Designing and Synthesis of some Novel 2-Substituted Benzimidazole Derivatives and their Evaluation for Antimicrobial and Anthelmintic Activity

 

Chaitanya Prasad Meher*, Abinash Kumar Sahu, Srimanta Kumar Dash, Ranjan Kumar Sahoo, Subodha Chandra Sahu, Dillip Kumar Gupta

Department of Pharmaceutical Chemistry, The Pharmaceutical College (TPC), Tingipali, Barpali, Odisha

*Corresponding Author E-mail: chaitanyameher84@gmail.com

Objective: To design, synthesis & evaluation of 2-substituted benzimidazole derivatives for antimicrobial & anthelmintic activity. Method: The presented investigation is designed to upgrading the modest and comfortable method for development of numerous 2-substituted benzimidazole derivatives. It involves reaction of different derivatives of benzaldehyde with the benzimidazole. The synthesized compounds were subjected to software chem sketch, Molinspiration and FTIR. The synthesized compounds were investigated for antimicrobial activity by minimum inhibitory concentration & zone of inhibition method while anthelmintic activity by using Pheretima posthuma. Result: The 2-substituted benzimidazole derivatives were synthesized by unadventurous method. All the synthesized compounds displayed a characteristic peak in FTIR. It was found that the synthesized compounds showed appreciable antimicrobial as well as anthelmintic activity. Conclusion: It manifest a preferable synthetic procedure for benzimidazole derivatives which may attract the scientist in future for generation of newer antimicrobial & anthelmintic medication.

 

 

 

 

INTRODUCTION:

Benzimidazole have a high rank or status in the field of pharmaceutical chemistry. The unification of benzene and imidazole form benzimidazole [1]. The manipulation of Benzimidazole has been existing many years back [2].The area of the synthesis of these rings continues to grow, and the pharmaceutical chemistry will provide more and better approach for the synthetic thinking of this interesting heterocyclic nucleus, allowing the break through of new physic candidate having more active, more specific with safer properties. Benzimidazole nucleus with substitution were found to possess a wide receiver of pharmacologic action [3] i.e. antiviral, anti-helmenthic analgesic, anti inflammatory, antibacterial, antifungal, , anticonvulsant , anticancer , antiulcer, antihypertensive etc. [4]

 

MATERIALS AND METHODS:

All the chemicals used are of analytical grade. The software used are Molinspiration and Chemsketch.

 

 

Step-1: Equimolar quantities (0.01mol) of o-phenylenediamine (OPD), p-amino benzoic acid (0.01mol) in 4N HCl (20 ml) was refluxed for 30 min. The mixture is cooled and filtered off. End point of the reaction was determined through TLC. The obtained product was recrystallized from absolute alcohol.

 

Step-II (A): Benzaldehyde (10mmol) was added to step-1 product (10 mmol) in ethanol solution of sodium hydroxide (75 mmol sodium hydroxide in 40 ml of ethanol). The reaction mixture was subsequently stirred at room temperature for 5h and neutralized with a solution of 30% acetic acid leading to a precipitate. It was filtered, dried and recrystallized in toluene to get the pure compound.

 

Step-II(B):4-(dimethylamino) benzaldehyde (10mmol) was added to step-1 product ( 10 mmol) in ethanol solution of sodium hydroxide (75 mmol sodium hydroxide in 40 ml of ethanol). The reaction mixture was subsequently stirred at room temperature for 5h and neutralized with a solution of 30% acetic acid leading to a precipitate. It was filtered, dried and recrystallized in toluene to get the pure compound.

 

Step-II(C):4-methylbenzaldehyde (10mmol) was added to step-1 product (10 mmol) in ethanol solution of sodium hydroxide (75 mmol sodium hydroxide in 40 ml of ethanol). The reaction mixture was subsequently stirred at room temperature for 5h and neutralized with a solution of 30% acetic acid leading to a precipitate. It was filtered, dried and recrystallized in toluene to get the pure compound.

 

Step-II(D):4-methoxybenzaldehyde (10mmol) was added to step-1 product (10 mmol) in ethanol solution of sodium hydroxide (75 mmol sodium hydroxide in 40 ml of ethanol). The reactionmixture was subsequently stirred at room temperature for 5h and neutralized with a solution of 30% acetic acid leading to a precipitate. It was filtered, dried and recrystallized in toluene to get the pure compound.

 

 

RESULTS

Table 1: Properties of Synthesized compounds

Compound code	(A)	(B)	(C)	(D)
Molecular Formula	C20H15N3	C22H20N4	C21H17N3	C21H19N3O
Formula Weight	297.3532	340.421	311.37978	329.39506
Composition	C(80.78%) H(5.08%) N(14.13%)	C(77.62%) H(5.92%) N(16.46%)	C(81.00%) H(5.50%) N(13.49%)	C(76.57%) H(5.81%) N(12.76%) O(4.86%)
Molar Refractivity	93.68 ± 0.5 cm3	106.48 ± 0.5 cm3	98.10 ± 0.5 cm3	101.98 ± 0.3 cm3
Molar Volume	254.5 ± 7.0 cm3	295.7 ± 7.0 cm3	269.7 ± 7.0 cm3	264.5 ± 3.0 cm3
Parachor	666.6 ± 8.0 cm3	762.9 ± 8.0 cm3	697.7 ± 8.0 cm3	725.9 ± 4.0 cm3
Index of Refraction	1.657 ± 0.05	1.639 ± 0.05	1.647 ± 0.05	1.697 ± 0.02
Surface Tension	47.0 ± 7.0 dyne/cm	44.2 ± 7.0 dyne/cm	44.7 ± 7.0 dyne/cm	56.7 ± 3.0 dyne/cm
Density	1.16 ± 0.1 g/cm3	1.15 ± 0.1 g/cm3	1.15 ± 0.1 g/cm3	1.245 ± 0.06 g/cm3
Polarizability	37.13 ± 0.5 10-24cm3	42.21 ± 0.5 10-24cm3	38.89 ± 0.5 10-24cm3	40.43 ± 0.5 10-24cm3
Monoisotopic Mass	297.126597 Da	340.168797 Da	311.142248 Da	329.152812 Da
Nominal Mass	297 Da	340 Da	311 Da	329 Da
Average Mass	297.3532 Da	340.421 Da	311.3798 Da	329.3951 Da

 

Table 2: Biaoactive Properties

	Compound-A	Compound-B	Compound-C	Compound-D
GPCR ligand	-0.21	-0.17	-0.24	-0.24
Ion channel modulator	-0.34	-0.32	-0.41	-0.40
Kinase inhibitor	0.20	0.20	0.15	0.14
Nuclear receptor ligand	-0.31	-0.25	-0.33	-0.30
Protease inhibitor	-0.38	-0.34	-0.41	-0.39
Enzyme inhibitor	-0.03	-0.04	-0.10	-0.09

 

Table 3: Interpretation Chart

Comp. Code	IR DATA (cm-1)
(A)	1317 (C-H stretching, alkene), 3030 (C-H Stretching, aromatic), 750 (C-H Bending), 1646,1650,1654 (C-H Bending), 1411,1458, 1506,1552 (C=C Stretching, alkene), 3432 (N-H Stretching), 2257, 2240 (C=N Stretching)
(B)	2808,2915, 2962 (C-H Stretching alkane), 1317 (C-H stretching, alkene), 3030 (C-H Stretching, aromatic), 750 (C-H Bending), 1646,1650,1654 (C-H Bending), 1411,1458, 1506,1552 (C=C Stretching, alkene), 3432 (N-H Stretching), 2257, 2240 (C=N Stretching)
(C)	1317 (C-O Stretching), 2808,2915, 2962 (C-H Stretching alkane), 1317 (C-H stretching, alkene), 3030 (C-H Stretching, aromatic), 750 (C-H Bending), 1646,1650,1654 (C-H Bending), 1411,1458, 1506,1552 (C=C Stretching, alkene), 3432 (N-H Stretching), 2257, 2240 (C=N Stretching
(D)	2808,2915, 2962 (C-H Stretching alkane), 1317 (C-H stretching, alkene), 3030 (C-H Stretching, aromatic), 750 (C-H Bending), 1646,1650,1654 (C-H Bending), 1411,1458, 1506,1552 (C=C Stretching, alkene), 3432 (N-H Stretching), 2257, 2240 (C=N Stretching)

 

Fig 1: IR spectra of A

 

Fig 2: IR spectra of B

 

Fig 3: IR spectra of C

 

Fig 4: IR spectra of D

 

Anti bacterial activity chart:

Table4: Minimum inhibitory concentration chart

Compound code	Molecular  Formula		MIC			MIC
			E.coli  Conc. ( µg /ml)			S. aureus Conc. ( µg /ml)
			30	40	50	30	40	50
(A)		C20H15N3	+	-	-	+	-	-
(B)		C22H20N4	+	-	-	+	-	-
(C)		C21H17N3	+	-	-	+	-	-
(D)		C21H19N3O	+	-	-	+	-	-
STD(cipro. &Sulp.			_	-	-	-	-	-
Solvent		DMSO	0	0	0	0	0	0

+Ve=Turbidity observed, -Ve=Turbidity was not observed

 

Table 5: Zone of inhibition chart

Compound  Code	Molecular formula	ZONE OF INHIBITION (mm)			ZONE OF INHIBITION (mm)
		E.coli. conc.( µg /ml)			S.aureus  conc.( µg /ml)
		30	40	50	30	40	50
(A)	C20H15N3	8	9	10	8	9	9
(B)	C22H20N4	8	11	12	8	10	10
(C)	C21H17N3	7	8	8	8	10	11
(D)	C21H19N3O	8	8	9	10	12	13
STD	C18H19FN2O3	10	13	14	10	12	15
Solvent	DMF	0	0	0	0	0	0

 

 

Fig 5: Zone of inhibition of A (E.Coli)

Fig 6: Zone of inhibition of A (S.Aureus)

 

 

Fig 7: Zone of inhibition of B (E.Coli)

Fig 8:Zone of inhibition of B (S.Aureus)

 

 

Fig 9: Zone of inhibition of C (E.Coli)

Fig 10:Zone of inhibition of C (S.Aureus)

 

Fig 11: Zone of inhibition of D (E.Coli)

Fig 12: Zone of inhibition of D (S.Aureus)

 

Evaluation table for anthelmintic activity:

Table 6: Anthelmintic activity evaluation chart

S.N	Compound Code	Concentration  ( µg /ml)	Time taken for paralysis  (Min)	Time taken for death  (Min)
1	Albendazole  (Std.)	30	34.43 ± 2.00	00.57 ± 1.25
		40	31.40 ± 1.20	00.56 ± 1.30
		50	30.50 ± 1.00	00.55 ± 2.30
1	(A)	30	40.43 ± 1.21	01.05 ± 2.16
		40	38.40 ± 1.30	01.00 ± 1.21
		50	37.73 ± 1.22	00.58 ± 2.54
2	(B)	30	40.30 ± 1.22	01.02 ± 2.14
		40	39.25 ± 1.17	01.01 ± 1.25
		50	39.00 ± 2.01	0.57 ± 1.50
3	(C)	30	39.43 ± 1.30	01.05 ± 2.15
		40	35.45 ± 1.25	01.03 ± 1.20
		50	34.73 ± 2.12	0.55 ± 1.54
4	(D)	30	44.43 ± 1.26	01.05 ± 1.00
		40	40.10 ± 1.20	01.05 ± 1.45
		50	40.15 ± 1.01	0.58 ± 2.54

Values are expressed as mean ± SEM, n = 6.

DISCUSSION:

The synthesis of benzimidazole heterocycles that have been reported in this work gave different methodologies to the challenge of preparing these bioactive products and allows the synthesis of many novel benzimidazole chemical derivatives. In general, it was prepared by synthesis of benzimidazole nucleus, o-phenylenediamine (OPD), p-amino benzoic acid (0.01mol) in 4N HCl (20 ml) was refluxed for 30 min under laboratory conditions. The resulting product was treated with different kinds of aromatic aldehyde which resulted in the formation of different benzimidazole derivatives.

 

The structures of the synthesized compounds were confirmed on the basis of their FTIR data. The spectral data for FTIR was elaborated, which confirms the structure of synthesized compounds. Antibacterial activity data of all benzimidazole derivatives against tested organisms (E.coli and S.aureus) displayed significant activity. It was found that all compounds have shown significant antibacterial activity against these gram positive bacteria and gram negative bacteria.

 Minimum inhibitory concentration was found using different dilutions (30 µg/ml, 40 µg/ml, 50 µg/ml) of all synthesized compounds. All dilution were transferred into the dilution tubes containing nutrient media. Later on microorganisms (both gram+ve & gram-ve bacteria) were added. The turbidity was measured. Ciprofloxacin & sulphanilamide were used as standard & DMF as control. It was found that all the synthesized compounds showed turbidity in 30 µg/ml but no one showed turbidity in 40µg/ml & 50µg/ml. So from this it concluded that the minimum inhibitory concentration (MIC) of all our synthesized compound is 40 µg/ml.

 

Zone of inhibition was found using agar disc diffusion methods in which different dilution of our synthesized compound (30µg/ml, 40 µg/ml, 50 µg/ml) were prepared. Ciprofloxacin, sulphanilamide were used as standard & DMF as control. It was found that zone of inhibition was increased when we increased the concentration of the synthesized compound. Minimum zone of inhibition (7 mm) was found in case of compound, C (E.coli). Maximum zone of inhibition (13 mm) was found in case of compound D (S.aureus) followed by 11 mm in case of C (S.aureus).

 

Synthesized drugs were compared with one of the effective anthelmintic standard drug Albendazole with different concentration (30 µg/ml, 40 µg/ml, 50 µg/ml). When 30µg/ml solution of the standard albendazole & synthesized sample was tested then it was found that albendazole take 34.43 ± 2.00min for paralysis & 00.57 ± 1.25min for death whereas synthesized drugs (A, B, C & D) at the same concentration takes40.43 ± 1.21, 40.30 ± 1.22, 39.43 ± 1.30, 44.43 ± 1.26min respectively for paralysis &01.05 ± 2.16, 01.02 ± 2.14, 01.05 ± 2.15, 01.05 ± 1.00 min respectively for death. From this we can say that synthesized compound has definitely some anthelmintic activity. According to that when we increase the concentration of the synthesized compound the paralysis time as well as the death time also decreases accordingly.

 

The Bioactive properties were obtained using the software Molinspiration. Compound-A, B & C shows better activity against protease enzyme whereas Compound-D shows itself as an effective ion channel modulator. Protease inhibitors are used as a class of antiviral drugs. So the compounds (4-(1H-benzimidazol-2-yl-N-(E)- phenylmethylidene), (4-[(E)-{[4-(1H- benzimidazol-2-yl) phenyl] imino} methyl]-N,N-dimethylaniline), (4-(1H-benzimidazol-2-yl)-N-(E)-(4-methylphenyl)methylidene]aniline) may be used as antiviral drugs.

 

From above discussed matter it confirmed that all our synthesized benzimidazole derivatives have moderate antimicrobial activity as well as anthelmintic activity.

 

CONCLUSION:

The article presenting a simple method for designing & synthesis of 2-substituted Benzimidazole derivatives.Attaching of various aromatic aldehydeto benzimidazole nucleusresulting development of newer derivatives whichshowed little to moderate activity against gram+ve and gram–ve bacteria along with anthelmintic activity.

 

REFERENCES:

1.     Barker HA, Smyth RD, Weissbach H, Toohey JI, Ladd JN and Volcani BE. Isolation and properties of crystalline cobamide coenzymes containing Benzimidazole or 5, 6-Dimethylbenzimidazole. Journal of Biological Chemistry. 1960; 235; 480-88.

2.     Patil A, Ganguly S and Surana S. A systematic review of benzimidazole derivatives as an antiulcer agent. Rasayan J Chem 2008;447-60

3.     K F Ansari and C Lal, Synthesis and biological activity of some heterocyclic compounds containing benzimidazole and beta-lactam moiety, J Chem Sci, 2009; 1017–25.

4.     K Sreena, Synthesis and Anthelmintic Activity of Benzimidazole Derivatives Hygeia 09; 21-22

 

 

 

 

 

Received on 02.02.2019                    Modified on 20.02.2019

Accepted on 05.03.2019                   ©AJRC All right reserved