was added dropwise in to this mixture with continuous stirring under constant temperature of 60°C. The pH value of the solution was adjusted to 6.8 with NH3·H2O. After stirring at 60°C for 3 h, the solution was left still overnight at room temperature. The precipitate was separated by filtering and washing with anhydrous ethanol. Dried at 50°C for several hours, the complex La(cin)3phen was obtained. Other 11 complexes were prepared in a similar way.
solutions of the lanthanide complexes (1.0 × 10–3 mol/L) were prepared by dissolving the complexes in DMF and diluted to 1.0 × 10–5 mol/L by doubly distilled water. EB stock solution was prepared by dissolving its crystal in doubly distilled water according to CDNA/CEB = 20. Test of antibacterial activity In vitro antibacterial activity of the ligands and the complexes against Escherichia coli was studied by using the filter paper disc diffusion method (25,26). The E. coli was spread on sterile Luria-Bertani agar plates by using a sterile cotton swab. Six mm diameter sterile filter papers were taken and coated with 20 μL 0.004, 0.008 and 0.012 mol/L solution of Hcin, phen and the 12 complexes in DMF respectively, which were placed at the center of the lawn carefully without touching the other parts. Flat plates were incubated at 37°C for 16–18 h. Their inhibition diameters (including filter paper) were measured with a Vernier caliper. All experiments were carried out in parallel three times and the average diameter values were calculated.
Results and discussion Characterization of the complexes
Preparation of calf thymus DNA solution and ethidium bromide solution
Composition analysis and molar conductivity. The data of elemental analyses (C, H and N) and rare earth EDTA titration of the complexes are shown in Table 1. The results indicated that the composition of the complexes are RE(cin)3phen (RE3+=La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Tm3+, Yb3+, Lu3+). The molar conductance values of these complexes in DMF are in the range 14.1–28.9 S·cm2/mol. These small values indicated that only a small section of rare earth complexes ionize in DMF solution and these complexes are non-electrolytes (27,28).
The stock solution of calf thymus DNA was prepared by dissolving appropriate solid DNA into doubly distilled water and stored at 4°C. The concentration of DNA in stock solution was determined by ultraviolet (UV) absorption at 260 nm using a molar absorption coefficient ε260 = 6600 L/mol·per cm (23). The purity of the DNA was checked by monitoring the ratio of the absorbance at 260 nm to that at 280 nm. The solution gave a ratio of 1.8–2.0 at A260/A280, indicating that DNA was sufficiently free from protein (24). The stock
Thermogravimetric analysis–differential scanning calorimetry. The TG analysis and differential scanning calorimetry of some the complexes was studied and it was found that the thermal behaviors of the complexes are quite similar. During the heating of the complexes, the TG curves underwent a series of thermal changes associated with weight loss of the samples. As shown in Fig. 1, the Sm(cin)3phen complex begins to decompose at about 300ºC with obvious weight loss. The weight loss of the
Table 1. Composition analysis and molar conductivities (S·cm2/mol) of the lanthanide complexes Complexes La(cin)3phen Pr(cin)3phen Nd(cin)3phen Sm(cin)3phen Eu(cin)3phen Gd(cin)3phen Tb(cin)3phen Dy(cin)3phen Ho(cin)3phen Tm(cin)3phen Yb(cin)3phen Lu(cin)3phen
C% 61.16 (61.59) 61.09 (61.43) 60.61 (61.16) 60.52 (60.68) 60.02 (60.55) 59.86 (60.14) 59.68 (60.01) 59.27 (59.74) 59.12 (59.55) 58.82 (59.25) 59.06 (58.94) 58.34 (58.80)
H% 3.894 3.893 3.864 3.454 3.960 3.836 3.808 3.773 3.761 3.666 3.300 3.683
(3.84) (3.83) (3.82) (3.79) (3.78) (3.75) (3.74) (3.73) (3.72) (3.70) (3.68) (3.67)
N% 3.57 3.65 3.65 3.67 4.05 3.15 3.12 3.41 3.54 3.49 3.30 3.27
(3.68) (3.67) (3.66) (3.63) (3.62) (3.60) (3.59) (3.57) (3.56) (3.54) (3.52) (3.52)
RE % 18.31 18.46 18.90 19.59 19.58 20.56 20.63 21.01 20.96 21.78 22.03 22.27
(18.26) (18.48) (18.83) (19.48) (19.64) (20.19) (20.36) (20.72) (20.97) (21.37) (21.77) (21.96)
Λm 28.6 28.9 27.1 27.2 27.9 28.1 28.3 26.9 18.4 16.5 14.2 14.1
The values in brackets are theoretical values.
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Spectra on the interaction and antibacterial activities testing Ultraviolet-visible absorption spectra. The UV-visible absorption spectra of ligands phen, Hcin and all complexes were determined with a mixture solution (DMF–absolute ethanol = 1 : 5) as reference in the range 200–400 nm. As shown in Fig. 3, free ligands (Hcin and phen) and the complex Nd(cin)3phen show strong absorption. The band of Hcin shifted from 270 nm to 266 nm in the complex, which indicated that the rare earth ions coordinated with cin–. It also can be seen that the absorption band of phen at 264 nm shifted to 266 nm after being coordinated in the complexes, indicating that the ligand phen was involved in the coordination. Moreover, the λmax of the complex is near to that of phen, which may due to the π–π* transition energy of phen is much stronger than that of Hcin (32). Interactions of the complexes with DNA Figure 1. TG-DSC curves of Sm(cin)3phen. DSC, differential scanning calorimetry; TG, thermogravimetric.
complex about 308ºC is 23.64%, which could be assigned to the theoretical content of the complex containing one phen (23.34%). The weight loss of 56.96% at about 473ºC is consistent with the theoretical value of losing three cin– ions (57.18%). Of the initial mass of the sample 23.71% was left as a residue of 1/2Sm2O3 (calculated 22.58%). Infrared spectra. In the range 4000–400/cm, the infrared spectra of ligands phen, Hcin and all the complexes were determined, some of which are given in Fig. 2. The peaks at 1685/cm, 1283/cm and 1402/cm could be attributed to the ν(C=O) vibration, δO-H rocking vibration and ν(C-O) vibration of ligand Hcin, which disappeared after the formation of the complexes. Two new peaks emerged at 1406/cm and 1582/cm, which could be assigned to the symmetric and antisymmetric stretching vibrations of the carboxylate group, respectively. In addition, a new peak appeared in the region 482–485/cm could be attributed to the RE-O absorption peak. These changes indicated that the carboxyl coordinate with the rare earth ions in the complexes (29,30). After introducing the neutral ligands, the ν(C=N) of phen at 1587/cm shifted to near 1568/cm in the complexes, which revealed that the two nitrogen atoms of phen coordinated to the rare earth ions and formed a chelate ring (31).
Figure 2. Infrared spectra of ligands and some complexes: (a) Hcin; (b) phen; (c) La(cin)3phen; (d) Tb(cin)3phen; (e) Tm(cin)3phen.
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The fluorescence spectra of DNA-EB solution (1.0 mL 1.0 × 10–5 mol/L DNA and 1.0 mL 5.0 × 10–7 mol/L EB) were recorded with increasing amounts of rare earth complex (1.0 × 10–3 mol/L, 10 μL each time). The excitation wavelength was selected as 537 nm and the emission spectra were recorded from 570 nm to 630 nm. The DNA-EB system has a characteristic emission band around 592 nm. Fig. 4 showed the emission spectra of the DNA-EB system in the absence and presence of the Pr(cin) 3phen complex, when the solution of Pr(cin)3phen was added, the fluorescence intensity of the DNA-EB solution was gradually weakened with increasing amounts of the complex. Here EB has been employed in the examination of the reaction, as EB presumably binds initially to DNA by intercalation (33). It suggested that Pr(cin)3phen substituted for EB from the binding sites in the DNA-EB system, which led to a large decrease in the emission intensity of the DNA-EB system after adding the complex solution. Besides, the control experiment showed that the presence of lanthanide complexes would not decrease the fluorescence intensity of EB without DNA. Therefore, the results indicated that the complexes had a strong interaction with DNA, and the major binding mode was intercalative binding. This binding mode has been observed in some instances (34,35). The quenching plots illustrated that the quenching of EB bound to DNA by the complex is a good agreement with the linear Stern–Volmer equation (36):
Figure 3. Ultraviolet spectra of the ligands and complex: (a) Hcin; (b) phen; (c) Nd –5 (cin)3phen. The concentrations are all 1 × 10 mol/L.
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H.-J. Sun et al. the intercalative binding of the complexes to DNA bases (38–40). The changes in relative viscosity of DNA solution with increasing concentrations of Pr(cin)3phen were also observed. The value of relative viscosity enhanced with increasing the amounts of the complex further suggested that the interaction mode of the complexes with DNA should be intercalation binding (41,42).
Antibacterial activity of ligands and complexes
Figure 4. Effect of Pr(cin)3phen on the fluorescence spectra of ethidium bromide–DNA system. Arrow shows the intensity changes as increasing amounts of the complex. The inset is Stern–Volmer quenching curves.
F 0 =F ¼ 1 þ K q ½Q
Where F0 is the emission intensity in the absence of quencher (complex), F is the emission intensity in the presence of quencher, Kq is the quenching constant and [Q] is the concentration of the quencher. Plots of F0/F versus [Q] should appear to be linear. Taking Pr(cin)3phen as example, Kq is obtained from the slope of the F0/F versus (DNA) linear plot (inset of Fig. 4), and is found to be 3.13 × 104 mol/L, which indicate a strong interaction of lanthanide complex with DNA. The data of the fluorescence quenching constants were presented in Table 2. It can be seen when the lanthanide ion radius decreases, the corresponding ternary complex gets a higher fluorescence quenching constant. The data suggest that the binding ability of Lu(cin)3phen is the highest and La(cin)3phen is the lowest. The Lu3+ has the smallest ion radius, the biggest charge density and, thus, the strongest electrostatic interaction with DNA in these complexes. Consequently, the capacity of phen in Lu(cin)3phen inserting into the base pairs of DNA is the strongest and the fluorescence quenching constant is the biggest (37). On the contrary, the capacity of La(cin) 3phen inserting into the base pairs is the weakest and the fluorescence quenching constant is the smallest. To investigate further whether the interactions between DNA and lanthanide complexes involved intercalation, the interaction between the rare earth complexes and calf thymus DNA was investigated using UV-visible spectrophotometry and viscosity measurement. As the DNA concentration increased, the absorption spectra of Sm(cin)3phen, Gd(cin)3phen and Lu(cin)3phen showed clear hypochromicity at the maximum of 266 nm, together with a red shift of about 2.5 nm. The hypochromicity and red shift in the absorption spectra of the complexes proved
The antibacterial activity of the ligands and some complexes were evaluated by the flat-filter paper method against strains belonging to E. coli. Fig. 5 shows the antibacterial ring of the ligands and Lu (cin)3phen with different concentrations on E. coli. The concentrations of the complex and ligands are: (1) 0.004 mol/L Lu(cin)3phen; (2) 0.008 mol/L; Lu(cin)3phen; (3) 0.012 mol/L Lu(cin)3phen; (4) 0.012 mol/L phen; (5) 0.012 mol/L Hcin; and (6) DMF, respectively. The antibacterial activities of the complexes expressed as the diameter of growth inhibition area in millimeters are listed in Table 3. From Table 3 and Fig. 5, the following conclusions are obtained. First, all these complexes exhibited a stronger inhibitory effect on the E. coli than the ligands. Second, the antibacterial activities of the lanthanide complexes enhanced with the increasing concentration of the complexes. Third, the antimicrobial activities of higher molecular weight rare earth complexes are greater than the lower molecular weight rare earth complexes. The antibacterial mechanism is presumably that the complexes affect the functions associated with cell division of fungi such as cell wall, protein and/or DNA biosyntheses or kill the exponentially growing cells (26,43). Besides, as proven by the preliminary test (MTT method), some have the ability to kill leukemia cancer cells and cervical cancer cells.
Figure 5. Antibacterial ring of ligands and Lu(cin)3phen with different concentrations on E. coli.
Table 2. Fluorescence quenching constants of the complexes interaction with DNA Complexes
La(cin)3phen
Pr(cin)3phen
Nd(cin)3phen
Sm(cin)3phen
Eu(cin)3phen
Gd(cin)3phen
Kq (mol/L) Complexes Kq (mol/L)
2.50 × 104 Tb(cin)3phen 4.98 × 104
3.13 × 104 Dy(cin)3phen 5.12 × 104
3.90 × 104 Ho(cin)3phen 5.81 × 104
4.17 × 104 Tm(cin)3phen 6.49 × 104
4.41 × 104 Yb(cin)3phen 6.51 × 104
4.88 × 104 Lu(cin)3phen 7.12 × 104
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Spectra on the interaction and antibacterial activities testing Table 3. Inhibition zone diameter of the ligands and complexes/mm Concentration Compounds N,N-dimethylformamide Hcin Phen Pr(cin)3phen Sm(cin)3phen Eu(cin)3phen Gd(cin)3phen Dy(cin)3phen Lu(cin)3phen
0.004 mol/L
0.008 mol/L
0.012 mol/L
< 10 – < 10 13.9 15.8 16.5 16.5 18.5 18.9
< 10 – < 10 16.2 17.1 17.4 17.8 18.9 19.3
< 10 < 10 14 20.4 21.6 21.7 22.0 22.7 23.5
Conclusions In summary, 12 ternary lanthanide complexes with cin– as anion ligand and phen as neutral ligand have been prepared and characterized. To evaluate further their potential pharmaceutical activities, the DNA binding properties and antibacterial abilities were investigated by fluorescence quenching spectra and the flat-filter paper method. It was found that the 12 complexes could bind to DNA. The mainly interaction modes are found to be intercalative. The fluorescence quenching constants suggest that the binding ability of Lu(cin)3phen is the highest and La (cin)3phen is the lowest. According to the antibacterial testing results, all these complexes exhibit excellent antibacterial ability against E. coli and the complexes have stronger antibacterial abilities than each ligand and rare earth ions. These complexes may find applications in antibacterial agents, antitumor drugs and other related fields. Acknowledgments The research work is supported by the National Natural Science Foundation of China (21161013), Natural Science Foundation of Inner Mongolia (2011MS0202) and the Opening Foundation for Significant Fundamental Research of Inner Mongolia (2010KF03).
References 1. Rauf S, Gooding JJ, Akhtar K, Ghauri MA, Rahman M, Anwar MA, et al. Electrochemical approach of anticancer drugs-DNA interaction. J Pharm Biomed Anal 2005;37:205–17. 2. Nagane R, Koshigoe T, Chikira M. Interaction of Cu (II)-Arg-Gly-His-Xaa metallopeptides with DNA: effect of C-terminal residues, Leu and Glu. J Inorg Biochem 2003;93:204–12. 3. Zeng YB, Yang N, Liu WS, Tang N. Synthesis, characterization and DNA-binding properties of La(III) complex of chrysin. J Inorg Biochem 2003;97:258–64. 4. Silvestri A, Barone G, Ruisi G, Lo Giudice MT, Tumminello S. The interaction of native DNA with iron(III)-N,N′-ethylene-bis(salicylideneiminato)chloride. J Inorg Biochem 2004;98:589–94. 5. Mansouri-Torshizi H, I-Moghaddam M, Divsalar A, Saboury AA. 2,2′Bipyridinebutyldithiocarbamatoplatinum(II) and palladium(II) complexes: synthesis, characterization, cytotoxicity, and rich DNA-binding studies. Bioorgan Med Chem 2008;16:9616–25. 6. Sahoo BK, Ghosh KS, Bera R, Dasgupta S. Studies on the Interaction of diacetylcurcumin with calf thymus-DNA. Chem Phys 2008;351:163–9. 7. Tjahjono DH, Akutsu T, Yoshioka N, Inoue H. Cationic porphyrins bearing diazolium rings: synthesis and their interaction with calf thymus DNA. Biochim Biophys Acta 1999;1472:333–43.
Luminescence 2014
8. Ling LS, He ZK, Chen F, Zeng YE. Single-mismatch detection using nucleic acid molecular “light switch”. Talanta 2003;59:269–75. 9. He XQ, Lin QY, Hu RD, Lu XH. Synthesis, characterization and DNAbinding studies on La(III) and Ce(III) complexes containing ligand of N-phenyl-2-pyridinecarboxamide. Spectrochim Acta A 2007;68:184–90. 10. Hoskins JA. The occurrence, metabolism and toxicity of cinnamic acid and related compounds. J Appl Toxicol 1984;4:283–92. 11. Ramanan PN, Rao MN. Antimicrobial activity of cinnamic acid derivates. Ind J Exp Biol 1987;25:42–3. 12. Tawata S, Taira S, Kobamoto N, Zhu J, Ishihara M, Toyama S. Synthesis and antifungal activity of cinnamic acid esters. Biosci Biotechnol Biochem 1996;60:909–10. 13. Marques LF, Junior AABC, Correa CC, Lahoud MG, Silva RRD, Ribeiro SJL, et al. First crystal structures of lanthanide-hydrocinnamate complexes: Hydrothermal synthesis and photophysical studies. J Photochem Photobiol A 2013;252:69–76. 14. Raskin I. Role of salicylic acid in plants. Annu Rev Plant Physiol Plant Mol Biol 1992;43:439–63. 15. Liu L, Hudgins WR, Shack S, Yin MQ, Samid D. Cinnamic acid: a natural product with potential use in cancer intervention. Int J Cancer 1995;62:345–50. 16. Opdyke DLJ. Monographs on fragrance raw materials. Food Cosmet Toxicol 1975;13:687–90. 17. Yen GC, Chen YL, Sun FM, Chiang YL, Lu SH, Weng CJ. Accomparative study on the effectiveness of cis- and trans- form of cinnamic acid treatments for inhibiting invasive activity of human lung adenocarcinoma cells. Eur J Pharm Sci 2011;44:281–7. 18. Zhang YH. Cinnamic acid and its derivatives with tumor. Cancer Res Clin 2001;13:353–5. 19. Wang Q, Yang Z, Qi GF, Qin DD. Synthesis, crystal structure, antioxidant activities and DNA-binding studies of the Ln (Ш) complexes with 7-methoxychromone-3-carbaldehyde-(4′-hydroxy) benzoyl hydrazine. Eur J Med Chem 2009;44:2425–33. 20. Khan IM, Ahmad A, Aatif M. Synthesis, single-crystal characterization, antimicrobial activity and remarkable in vitro DNA interaction of hydrogen-bonded proton-transfer complex of 1,10-phenanthroline with 2,4,6-trinitrophenol. J Photochem Photobiol B 2011;105:6–13. 21. Zhao YL, Lian XS, Wu YM. Synthesis of ternary solid complexes of cinnamic acid-o-phenanthroline. Acta Sci Nat Univ NeiMenggu 1993;24:553–4. 22. Huang CH. Coordination Chemistry of Rare Earth. Science Press, Beijing, 1997. 23. Huang CZ, Li YF, Feng P. A spectrophotometric study on the interaction of neutral red with double-stranded DNA in large excess. Talanta 2001;55:321–8. 24. Marmur J. A procedure for the isolation of deoxyribonucleic acid from microorganisms. J Mol Biol 1961;3:208–18. 25. Zhou MF, He QZ. Synthesis, characterization, and biological properties of nano-rare earth complexes with L-glutamic acid and imidazole. J Rare Earth 2008;26:473–7. 26. Song YM, Xu JP, Ding L, Hou Q, Liu JW, Zhu ZL. Syntheses, characterization and biological activities of rare earth metal complexes with curcumin and 1,10-phenanthroline-5,6-dione. J Inorg Biochem 2009;103:396–400. 27. Toylar MD, Carter CD, Wynter CI. The infra-red spectra and structure of the rare-earth benzoates. J Inorg Nucl Chem 1968;30:1503–11. 28. Gear WJ. The use of conductivity measurements in organic solvents for the characterization of coordination compounds. Coordin Chem Rev 1971;7:81–122. 29. He QZ, Wang ZM. Synthesis and characterization of the solid ternary complexes rare earths with L-proline and 1,10-phenanthroline. Chin J Inorg Chem 1999;15:721–6. 30. Yang YH, Li Y, Niu SY, Jin J, Chi YX. Preparation and fluorescence of lanthanide(III) coordination polymers (Ln:Eu, Sm, Tb, Gd). Chin J Appl Chem 2010;27:1055–60. 3 31. Wu HX, Xin CY. Syntheses and photoluminescence properties of Dy + -acetylacetone-1,10-phenanthroline ternary complexes doped with rare earth ions. Chin J Lumin 2006;27:270–4. 32. Yan B, Zhang HJ, Wang SB, Ni JZ. Synthesis, characterization, and photophysical properties of rare earth complexes of N-phenyl-2aminobenzoic acid and 1,10-phenanthroline. Monatsh Chem 1998;129:567–75. 33. Nafisi S, Saboury AA, Keramat N, Neault JF, Tajmir-Riahi HA. Stability and structural features of DNA intercalation with ethidium bromide, acridine orange and methylene blue. J Mol Struct 2007;827:35–43.
Copyright © 2014 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence
H.-J. Sun et al. 34. Zhang GW, Guo JB, Pan JH, Chen XX, Wang JJ. Spectroscopic studies on the interaction of morin-Eu(III) complex with calf thymus DNA. J Mol Struct 2009;923:114–9. 35. Rehman JP, Barton JK. H NMR Studies of Tris(phenanthroline) metal complexes bound to oligonucleotides: characterization of binding modes. Biochemistry 1990;29:1701–10. 36. Lakowicz JR, Webber G. Quenching of fluorescence by oxygen: a probe for structural fluctuations in macromolecules. Biochemistry 1973;12:4171–9. 37. Barton JK, Goldberg JM, Kumar CV, Turro NJ. Binding modes and base specificity of tris (phenanthroline) ruthenium (П) enantiomers with nucleic acids: tuning the stereoselectivity. J Am Chem Soc 1986;108:2081–8. 38. Pyle AM, Rebmann JP, Meshoyer R, Lumar CV, Tuto NJ, Barton JK. Mixed-ligand complexes of ruthenium(II): factors governing binding to DNA. J Am Chem Soc 1989;111:3051–8. 39. Tysoe SA, Morgan RJ, Baker AD, Strekas TC. Spectroscopic investigation of differential binding modes of delta- and lambda-Ru(bpy)2ppz (2+) with calf thymus DNA. J Phys Chem 1993;97:1707–11.
wileyonlinelibrary.com/journal/luminescence
40. Yue B, Sun HJ, Chen YN, Kong K, Chu HB, Zhao YL. DNA binding and antibacterial properties of ternary lanthanide complexes with salicylic acid and phenanthroline. Appl Organomet Chem 2013;28:162–8. 41. Mitsopoulou CA, Dagas CE, Makedonas C. Characterization and DNA interaction of the Pt(II)(pq)(bdt)complex: A theoretical and experimental research. Inorg Chim Acta 2008;361:1973–82. 42. Bhat IH, Tabassum S. Synthesis of new piperazine derived Cu(II)/Zn (II) metal complexes, their DNA binding studies, electrochemistry and anti-microbial activity: Validation for specific recognition of Zn (II) complex to DNA helix by interaction with thymine base. Spectrochim Acta A 2009;72:1026–33. 43. Priya S, Balakrishna MS, Mague JT, Mobin SM. Insertion of carbon fragments into P(III) N bonds in aminophosphines and aminobis (phosphines): synthesis, reactivity, and coordination chemistry of resulting phosphine oxide derivatives. Crystal and molecular n n n structures of (Ph2P(O)CH2)2NR (R = Me, Pr, Bu), Ph2P(O)CH(OH) Pr, and cis-(MoO2Cl2{(Ph2P(O)CH2)2NEt-κ O, κO}). Inorg Chem 2003;42:1272–81.
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Revised: 31 March 2014,
Accepted: 05 April 2014
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.2701
Fluorescent studies on the interaction of DNA and ternary lanthanide complexes with cinnamic acid-phenanthroline and antibacterial activities testing Hui-Juan Sun,† Ai-Ling Wang,† Hai-Bin Chu* and Yong-Liang Zhao* ABSTRACT: Twelve lanthanide complexes with cinnamate (cin–) and 1,10-phenanthroline (phen) were synthesized and characterized. Their compositions were assumed to be RE(cin)3phen (RE3+ = La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Tm3+, Yb3+, Lu3+). The interaction mode between the complexes and DNA was investigated by fluorescence quenching experiment. The results indicated the complexes could bind to DNA and the main binding mode is intercalative binding. The fluorescence quenching constants of the complexes increased from La(cin)3phen to Lu(cin)3phen. Additionally, the antibacterial activity testing showed that the complexes exhibited excellent antibacterial ability against Escherichia coli, and the changes of antibacterial ability are in agreement with that of the fluorescence quenching constants. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: lanthanide complexes; cinnamic acid; 1,10-phenanthroline; DNA-binding; antibacterial activities
Introduction Recently, due to potential applications of metal complexes as anticancer drugs or as complexes with other biological functions, more attention has been paid for the interactions of metal complexes with nucleic acids (1). In addition, the interactions of the complexes with DNA depend on the mode and the affinity between the complexes and DNA (2–6). Generally, these interactions primarily involve three binding modes: intercalative, groove and electrostatic (7). The intercalative binding is stronger than other two binding modes because the surface of intercalative molecule is sandwiched between the aromatic heterocyclic base pairs of DNA (8,9). Cinnamic acid (Hcin) is a compound that can be found in plants, especially in flavorings and products containing cinnamon oil (10). Hcin and its derivates are described to possess a broad therapeutic action, including antimicrobial activity (11) and antifungal activity (12). Hcin has been widely used in medicines, pesticides, plastic, preservatives, food flavors, photosensitive resins, local anesthetics and fungicides (10,13–15). It exhibits superior antitumor activity against human malignant tumors, and can inhibit tumorous proliferation and induce its differentiation (16,17). Lanthanide complexes have shown unique biological activities (18,19). Polypyridine ligands (such as 2,2′-bipyridine, 1,10-phenanthroline [phen]) also have some antibacterial activities (20). Lanthanide complexes with two or more bioactive functional groups are likely to be anticarcinogens, which are less toxic, more efficient and more economical compared with the single functional group compounds. Synthesis and characterization of lanthanide complexes with cin– ions and phen as ligands have been studied (21), but there are few reports about their DNA-binding and antibacterial properties. Herein, 12 lanthanide complexes with cin– ion as anion ligand and phen as neutral ligand were synthesized and characterized. The properties of DNA binding with these
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complexes were studied using fluorescence spectroscopy with a view to evaluating their pharmaceutical activities. Antibacterial activities of the complexes also were investigated and the antimicrobial activities of the complexes are stronger than those of ligands and lanthanide ions, respectively.
Materials and methods Materials and general methods Calf thymus DNA (Sigma Chemical Co., St. Louis, MO, USA), tris (hydroxymethyl) aminomethane hydrochloride and ethidium bromide (EB) are used as received. Purities of rare earth oxides are 99.99%. Other reactants and solvents are all of analytical grade if not mentioned. Elemental analysis of C, H and N was performed with a Vario EL Cube elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). The molar concentration of rare earth was determined by EDTA titration method with xylenol orange as indicator in hexamethylenetetramine-HCl buffer solution. Molar conductivity was measured by DDSJ-308A conductivity meter at 25° C with N,N-dimethylformamide (DMF) as solvent and the concentration of complexes was 1.0 × 10–3 mol/L. Infrared spectra were recorded on a Nicolet Nexus 670 Fourier transform-infrared * Correspondence to: H.-B. Chu and Y.-L. Zhao, College of Chemistry and Chemical Engineering, Inner Mongolia University, Huhhot, 010021, China. E-mail: [email protected]; [email protected] †
These authors contributed equally to this work. College of Chemistry and Chemical Engineering, Inner Mongolia University, Huhhot, 010021, China
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H.-J. Sun et al. spectrometer (Nicolet Instrument Inc., Madison, WI, USA) using KBr pellet. The thermogravimetric (TG) analysis and differential scanning calorimetry were performed by a NETZSCHSTA 409 PC instrument (NETZSCH GmbH & Co., Selb, Germany) with a heating rate of 10 ºC/min under an air atmosphere. Absorption spectra were recorded on a Tu-1901 spectrophotometer (Beijing Purkinje General Instrument Co. Ltd., Beijing, China), by dissolving the complexes in DMF and diluted to 1.0 × 10–5 mol/L using absolute ethanol. Fluorescence quenching experiments were carried on the Shimadzu RF5301PC spectrophotometer (Shimadzu Corp., Kyoto, Japan) with excitation and emission slit width were 10.0 nm at room temperature.
Preparation of lanthanide complexes Preparation of rare earth chloride. Rare earth oxides were dissolved in a certain amount of hydrochloric acid. The mixture was heated until crystallized film appeared above the solution, after which the mixture was cooled to room temperature. A white powdered solid appeared. The powder was dissolved in anhydrous ethanol (22). Preparation of rare earth complexes. Phen 0.5 mmol was dissolved in anhydrous ethanol, and then an aqueous solution of 1.5 mmol sodium cinnamate (C6H5CH=CHCOONa) was added. A few minutes later, 0.5 mmol LaCl3 was added dropwise in to this mixture with continuous stirring under constant temperature of 60°C. The pH value of the solution was adjusted to 6.8 with NH3·H2O. After stirring at 60°C for 3 h, the solution was left still overnight at room temperature. The precipitate was separated by filtering and washing with anhydrous ethanol. Dried at 50°C for several hours, the complex La(cin)3phen was obtained. Other 11 complexes were prepared in a similar way.
solutions of the lanthanide complexes (1.0 × 10–3 mol/L) were prepared by dissolving the complexes in DMF and diluted to 1.0 × 10–5 mol/L by doubly distilled water. EB stock solution was prepared by dissolving its crystal in doubly distilled water according to CDNA/CEB = 20. Test of antibacterial activity In vitro antibacterial activity of the ligands and the complexes against Escherichia coli was studied by using the filter paper disc diffusion method (25,26). The E. coli was spread on sterile Luria-Bertani agar plates by using a sterile cotton swab. Six mm diameter sterile filter papers were taken and coated with 20 μL 0.004, 0.008 and 0.012 mol/L solution of Hcin, phen and the 12 complexes in DMF respectively, which were placed at the center of the lawn carefully without touching the other parts. Flat plates were incubated at 37°C for 16–18 h. Their inhibition diameters (including filter paper) were measured with a Vernier caliper. All experiments were carried out in parallel three times and the average diameter values were calculated.
Results and discussion Characterization of the complexes
Preparation of calf thymus DNA solution and ethidium bromide solution
Composition analysis and molar conductivity. The data of elemental analyses (C, H and N) and rare earth EDTA titration of the complexes are shown in Table 1. The results indicated that the composition of the complexes are RE(cin)3phen (RE3+=La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Tm3+, Yb3+, Lu3+). The molar conductance values of these complexes in DMF are in the range 14.1–28.9 S·cm2/mol. These small values indicated that only a small section of rare earth complexes ionize in DMF solution and these complexes are non-electrolytes (27,28).
The stock solution of calf thymus DNA was prepared by dissolving appropriate solid DNA into doubly distilled water and stored at 4°C. The concentration of DNA in stock solution was determined by ultraviolet (UV) absorption at 260 nm using a molar absorption coefficient ε260 = 6600 L/mol·per cm (23). The purity of the DNA was checked by monitoring the ratio of the absorbance at 260 nm to that at 280 nm. The solution gave a ratio of 1.8–2.0 at A260/A280, indicating that DNA was sufficiently free from protein (24). The stock
Thermogravimetric analysis–differential scanning calorimetry. The TG analysis and differential scanning calorimetry of some the complexes was studied and it was found that the thermal behaviors of the complexes are quite similar. During the heating of the complexes, the TG curves underwent a series of thermal changes associated with weight loss of the samples. As shown in Fig. 1, the Sm(cin)3phen complex begins to decompose at about 300ºC with obvious weight loss. The weight loss of the
Table 1. Composition analysis and molar conductivities (S·cm2/mol) of the lanthanide complexes Complexes La(cin)3phen Pr(cin)3phen Nd(cin)3phen Sm(cin)3phen Eu(cin)3phen Gd(cin)3phen Tb(cin)3phen Dy(cin)3phen Ho(cin)3phen Tm(cin)3phen Yb(cin)3phen Lu(cin)3phen
C% 61.16 (61.59) 61.09 (61.43) 60.61 (61.16) 60.52 (60.68) 60.02 (60.55) 59.86 (60.14) 59.68 (60.01) 59.27 (59.74) 59.12 (59.55) 58.82 (59.25) 59.06 (58.94) 58.34 (58.80)
H% 3.894 3.893 3.864 3.454 3.960 3.836 3.808 3.773 3.761 3.666 3.300 3.683
(3.84) (3.83) (3.82) (3.79) (3.78) (3.75) (3.74) (3.73) (3.72) (3.70) (3.68) (3.67)
N% 3.57 3.65 3.65 3.67 4.05 3.15 3.12 3.41 3.54 3.49 3.30 3.27
(3.68) (3.67) (3.66) (3.63) (3.62) (3.60) (3.59) (3.57) (3.56) (3.54) (3.52) (3.52)
RE % 18.31 18.46 18.90 19.59 19.58 20.56 20.63 21.01 20.96 21.78 22.03 22.27
(18.26) (18.48) (18.83) (19.48) (19.64) (20.19) (20.36) (20.72) (20.97) (21.37) (21.77) (21.96)
Λm 28.6 28.9 27.1 27.2 27.9 28.1 28.3 26.9 18.4 16.5 14.2 14.1
The values in brackets are theoretical values.
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Spectra on the interaction and antibacterial activities testing Ultraviolet-visible absorption spectra. The UV-visible absorption spectra of ligands phen, Hcin and all complexes were determined with a mixture solution (DMF–absolute ethanol = 1 : 5) as reference in the range 200–400 nm. As shown in Fig. 3, free ligands (Hcin and phen) and the complex Nd(cin)3phen show strong absorption. The band of Hcin shifted from 270 nm to 266 nm in the complex, which indicated that the rare earth ions coordinated with cin–. It also can be seen that the absorption band of phen at 264 nm shifted to 266 nm after being coordinated in the complexes, indicating that the ligand phen was involved in the coordination. Moreover, the λmax of the complex is near to that of phen, which may due to the π–π* transition energy of phen is much stronger than that of Hcin (32). Interactions of the complexes with DNA Figure 1. TG-DSC curves of Sm(cin)3phen. DSC, differential scanning calorimetry; TG, thermogravimetric.
complex about 308ºC is 23.64%, which could be assigned to the theoretical content of the complex containing one phen (23.34%). The weight loss of 56.96% at about 473ºC is consistent with the theoretical value of losing three cin– ions (57.18%). Of the initial mass of the sample 23.71% was left as a residue of 1/2Sm2O3 (calculated 22.58%). Infrared spectra. In the range 4000–400/cm, the infrared spectra of ligands phen, Hcin and all the complexes were determined, some of which are given in Fig. 2. The peaks at 1685/cm, 1283/cm and 1402/cm could be attributed to the ν(C=O) vibration, δO-H rocking vibration and ν(C-O) vibration of ligand Hcin, which disappeared after the formation of the complexes. Two new peaks emerged at 1406/cm and 1582/cm, which could be assigned to the symmetric and antisymmetric stretching vibrations of the carboxylate group, respectively. In addition, a new peak appeared in the region 482–485/cm could be attributed to the RE-O absorption peak. These changes indicated that the carboxyl coordinate with the rare earth ions in the complexes (29,30). After introducing the neutral ligands, the ν(C=N) of phen at 1587/cm shifted to near 1568/cm in the complexes, which revealed that the two nitrogen atoms of phen coordinated to the rare earth ions and formed a chelate ring (31).
Figure 2. Infrared spectra of ligands and some complexes: (a) Hcin; (b) phen; (c) La(cin)3phen; (d) Tb(cin)3phen; (e) Tm(cin)3phen.
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The fluorescence spectra of DNA-EB solution (1.0 mL 1.0 × 10–5 mol/L DNA and 1.0 mL 5.0 × 10–7 mol/L EB) were recorded with increasing amounts of rare earth complex (1.0 × 10–3 mol/L, 10 μL each time). The excitation wavelength was selected as 537 nm and the emission spectra were recorded from 570 nm to 630 nm. The DNA-EB system has a characteristic emission band around 592 nm. Fig. 4 showed the emission spectra of the DNA-EB system in the absence and presence of the Pr(cin) 3phen complex, when the solution of Pr(cin)3phen was added, the fluorescence intensity of the DNA-EB solution was gradually weakened with increasing amounts of the complex. Here EB has been employed in the examination of the reaction, as EB presumably binds initially to DNA by intercalation (33). It suggested that Pr(cin)3phen substituted for EB from the binding sites in the DNA-EB system, which led to a large decrease in the emission intensity of the DNA-EB system after adding the complex solution. Besides, the control experiment showed that the presence of lanthanide complexes would not decrease the fluorescence intensity of EB without DNA. Therefore, the results indicated that the complexes had a strong interaction with DNA, and the major binding mode was intercalative binding. This binding mode has been observed in some instances (34,35). The quenching plots illustrated that the quenching of EB bound to DNA by the complex is a good agreement with the linear Stern–Volmer equation (36):
Figure 3. Ultraviolet spectra of the ligands and complex: (a) Hcin; (b) phen; (c) Nd –5 (cin)3phen. The concentrations are all 1 × 10 mol/L.
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H.-J. Sun et al. the intercalative binding of the complexes to DNA bases (38–40). The changes in relative viscosity of DNA solution with increasing concentrations of Pr(cin)3phen were also observed. The value of relative viscosity enhanced with increasing the amounts of the complex further suggested that the interaction mode of the complexes with DNA should be intercalation binding (41,42).
Antibacterial activity of ligands and complexes
Figure 4. Effect of Pr(cin)3phen on the fluorescence spectra of ethidium bromide–DNA system. Arrow shows the intensity changes as increasing amounts of the complex. The inset is Stern–Volmer quenching curves.
F 0 =F ¼ 1 þ K q ½Q
Where F0 is the emission intensity in the absence of quencher (complex), F is the emission intensity in the presence of quencher, Kq is the quenching constant and [Q] is the concentration of the quencher. Plots of F0/F versus [Q] should appear to be linear. Taking Pr(cin)3phen as example, Kq is obtained from the slope of the F0/F versus (DNA) linear plot (inset of Fig. 4), and is found to be 3.13 × 104 mol/L, which indicate a strong interaction of lanthanide complex with DNA. The data of the fluorescence quenching constants were presented in Table 2. It can be seen when the lanthanide ion radius decreases, the corresponding ternary complex gets a higher fluorescence quenching constant. The data suggest that the binding ability of Lu(cin)3phen is the highest and La(cin)3phen is the lowest. The Lu3+ has the smallest ion radius, the biggest charge density and, thus, the strongest electrostatic interaction with DNA in these complexes. Consequently, the capacity of phen in Lu(cin)3phen inserting into the base pairs of DNA is the strongest and the fluorescence quenching constant is the biggest (37). On the contrary, the capacity of La(cin) 3phen inserting into the base pairs is the weakest and the fluorescence quenching constant is the smallest. To investigate further whether the interactions between DNA and lanthanide complexes involved intercalation, the interaction between the rare earth complexes and calf thymus DNA was investigated using UV-visible spectrophotometry and viscosity measurement. As the DNA concentration increased, the absorption spectra of Sm(cin)3phen, Gd(cin)3phen and Lu(cin)3phen showed clear hypochromicity at the maximum of 266 nm, together with a red shift of about 2.5 nm. The hypochromicity and red shift in the absorption spectra of the complexes proved
The antibacterial activity of the ligands and some complexes were evaluated by the flat-filter paper method against strains belonging to E. coli. Fig. 5 shows the antibacterial ring of the ligands and Lu (cin)3phen with different concentrations on E. coli. The concentrations of the complex and ligands are: (1) 0.004 mol/L Lu(cin)3phen; (2) 0.008 mol/L; Lu(cin)3phen; (3) 0.012 mol/L Lu(cin)3phen; (4) 0.012 mol/L phen; (5) 0.012 mol/L Hcin; and (6) DMF, respectively. The antibacterial activities of the complexes expressed as the diameter of growth inhibition area in millimeters are listed in Table 3. From Table 3 and Fig. 5, the following conclusions are obtained. First, all these complexes exhibited a stronger inhibitory effect on the E. coli than the ligands. Second, the antibacterial activities of the lanthanide complexes enhanced with the increasing concentration of the complexes. Third, the antimicrobial activities of higher molecular weight rare earth complexes are greater than the lower molecular weight rare earth complexes. The antibacterial mechanism is presumably that the complexes affect the functions associated with cell division of fungi such as cell wall, protein and/or DNA biosyntheses or kill the exponentially growing cells (26,43). Besides, as proven by the preliminary test (MTT method), some have the ability to kill leukemia cancer cells and cervical cancer cells.
Figure 5. Antibacterial ring of ligands and Lu(cin)3phen with different concentrations on E. coli.
Table 2. Fluorescence quenching constants of the complexes interaction with DNA Complexes
La(cin)3phen
Pr(cin)3phen
Nd(cin)3phen
Sm(cin)3phen
Eu(cin)3phen
Gd(cin)3phen
Kq (mol/L) Complexes Kq (mol/L)
2.50 × 104 Tb(cin)3phen 4.98 × 104
3.13 × 104 Dy(cin)3phen 5.12 × 104
3.90 × 104 Ho(cin)3phen 5.81 × 104
4.17 × 104 Tm(cin)3phen 6.49 × 104
4.41 × 104 Yb(cin)3phen 6.51 × 104
4.88 × 104 Lu(cin)3phen 7.12 × 104
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Spectra on the interaction and antibacterial activities testing Table 3. Inhibition zone diameter of the ligands and complexes/mm Concentration Compounds N,N-dimethylformamide Hcin Phen Pr(cin)3phen Sm(cin)3phen Eu(cin)3phen Gd(cin)3phen Dy(cin)3phen Lu(cin)3phen
0.004 mol/L
0.008 mol/L
0.012 mol/L
< 10 – < 10 13.9 15.8 16.5 16.5 18.5 18.9
< 10 – < 10 16.2 17.1 17.4 17.8 18.9 19.3
< 10 < 10 14 20.4 21.6 21.7 22.0 22.7 23.5
Conclusions In summary, 12 ternary lanthanide complexes with cin– as anion ligand and phen as neutral ligand have been prepared and characterized. To evaluate further their potential pharmaceutical activities, the DNA binding properties and antibacterial abilities were investigated by fluorescence quenching spectra and the flat-filter paper method. It was found that the 12 complexes could bind to DNA. The mainly interaction modes are found to be intercalative. The fluorescence quenching constants suggest that the binding ability of Lu(cin)3phen is the highest and La (cin)3phen is the lowest. According to the antibacterial testing results, all these complexes exhibit excellent antibacterial ability against E. coli and the complexes have stronger antibacterial abilities than each ligand and rare earth ions. These complexes may find applications in antibacterial agents, antitumor drugs and other related fields. Acknowledgments The research work is supported by the National Natural Science Foundation of China (21161013), Natural Science Foundation of Inner Mongolia (2011MS0202) and the Opening Foundation for Significant Fundamental Research of Inner Mongolia (2010KF03).
References 1. Rauf S, Gooding JJ, Akhtar K, Ghauri MA, Rahman M, Anwar MA, et al. Electrochemical approach of anticancer drugs-DNA interaction. J Pharm Biomed Anal 2005;37:205–17. 2. Nagane R, Koshigoe T, Chikira M. Interaction of Cu (II)-Arg-Gly-His-Xaa metallopeptides with DNA: effect of C-terminal residues, Leu and Glu. J Inorg Biochem 2003;93:204–12. 3. Zeng YB, Yang N, Liu WS, Tang N. Synthesis, characterization and DNA-binding properties of La(III) complex of chrysin. J Inorg Biochem 2003;97:258–64. 4. Silvestri A, Barone G, Ruisi G, Lo Giudice MT, Tumminello S. The interaction of native DNA with iron(III)-N,N′-ethylene-bis(salicylideneiminato)chloride. J Inorg Biochem 2004;98:589–94. 5. Mansouri-Torshizi H, I-Moghaddam M, Divsalar A, Saboury AA. 2,2′Bipyridinebutyldithiocarbamatoplatinum(II) and palladium(II) complexes: synthesis, characterization, cytotoxicity, and rich DNA-binding studies. Bioorgan Med Chem 2008;16:9616–25. 6. Sahoo BK, Ghosh KS, Bera R, Dasgupta S. Studies on the Interaction of diacetylcurcumin with calf thymus-DNA. Chem Phys 2008;351:163–9. 7. Tjahjono DH, Akutsu T, Yoshioka N, Inoue H. Cationic porphyrins bearing diazolium rings: synthesis and their interaction with calf thymus DNA. Biochim Biophys Acta 1999;1472:333–43.
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8. Ling LS, He ZK, Chen F, Zeng YE. Single-mismatch detection using nucleic acid molecular “light switch”. Talanta 2003;59:269–75. 9. He XQ, Lin QY, Hu RD, Lu XH. Synthesis, characterization and DNAbinding studies on La(III) and Ce(III) complexes containing ligand of N-phenyl-2-pyridinecarboxamide. Spectrochim Acta A 2007;68:184–90. 10. Hoskins JA. The occurrence, metabolism and toxicity of cinnamic acid and related compounds. J Appl Toxicol 1984;4:283–92. 11. Ramanan PN, Rao MN. Antimicrobial activity of cinnamic acid derivates. Ind J Exp Biol 1987;25:42–3. 12. Tawata S, Taira S, Kobamoto N, Zhu J, Ishihara M, Toyama S. Synthesis and antifungal activity of cinnamic acid esters. Biosci Biotechnol Biochem 1996;60:909–10. 13. Marques LF, Junior AABC, Correa CC, Lahoud MG, Silva RRD, Ribeiro SJL, et al. First crystal structures of lanthanide-hydrocinnamate complexes: Hydrothermal synthesis and photophysical studies. J Photochem Photobiol A 2013;252:69–76. 14. Raskin I. Role of salicylic acid in plants. Annu Rev Plant Physiol Plant Mol Biol 1992;43:439–63. 15. Liu L, Hudgins WR, Shack S, Yin MQ, Samid D. Cinnamic acid: a natural product with potential use in cancer intervention. Int J Cancer 1995;62:345–50. 16. Opdyke DLJ. Monographs on fragrance raw materials. Food Cosmet Toxicol 1975;13:687–90. 17. Yen GC, Chen YL, Sun FM, Chiang YL, Lu SH, Weng CJ. Accomparative study on the effectiveness of cis- and trans- form of cinnamic acid treatments for inhibiting invasive activity of human lung adenocarcinoma cells. Eur J Pharm Sci 2011;44:281–7. 18. Zhang YH. Cinnamic acid and its derivatives with tumor. Cancer Res Clin 2001;13:353–5. 19. Wang Q, Yang Z, Qi GF, Qin DD. Synthesis, crystal structure, antioxidant activities and DNA-binding studies of the Ln (Ш) complexes with 7-methoxychromone-3-carbaldehyde-(4′-hydroxy) benzoyl hydrazine. Eur J Med Chem 2009;44:2425–33. 20. Khan IM, Ahmad A, Aatif M. Synthesis, single-crystal characterization, antimicrobial activity and remarkable in vitro DNA interaction of hydrogen-bonded proton-transfer complex of 1,10-phenanthroline with 2,4,6-trinitrophenol. J Photochem Photobiol B 2011;105:6–13. 21. Zhao YL, Lian XS, Wu YM. Synthesis of ternary solid complexes of cinnamic acid-o-phenanthroline. Acta Sci Nat Univ NeiMenggu 1993;24:553–4. 22. Huang CH. Coordination Chemistry of Rare Earth. Science Press, Beijing, 1997. 23. Huang CZ, Li YF, Feng P. A spectrophotometric study on the interaction of neutral red with double-stranded DNA in large excess. Talanta 2001;55:321–8. 24. Marmur J. A procedure for the isolation of deoxyribonucleic acid from microorganisms. J Mol Biol 1961;3:208–18. 25. Zhou MF, He QZ. Synthesis, characterization, and biological properties of nano-rare earth complexes with L-glutamic acid and imidazole. J Rare Earth 2008;26:473–7. 26. Song YM, Xu JP, Ding L, Hou Q, Liu JW, Zhu ZL. Syntheses, characterization and biological activities of rare earth metal complexes with curcumin and 1,10-phenanthroline-5,6-dione. J Inorg Biochem 2009;103:396–400. 27. Toylar MD, Carter CD, Wynter CI. The infra-red spectra and structure of the rare-earth benzoates. J Inorg Nucl Chem 1968;30:1503–11. 28. Gear WJ. The use of conductivity measurements in organic solvents for the characterization of coordination compounds. Coordin Chem Rev 1971;7:81–122. 29. He QZ, Wang ZM. Synthesis and characterization of the solid ternary complexes rare earths with L-proline and 1,10-phenanthroline. Chin J Inorg Chem 1999;15:721–6. 30. Yang YH, Li Y, Niu SY, Jin J, Chi YX. Preparation and fluorescence of lanthanide(III) coordination polymers (Ln:Eu, Sm, Tb, Gd). Chin J Appl Chem 2010;27:1055–60. 3 31. Wu HX, Xin CY. Syntheses and photoluminescence properties of Dy + -acetylacetone-1,10-phenanthroline ternary complexes doped with rare earth ions. Chin J Lumin 2006;27:270–4. 32. Yan B, Zhang HJ, Wang SB, Ni JZ. Synthesis, characterization, and photophysical properties of rare earth complexes of N-phenyl-2aminobenzoic acid and 1,10-phenanthroline. Monatsh Chem 1998;129:567–75. 33. Nafisi S, Saboury AA, Keramat N, Neault JF, Tajmir-Riahi HA. Stability and structural features of DNA intercalation with ethidium bromide, acridine orange and methylene blue. J Mol Struct 2007;827:35–43.
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wileyonlinelibrary.com/journal/luminescence
H.-J. Sun et al. 34. Zhang GW, Guo JB, Pan JH, Chen XX, Wang JJ. Spectroscopic studies on the interaction of morin-Eu(III) complex with calf thymus DNA. J Mol Struct 2009;923:114–9. 35. Rehman JP, Barton JK. H NMR Studies of Tris(phenanthroline) metal complexes bound to oligonucleotides: characterization of binding modes. Biochemistry 1990;29:1701–10. 36. Lakowicz JR, Webber G. Quenching of fluorescence by oxygen: a probe for structural fluctuations in macromolecules. Biochemistry 1973;12:4171–9. 37. Barton JK, Goldberg JM, Kumar CV, Turro NJ. Binding modes and base specificity of tris (phenanthroline) ruthenium (П) enantiomers with nucleic acids: tuning the stereoselectivity. J Am Chem Soc 1986;108:2081–8. 38. Pyle AM, Rebmann JP, Meshoyer R, Lumar CV, Tuto NJ, Barton JK. Mixed-ligand complexes of ruthenium(II): factors governing binding to DNA. J Am Chem Soc 1989;111:3051–8. 39. Tysoe SA, Morgan RJ, Baker AD, Strekas TC. Spectroscopic investigation of differential binding modes of delta- and lambda-Ru(bpy)2ppz (2+) with calf thymus DNA. J Phys Chem 1993;97:1707–11.
wileyonlinelibrary.com/journal/luminescence
40. Yue B, Sun HJ, Chen YN, Kong K, Chu HB, Zhao YL. DNA binding and antibacterial properties of ternary lanthanide complexes with salicylic acid and phenanthroline. Appl Organomet Chem 2013;28:162–8. 41. Mitsopoulou CA, Dagas CE, Makedonas C. Characterization and DNA interaction of the Pt(II)(pq)(bdt)complex: A theoretical and experimental research. Inorg Chim Acta 2008;361:1973–82. 42. Bhat IH, Tabassum S. Synthesis of new piperazine derived Cu(II)/Zn (II) metal complexes, their DNA binding studies, electrochemistry and anti-microbial activity: Validation for specific recognition of Zn (II) complex to DNA helix by interaction with thymine base. Spectrochim Acta A 2009;72:1026–33. 43. Priya S, Balakrishna MS, Mague JT, Mobin SM. Insertion of carbon fragments into P(III) N bonds in aminophosphines and aminobis (phosphines): synthesis, reactivity, and coordination chemistry of resulting phosphine oxide derivatives. Crystal and molecular n n n structures of (Ph2P(O)CH2)2NR (R = Me, Pr, Bu), Ph2P(O)CH(OH) Pr, and cis-(MoO2Cl2{(Ph2P(O)CH2)2NEt-κ O, κO}). Inorg Chem 2003;42:1272–81.
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