Synthesis, Medicinal Applications and QSAR Study of Benzimidazole,Thiophene, Piperazine derivatives for Antimycobacterial, Antibacterial, Antifungal Activities

 

Kale Sachin. C¹, Upadhayay Ashutosh¹, Kale M. K²

¹M.J.R.P. University, Jaipur, Rajasthan, India.

²K.G.R.D. College of Pharmacy and Research Institute, Karjat, Raigad. Maharashtra, India.

 

ABSTRACT:

Benzimidazole,Thiophene,Piperazine derivatives regarded as an important heterocyclic motif that exhibits a wide range of Medicinal applications including Antimycobaterial,antibacterial, Antifungal, Anti- HIV’s. In the view of their wide ranging activities the synthesis of benzimidazole, Thiophene, Piperazine and its derivatives remain a primary focus for synthetic chemistry Communities. The association of HIV and TB infection is a serious problem. TB is caused by bacilli belonging to the Mycobacterium tuberculosis. In the Review of Literature it was observed that various method’s are available for synthesis of Benzimidazole, Thiophene,piperazine derivatives. Thirty seven compounds were synthesized and the structures of these compounds were established by means of IR, 1H-NMR, C¹³ NMR and elemental analysis. All compounds were evaluated for antibacterial, antifungal and antitubercular activities. Most of the compounds have shown significant antibacterial, antifungal and antitubercular activity when compared with the standard drug. QSAR Study will be done as per the need of Compound.

 

 

 

INTRODUCTION:

The increasing global tuberculosis burden due to the curse of  HIV, MDR and XDR-TB has lead to search of newer therapeutic agents to tackle the menance.  

 

The present first line drugs like INH, pyrazinamide, ethambutol, and rifampicin are potent antitubercular agent. They act by inhibition of mycolic acid and RNA / DNA synthesis. They possess numerous adverse reactions. To avoid these effects it seemed promising to look for more selective compounds, at other targets to suppress the activity ^1-3.

 

 

The Disease: Tuberculosis:

Tuberculosis (TB) is a potentially fatal contagious disease that can affect almost any part of the body but is mainly an infection of the lungs. It is caused by a bacterial microorganism, the tubercle bacillus or Mycobacterium tuberculosis. Although TB can be treated, cured, and can be prevented if persons at risk take certain drugs, scientists have never come close to wiping it out. Few diseases have caused so much distressing illness for centuries and claimed so many lives. 

 

Epidemiology:

Bacillus characteristics:

TB is caused by bacilli belonging to the Mycobacterium tuberculosis. In the majority of cases, TB is due to Mycobacterium tuberculosis (Koch's bacillus). M. africanum  may be observed in western Africa.

 

Medicinal Applications of Benzimidazole:

Benzimidazoles are regarded as a promising class of bioactive heterocyclic compounds that exhibit a range of biological activities. Specifically, this nucleus is a constituent of vitamin-B12. Several benzimidazoles are commercially available as pharmaceuticals. Benzimidazoles are the most widely studied drugs as anthelmintic. Recent studies have established that benzimidazole carbamates such as Albendazole, mebendazole, flubendazole, and fenbendazole  inhibit the in vitro growth of Trichomonas vaginalis and G. lamblia. Clinical reports have shown that albendazole is as effective as metronidazole,

 

Medicinal Application of Thiophene.:

Thiophene is a heterocyclic compound aromatic in nature consisting of four carbon atom and one sulfur atom in a five membered ring compound analogues to thiophene includes furan, and pyrrole. Where the sulfur is replaced by furan, and pyrrole. Where the sulfur is replaced by O and NH , respectively, Thiophene was discovered by viktor meyer in 1883. The benzene ring of a biologically active compound may often replaced by thiophene without loss of activity . This seen in example such as the NSAID loroxicam, the thiophene analog   piroxicam.

 

Medicinal Application of Piperazine.:

Piperazine  is  an  interesting  heterocyclic  moiety  as  constituent  of  several biologically active molecules.The polar nitrogen atoms in the piperazine ring confer bioactivity to molecules and enhance favorable interaction with macromolecules . Piperazinyl-linked ciprofloxacin dimers are potent antibacterial agents against resistant strains, antimalarial  agents  and  potential  antipsychotic  agents . Piperazine derivatives containing tetrazole nucleus have been reported as antifungal agents . Substituted benzamide piperazine derivatives have shown strong agonistic activity while the substituted acetamide piperazine derivative have better dopamine D4 receptor agonist activity as compared to substituted benzamide piperazine derivatives.

 

MATERIAL AND METHODS.:

Melting points were determined in open capillary method and are uncorrected. IR spectra were recorded on Thermo Nicolet IR 200 spectro-photometer using KBr disc method. The 1H-NMR spectra were recorded on sophisticated multinuclear FT-NMR Spectrometer model Avance-III (Bruker), using dimethylsulfoxide-d6 as solvent and tetramethylsilane as internal standard.

 

1) Method of Synthesis of Cinnamic Acid.:

By Doebner reaction:

Condensations of an aldehyde with malonic acid in pyridine solution, often in the    

  presence of a trace of piperidine.

 

 

 

2) Method of Syntheis of Benzimidazole.

Benzimidazoles are formed when o-phenylenediamine is heated with organic acid.

 

 

 

3) Method of Syntheis of Thiophene.:

Hinsberg’s Procedure:

A a-dicarbonyl compound is reacted with thioether in which the sulfur atom is adjacent to two activated methylene group.

 

 

 

4) Method of Synthesis of Piperazine.

 

 

A practical method allows the synthesis of alkyl-, alcohol-, amine-, and ester-extended tosylpiperazines under mild conditions with good yields. This protocol exhibits potential applicability in the synthesis of pharmaceuticals and natural products because of the operational simplicity and the conveniently available reactants.

 

Spectral Data of (BTPB1-BTPB5):

BTPB1:

IR(KBr) cm-1: 3005(Ar-Cl), 3223(-NH Str), 2919(-Ar-C-H Str ), 1672(C=0 Str), 1448 (C-N Str), 949(-Ar).461(CH2 def).1H NMR (CDCl3) : 4.29-4.42 (2H Methine), 3.44-3.83(6H of Methylene), 7.50-7.59 (4H of Benzimidazole), 7.27-7.40(5H of Benzene). C13 NMR: 129.1(C1 Aromatic), 134.7, (C4 Aromatic), 67.1(C5 of Methine), 36.1(C6 of Methine), 43.1(C7 Aliphatic), 207.1 (C8 of Carbonyl), 141.5(C9 of Benz), 123.4(C12 of Benz.), 43.9 (C13 Methylene), 61.9(C15 of Cyclohexane), 129.9 (C20 Aromatic ring). m.p. 180-182°C, yield 67%, mol. Wt. 544.45, C₂₉H₂₅N₄Cl O S (Found C: 63.90 H:4.52 N: 10.20 required C : 63.91 H: 4.59 N : 10.28).

BTPB2:

IR(KBr) cm-1: 3223 (-NH Str), 2919(Ar-C-H Str), 1672(-C=O Str), 1448(-C-N Str), 1005(-Ar), 461 CH2 def), 1H NMR (CDCl3): 4.29-4.40(2H of Methine), 2.86-3.83(6H of Methylene), 7.22-7.59(4H of Benzimidazole), 6.79-7.27(5H of Benzene). m.p. 276-277°C, yield 69%, mol. Wt. 510, C₂₉H₂₆N₄ O S. (Found C: 68.20 H:5.02 N:10.92 required C : 68.23 H: 5.09 N : 10.98 ).

 

BTPB3:

IR (KBr) cm-1: 3223(-NH Str), 2919(-Ar-C-H Str), 1530(N-O Str), 1672(-C=O Str), 1448(-C-N Str), 1340(-N-O Str), 749(-Ar), 461(CH2 def). 1H NMR (CDCl3): 4.29-4.42(2H of Methine), 2.97-3.83(6H of Methylene), 7.22-7.59 (4H of Benzimidazole), 7.02-8.08(4H of Benzene). m.p. 287-288°C, yield 69%, mol. Wt. 523., C₂₉H₂₅N₅O₃S (Found C: 66.50 H:4.75 N:11.42 required C: 66.53 H: 4.78 N: 11.47).

 

BTPB4:

IR (KBr)cm-1: 3223(-NHStr), 2919(-Ar-C-HStr), 1672(C=OStr), 1448(C-NStr), 980(-Ar), 461(CH2def) . 1H NMR (CDCl3): 4.29-4.42(2H of Methine), 2.97-3.83(6H of Methylene), 7.22-7.59 (4H of Benzimidazole), 7.02-8.08(4H of Benzene). m.p. 273-274°C, yield 71%, mol. Wt. 478. C₂₉H₂₆N₄ O S. (Found C: 72.75 H: 5.42 N: 11.69 required C: 72.80 H: 5.43 N: 11.71).

 

BTPB5:

IR(KBr) cm-1: 4352(-OH Str), 3207(NH Str), 2920(Tert. nitrogen), 1552(C-NO2 Str), 1433(-C-N Str), 1150(-C-F), 970(-Ar), 461(-CH2 def), 1H NMR: 4.29-4.42 (2H of Methine), 2.87-3.83 (6H of Methylene), 6.97-7.57(3H of Benzimidazole),6.54-7.27 (5H of Benzene). M.P.291-292°C, yield 73%, mol. Wt. 496. C₂₉H₂₅N₄ F O S (Found C: 70.10 H: 5.0 N: 11.21 required C: 70.16 H: 5.04 , N: 11.29).

 

Antimicrobial activity:

The antimicrobial activity of the synthesized compounds was determined by cup-plate method. The antibacterial activity was determined against gram-positive organism Staphylococcus aureus and gram-negative organism Escherichia coli at 50-mcg/ml and 75mcg/ml concentration of sample compounds. Dimethyl Formanide was used as control. The bacteria were subcultured on nutrient agar broth and incubated at 37⁰C for 18-24 hrs. Standard antibacterial drug Ciprofloxacin was also screened under similar conditions at 50-mcg/ml and 75mcg/ml concentration for comparison. The antifungal activity was carried out against the fungi Candida albicans and A. fumigatus at 50 mcg/ml and 75mcg/ml concentration of sample compounds. The fungi were subcultured in Sabourod’s dextrose agar medium. The fungal susceptibility testing was done by cup-plate method using Fluconazole (50 mcg/ml and 75mcg/ml concentration) as standard. The petri dishes were incubated a 37⁰C for18-24 hrs.

 

Antitubercular evaluation:

The antitubercular screening of synthesized compounds was carried out by middle brook 7H9 broth base (M198) medium against. H37Rv strain at100 mcg/ml, 125 mcg/ml and 250mcg/ml. L J Medium containing standard drug as well as control. Middle brook 7H9 broth base (M198) medium was inoculated with mycobacterium tuberculosis of H37Rv strain. The inoculated medium was incubated for 370 C for 6 weeks. At the end of 6 weeks the growth of mycobacterium tuberculosis was read. Streptomycin (100 mcg/ml, 125 mcg/ml and 250mcg/ml) was used as a standard drug.

QSAR Study:

Material Science study ,Bioluminate Compound structure study,Compound Stereo view with numbering and 3D Structure Scupling ,Ramchandran plot study will be done under QSAR Study.

 

 

 

 

 

Table No: 1   IUPAC names of the synthesized compounds. (BC)

Compounds	Structures	IUPAC Names
BC1
BC2
BC3
B­C4
BC5
BC6
BC7
BC8

 

Table No: 2 IUPAC names of the synthesized compounds. (BT)

BT1		2-(2-(3-(furan-2-yl)-4-oxotetrahydrothiophen-2-yl)-1H-benzo[d]imidazol-1-yl)acetic acid
BT2		2-(5-chloro-2-(3-(4-hydroxyphenyl)-4-oxotetrahydrothiophen-2-yl)-1H-benzo[d]imidazol-1-yl)acetic acid
BT3		2-(2-(3-(4-methoxyphenyl)-4-oxotetrahydrothiophen-2-yl)-5-nitro-1H-benzo[d]imidazol-1-yl)acetic acid
BT4		2-(5-bromo-2-(4-oxo-3-(p-tolyl)tetrahydrothiophen-2-yl)-1H-benzo[d]imidazol-1-yl)acetic acid
BT5		2-(5-fluoro-2-(3-(4-nitrophenyl)-4-oxotetrahydrothiophen-2-yl)-1H-benzo[d]imidazol-1-yl)acetic acid
BT6		2-(2-(3-(4-chlorophenyl)-4-oxotetrahydrothiophen-2-yl)-5-methyl-1H-benzo[d]imidazol-1-yl)acetic acid
BT­7		2-(5-hydroxy-2-(4-oxo-3-phenyltetrahydrothiophen-2-yl)-1H-benzo[d]imidazol-1-yl)acetic acid
BT8		2-(2-(3-(4-fluorophenyl)-4-oxotetrahydrothiophen-2-yl)-5-methoxy-1H-benzo[d]imidazol-1-yl)acetic acid

 

Table No: 3  IUPAC names of the synthesized compounds. (BTU)

BTU1		5-(1H-benzo[d]imidazol-2-yl)-4-(furan-2-yl)dihydrothiophen-3(2H)-one
BTU2		5-(5-chloro-1H-benzo[d]imidazol-2-yl)-4-(4 hydroxyphenyl) dihydrothiophen-3(2H)-one
BTU3		4-(4-methoxyphenyl)-5-(5-nitro-1H-benzo[d]imidazol-2-yl) dihydrothiophen-3(2H)-one
BTU4		5-(5-bromo-1H-benzo[d]imidazol-2-yl)-4-(p-tolyl)dihydrothiophen-3(2H)-one
BTU5		5-(5-fluoro-1H-benzo[d]imidazol-2-yl)-4-(4-nitrophenyl) dihydrothiophen-3(2H)-one
BTU6		4-(4-chlorophenyl)-5-(5-methyl-1H-benzo[d]imidazol-2-yl) dihydrothiophen-3(2H)-one
BTU­7		5-(5-hydroxy-1H-benzo[d]imidazol-2-yl)-4-phenyldihydrothiophen-3(2H)-one
BTU8		4-(4-fluorophenyl)-5-(5-methoxy-1H-benzo[d]imidazol-2-yl)dihydrothiophen-3(2H)-one

 

Table No: 4 IUPAC names of the synthesized compounds. (BTP)

BTP1		4-(furan-2-yl)-5-(1-(2-(piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)dihydrothiophen-3(2H)-one
BTP2		5-(5-chloro-1-(2-(piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)-4-(4-hydroxyphenyl) dihydrothiophen-3(2H)-one
BTP3		4-(4-methoxyphenyl)-5-(5-nitro-1-(2-(piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl) dihydrothiophen-3(2H)-one
BTP4		5-(5-bromo-1-(2-(piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)-4-(p-tolyl)dihydrothiophen-3(2H)-one
BTP5		5-(5-fluoro-1-(2-(piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)-4-(4-nitrophenyl) dihydrothiophen-3(2H)-one
BTP6		4-(4-chlorophenyl)-5-(5-methyl-1-(2-(piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)dihydrothiophen-3(2H)-one
BTP­7		5-(5-hydroxy-1-(2-(piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)-4-phenyldihydrothiophen-3(2H)-one
BTP8		4-(4-fluorophenyl)-5-(5-methoxy-1-(2-(piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl) dihydrothiophen-3(2H)-one

 

Table No: 5 IUPAC names of the synthesized compounds.  (BTPB)

BTPB1		5-(1-(2-(4-(2-chlorophenyl) piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)-4-phenyldihydrothiophen-3(2H)-one
BTPB2		4-phenyl-5-(1-(2-(4-phenylpiperazin -1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)dihydrothiophen-3(2H)-one
BTPB3		5-(1-(2-(4-(4-nitrophenyl)piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)-4-phenyldihydrothiophen-3(2H)-one
BTPB4		4-phenyl-5-(1-(2-(4-phenylpiperazin -1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)dihydrothiophen-3(2H)-one
BTPB5		5-(5-fluoro-1-(2-(4-phenylpiperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2-yl)-4-phenyldihydrothiophen-3(2H)-one

 

 

 

RESULT AND DISCUSSION:

The title compounds (BC¹-BTPB⁵) (Thirty seven compounds) were prepared from 2(2-substituted phenyl ethenyl) 1H benzimidazole by various steps. The structures of the compounds were confirmed by spectra and analytical studies. All the compounds synthesized matched with spectral data. The compounds synthesized were screened mainly for the antitubercular activity by using middle brook 7H9 broth base media method using H37Rv strain. Compounds  BC₂, BC₄, BC₅, BC₆, BC₈BT₂, BT₄, BT₅, BT₆, BT₈, BTU₂, BTU₄, BTU₅, BTU₆, BTU₈, BTP₂, BTP₄, BTP₅, BTP₆, BTP₈, BTPB_2-5, have shown  Very -significant antitubercular activity. Whereas other compounds shown moderate antitubercular activity. H₃₇Rv strain was used as standard tubercular organism. Streptomycin was used as standard drug.

 

Compounds BC_5, BC_7, BC₈ and BT_5, BT₈, BTU₅, BTU₆, BTU₈, BTP₄, BTP₅, BTP₆, BTP₈, BTPB_1-5   have shown significant anti bacterial activity against E-coil, while other compound showed moderate activity. Ciprofloxacin was used as standard drug. Compounds BC_4, BC_6, BC₈, BT₅, BT₆, BTU₄, BTU₅, BTU₆, BTP₇, BTP₈, BTPB_1-5 have shown significant antifungal activity against C. albicans, while other compounds show moderate activity. Fluconazole was used as standard drug.

 

CONCLUSION:

Benzimidazole analogs bearing electron-withdrawing as well as electron-donating substituent were synthesized, in order to achieve bioactive molecules with significant antimicrobial property. The desired compounds were prepared by multi-step synthesis process. The formation of intermediates and their corresponding derivatives was confirmed by spectral characterization such as ¹H NMR, IR and elemental analysis. The compounds were screened for their antimicrobial properties. From the SAR studies data; it was observed that the derivatives with electron-withdrawing functional groups were more bio-active than that with electron-donating functional groups. Material Science study ,Bioluminate Compound structure study,Compound Stereo view with numbering and 3D Structure Scupling, Ramachandran plot study  will be done under QSAR.

 

REFERENCES:

1.       Dhawas A.K.,Thakare S.S., “Synthesis of some new Imidazole-2-thiols and their derivatives as as potent antimicrobial agents” Indian Journal of Chemistry 2014; Vol 53(B):642-646.

2.       T Mohan Das,Chebrolu Rao, ‘Synthesis and Crystallographic Characterization of some derivatives of benzimidazole’ Indian Journal of Chemistry 2003; Vol 42(B):661-665.

3.       Dubey P.K., Kumar C.R.,  “Synthesis  1-alkyl-2substituted 2-pyridyl benzimidazole”, Indian Journal of Chemistry 2003 ;Vol  42(B): 2115-2118.

 

 

 

 

Accepted on 27.09.2018        © RJPT All right reserved

Research J. Pharm. and Tech 2018; 11(12): 5385-5393.