Antituberculosis and cytotoxic activities of triorganotin(IV) complexes

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Chinese Chemical Letters 23 (2012) 731–735 www.elsevier.com/locate/cclet

Antituberculosis and cytotoxic activities of triorganotin(IV) complexes Hidayat Hussain a,b,*, Nazia Bibi c,d, Ahmed Al-Harrasi b, Salman Siddiqi e, Shahana U. Kazmi c, Ying Zhang d, Amin Badshah f a Department of Chemistry, University of Paderborn, 33098 Paderborn, Germany Department of Biological Sciences and Chemistry, College of Arts and Sciences, University of Nizwa, Oman c Immunology and Infectious Disease Research Laboratory, Department of Microbiology, University of Karachi, Pakistan d Department of Molecular Microbiology and Immunology Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA e Becton Dickinson Diagnostic Systems, Sparks, MD 21152, USA f Department of Chemistry, Quaid-e-Azam University, Islamabad, 45320, Pakistan b

Received 9 November 2011

Abstract Five triorganotin(IV) (1–5) complexes of cinnamic acid, (Z)-2-acetamido-3-phenylacrylic acid, 3-methylbut-2-enoic acid, and 2,2-diphenylacetic acid have been synthesized and characterized by 1H–13C–119Sn NMR, UV, and IR. The spectroscopic investigation demonstrated that the carboxylate group acts as a monodentate ligand in triorganotin(IV) compounds. Five triorganotin(IV) complexes were screened against the log phase culture of Mycobacterium tuberculosis H37Rv by colorimetric method using XTT dye as growth indicator. The MICs were found to be 0.08 and 1.25 mg/mL. # 2012 Hidayat Hussain. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Triorganotin(IV) complexes; Antituberculosis activity; MICs; Cytotoxicity

Tuberculosis (TB) is the leading cause of death worldwide and Pakistan ranks 8th among the 22 countries of high burden of TB with 297,108 new cases and an incidence of 181 cases/100, 000/year [1]. Antituberculosis drug resistance especially multidrug resistance (MDR-TB) and now extensively drug resistance (XDR-TB) are a big threat to tuberculosis control [2]. Therefore, there is a need to develop new, better and safe anti-TB drugs that can be used for the treatment of drug resistant tuberculosis [5]. Organotin compounds have recently been introduced having broad spectrum of activities including antibacterial, antifungal and antiviral and especially anticancer activities [3]. Present study was conducted to investigate the antituberculosis activities of triorganotin(IV) complexes. 1. Experimental Cinnamic acid, (Z)-2-acetamido-3-phenylacrylic acid, 3-methylbut-2-enoic acid, and 2,2-diphenylacetic acid, triphenyltin chloride and diphenyltin dichloride were commercially available. Other experimental (Instrumentation) are same as described in Ref. [4a]. * Corresponding author at: Department of Chemistry, University of Paderborn, 33098 Paderborn, Germany. E-mail address: [email protected] (H. Hussain). 1001-8417/$ – see front matter # 2012 Hidayat Hussain. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2012.03.011

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H. Hussain et al. / Chinese Chemical Letters 23 (2012) 731–735

1.1. The general method for the synthesis of triorganotin(IV) derivatives Five new triorganotin(IV) compounds (1–5) were prepared as follows: to a solution of the carboxylate ligands (cinnamic acid, (Z)-2-acetamido-3-phenylacrylic acid, 3-methylbut-2-enoic acid, and 2,2-diphenylacetic acid) (0.01 mol) in chloroform (50 mL) was added dry Et3N (0.1 mol) followed by the addition of the triorganotin chloride (0.01 mol) in solid form at 25 8C and the resulting mixture was heated under reflux for 3 h. After cooling the reaction mixture to 25 8C the precipitated Et3NHCl was filtered off and the solvent was removed from the filtrate by a rotary evaporation. The solid residue was triturated with ethanol to afford the pure products 1–5. 2. Results and discussion Five triorganotin(IV) 1–5 (Scheme 1; Fig. 1) were subsequently prepared by reactions of ligands (HL) such as cinnamic acid, (Z)-2-acetamido-3-phenylacrylic acid, 3-methylbut-2-enoic acid, and 2,2-diphenylacetic acid with triphenyltin chloride and diphenyltin dichloride (Scheme 1) in 2:1 (ligand:metal) molar ratio. 2.1. Mass spectrometry The molecular ion peak in almost all of derivatives was not observed. In the triorganotin (IV) derivatives 1–5 the major fragmentation observed is due to loss of the ligand moiety from the tin derivatives (Scheme 1; see Section 1) [4]. Successive fragmentation is observed by the loss of ‘‘R’’ groups (Me, Bu, Ph) until the Sn+ ion is obtained. In the alternative route ‘‘R’’ groups are eliminated first and in the next step a molecule of CO2 is evolved from the ligand moiety attached to the tin atom. In the successive steps the remaining substituents are lost from the tin atom. 2.2. 1H and

13

C NMR spectroscopy

Chemical shifts for the various protons in the compounds are given in Section 1. The conclusions drawn from the 1H NMR spectral studies lend further support to the mode of bonding discussed above. For instance, absence of signals between 10.00 and 13.00 ppm due to COOH protons confirms the deprotonation of the carboxylic acid oxygen atom of the ligand upon complexation [4a]. Most interestingly the geometry of the double bond in the maleate side chain was trans and not cis which would have been expected. Same results were supported by 13C NMR spectra (see Supporting information).

(C6H5)3SnCl + 3LHEt 3N

C6H5SnL3 + 3Et 3N.HCl

[R3Sn]+

(1)

-O2CR'

[R3SnO2CR']+-R [R2SnO2CR']+ -CO2

-R HL = cinnamic acid, (Z)-2-acetamido-3-phenylacrylic acid, 3-methylbut-2-enoic acid, and 2,2-diphenylacetic acid (C6H5)2SnCl2 + 3LHEt3N

[R2SnR']+

+

[R2Sn]

-R

-R

C6H5SnL2Cl + 3Et 3N.HCl (2)

[RSn]+

HL = cinnamic acid

[RSnR']+

[Sn]+

-RR' (a) General mass fragmentation pattern

(a) General synthetic scheme

Scheme 1. (a) General synthetic scheme for 1–5; (b) general mass fragmentation pattern for triorganotin(IV) carboxylates 1–5.

O 3 1 4

Ph

7

2

9

8

O

Sn

6

1 R = Ph 5 R = Cl

Ph O

Ph 2

Sn

O

3

1

Ph

O

Ph

2

Ph 3

HN

5

Ph =

O R

4

5

O

Sn

Ph

7

8

O

3 4

4' 1' 6'

Ph

O

1

5 6

3'

2'

2

4

Ph

5'

Fig. 1. Structures of triorganotin(IV) compounds 1–5.

Sn

Ph Ph

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2.3. Electronic spectra It was found that the electronic spectra of these complexes exhibit very intense bands in the range of 200–210 nm, which may be due to the n ! p* transition of the (COO) chromophore [4]. Furthermore, there is a sharp band observed in the 255–270 nm regions in the spectra of the complexes, which is ascribed to the charge-transfer band since it is known that metal/metalloids are capable of forming dp–pp bands with ligands containing nitrogen or oxygen as donor atoms [4]. 2.4. Infrared spectroscopy The IR spectra of these compounds have been recorded in the range of 400–4000 cm1. Tentative assignments have been made on the basis of earlier publications and the important data are mentioned in Section 1. The absorptions of interest in the spectra of the complexes are n(COO), n(Sn–C) and n(Sn–O). The absence of the n(OH) in all the organotin (IV) compounds in the 2500–3000 cm1 region, and the presence of n(Sn–O) in the 450–475 cm1 range [4] indicates deprotonation of the carboxylic acid group and consequent coordination of the carboxylate group with the tin metal as expected. The IR stretching frequencies of the carboxylate groups are very important for determining their structures viz., when there are interactions between the carbonyl oxygen atoms of the carboxylate groups and the tin atom, the asymmetric absorption vibration frequencies nasym(CO2) of the carboxylate groups decrease and the symmetric absorption frequencies nsym(CO2) increase. Their difference viz., nD(CO2), therefore decreases [4]. In the IR spectra of the title compounds the carboxylate bands are observed in the characteristic regions for nasym(CO2) between 1640 and 1575 cm1 and for nsym(CO2) between 1420 and 1310 cm1 (see Supporting information). 2.5.

119

Sn NMR spectra

119

Sn NMR chemical shifts of organotin(IV) compounds cover a range of roughly 600 ppm. These results are in agreement with the hypothesis of an increase in the coordination number of the tin atom in the complexes, and hence, of tin nuclear shielding [5]. 2.6. Antituberculosis activity Five organotin complexes 1–5 (Fig. 1) were screened for their antituberculosis activity against the logarithmic phase culture of M. tuberculosis H37Rv by rapid colorimetric XXT method. The compounds were found to be active at 10 mg/mL. Minimum inhibitory concentrations (MICs) were determined by broth microdilution method and were found to be in the range of 0.078–1.25 mg/mL. Compounds 1–4 showed activity at concentration 0.078 mg/mL whereas compound 5 exhibited activity at 1.25 mg/mL (Table 1). 2.7. Effect on cell viability Compounds 1 and 5 were tested for their inhibition of cellular viability and proliferation using human breast cancer MCF7 cell line by MTT-microculture tetrazolium assay. Compound 1 showed inhibition (above 90%) of cell viability at all concentrations tested (Fig. 2). Compound 5 showed inhibition of cell viability in a concentration dependent manner where least cytotoxicity (23%) was observed at 0.001 mg/mL whereas inhibition at concentrations of 0.01 and 0.1 mg/mL was found to be 88 and 93%, respectively (Fig. 2). Table 1 Antituberculosis activities of triorganotin(IV) complexes 1–5. Compounds

MICs (mg/mL)

Compounds

MICs (mg/mL)

1 2 3 4

0.078 0.078 0.078 0.078

5 Isoniazid Rifampin

1.25 0.1 0.2

Fig. 2. Inhibition of cell viability by compounds 1 and 5. Human breast cancer cells (MCF7) were treated at 1, 10 and 100 mg/mL of the compounds for 3 days following incubation with MTT for 4 h. Absorbance (550 nm) was read in a bioassay reader. Values represent percent inhibition of cell viability.

3. Conclusion Organotin compounds particularly triorganotins are known for their toxicity against variety of microorganisms. In this study all compounds 1–5 showed promising antituberculosis activity at concentration range of 0.078– 1.25 mg/mL. We found that compounds 1–4 possessing the same triphenyl group have superior antituberculosis activity then compound 5 possessing 2 phenyl groups which may be due to the fact that generally toxicity of the organotin compounds is associated with the organic ligand and the toxicity decreases with the order of tri > di > mono organotins [3b,6]. Mycobacterium tuberculosis is hard to treat organism being equipped with lipid and waxed cell envelop. The outer most structure is the cell wall which is composed of peptidoglycan– arabinogalactan backbone. Attached to this backbone structure are lipids and carbohydrate molecules which make the cell envelop highly complex and diverse in nature. This unique architecture of M. tuberculosis cell wall renders most of the antibiotics unable to penetrate [7]. Unlike various conventional antimicrobial compounds, organotin compounds because of their lipophilic properties have the ability to penetrate and accumulate in the lipid bilayers. Thus they can be a potential source of developing new class of quite promising antimycobacterial agents. Previous studies by Demertzi et al. have also revealed promising antituberculosis activities of organotin mefanamic complexes and organotin complexes of the non steroidal non inflammatory drugs (NSAIDs) of carboxylic acid family [8]. Organotin compounds exert their antimicrobial activity mainly by interfering with the membrane function including effect on energy transduction, in and out transportation of the solute molecules [9]. Furthermore, these compounds get solubilized in phospholipid bilayers and hence they change the physiological composition of the lipids. In this study we tested compounds 1 as a representative of compounds 1–4 which bear the same triorganotin pharmacophore and compound 5 having different pharmacophore and a Cl polar group attached. The results are in agreement with the reports suggesting that the toxicity of organotins is greatly influenced by the nature of the compounds in the order of tri to mono organotins [6]. In conclusion, the bioactivity of the organotin compounds shown in this study indicates potential development of new anti-tuberculosis drugs. Toxicity of these compounds is a concern. Studies are planned to further investigate the efficacy of these compounds in vitro as well as in vivo in animal models. Acknowledgments This study was partially supported by IRSIP-HEC fellowship to NB. SS is highly acknowledged for facilitating this study by providing lab supplies.

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Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.cclet.2012.03.011. References [1] (a) Global Tuberculosis Control: Epidemiology, Strategy, Financing, WHO report 2009, Geneva, World Health Organization, 2009 (WHO/ HTM/TB/2009.411). (b) C. Dye, S. Scheele, P. Dolin, et al. J. Am. Med. Assoc. 282 (1999) 677. [2] (a) R. Long, J. Can. Med. Assoc. 163 (2000) 425; (b) R.C. Goldman, K.V. Plumley, B.E. Laughon, Drug Targets 7 (2007) 73. [3] (a) K. Duncan, Tuberculosis 83 (2003) 201; (b) M. Gielen, Appl. Organomet. Chem. 16 (2002) 481; (c) V. Narayanan, M. Nasr, K.D. Paull, in: M. Gielen (Ed.), Tin-Based Anti-Tumor Drugs, Springer, Berlin, 1990, p. 201; (d) D. de Vos, R. Willem, M. Gielen, et al. Met. Based Drugs 5 (1998) 179. [4] (a) H. Hussain, V.U. Ahmad, I.R. Green, et al. ARKIVOC (2007) 145; (b) F. Ahmad, M. Pervez, S. Ali, et al. Synth. React. Inorg. Met. Org. Chem. 32 (2002) 665. [5] (a) J. Li, G. Zhao, G. Xiong, Y. Ma, Synth. React. Inorg. Met. Org. Chem. 31 (2001) 85; (b) D.A. Scudiero, R.H. Shoemaker, K.D. Paull, et al. Cancer Res. 48 (1988) 4827; (c) M. Nath, S. Pokharia, G. Eng, X. Song, J. Organomet. Chem. 669 (2003) 109; (d) G. Eng, X. Song, Q. Duong, et al. Appl. Organomet. Chem. 17 (2003) 218. [6] S. Tushar, B. Baul, Appl. Organomet. Chem. 22 (2008) 195. [7] (a) P.J. Brennan, Tuberculosis 83 (2003) 91; (b) V. Briken, S.A. Porcelli, G.S. Besra, L. Kremer, Mol. Microbiol. 53 (2004) 391. [8] (a) J.J. Cooney, S. Wuertz, J. Ind. Microbiol. 4 (1989) 375; (b) D.K. Demertzi, V. Dokorou, Z. Ciunik, et al. Appl. Organomet. Chem. 16 (2002) 360. [9] D.K. Demertzi, J. Organomet. Chem. 691 (2006) 1767.