Synthesis and Biological Evaluation of New Chalcone Analogs

 

H.V. Shahare*, G.R. Pawar, S.S. Patil and P.D. Patil

Department of Pharmaceutical Chemistry, SNJB’S Shriman Sureshdada Jain College of Pharmacy, Chandwad, Nashik, MS, India-423101

*Corresponding Author E-mail: hiteshshahare1@rediffmail.com

ABSTRACT:

The inevitable consequence of the widespread use of antimicrobial agents has been the emergence of antibiotic-resistant pathogens, fueling an ever-increasing need for new drugs. In an effort to develop antimicrobial agents, a series of chalcones were prepared by Claisen-Schmidt condensation of bromo and chloro acetophenone with appropriate aromatic aldehydes in the presence of aqueous solution of sodium hydroxide and ethanol at room temperature. The synthesized compounds were characterized by their physical constants, TLC, IR and NMR spectroscopy. Further all the synthesized compounds were successfully evaluated for their antibacterial and antifungal activities by cup-plate method.

 

 

 

INTRODUCTION:

Chalcones are well known intermediates for synthesizing various heterocyclic compounds. The compounds with the backbone of chalcones have been reported to possess various biological activities such as antimicrobial¹, antitubercular², anti-inflammatory³, analgesics⁴, anticancer⁵, antiplatelet⁶, antiviral⁷, antioxidant⁸, antiulcerative⁹, antihyperglycemic¹⁰, antileishmanial¹¹, antimalarials¹², and immunomodulatory¹³. The presence of reactive α, β unsaturated keto function in Chalcone is found to be responsible for their antimicrobial activity. These are also known as benzalacetophenone or phenyl styryl ketone. In the present investigation, we report the reaction of chloro-acetophenone and bromo-acetophenone with different aromatic aldehyde derivatives to form Chalcone. The structure of various synthesized compounds was elucidate on the basis of TLC, IR, and ¹H NMR spectral data.

 

MATERIAL AND METHOD:

All the chemicals used were obtained from S. D. Fine Chem. Ltd Mumbai. The agar medium, PDA medium was purchased from HI media Laboratories Ltd., Mumbai, India. All the chemicals were characterized for their purity. New Chalcone derivatives were synthesized and characterized by physical methods as reported in Table 1.

 

General procedure for synthesis of Chalcone:

Stir the mixture of 4-substituted acetophenone (0.01mol), substituted aromatic benzaldehyde (0.02mole) and solid NaOH pellet (100mg) in 5 mL water and 10 mL of ethanol for 30 min. The reaction mixture was then allowed to stand for 1hr. The precipitate product was filtered and purified by recrystallisation from ethanol (Scheme-1).

 

Biological evaluation:

Antibacterial activity:

The synthesized compounds of the series were screened for their antimicrobial activity against the growth of four bacteria by following cup plate method^{14, 15}. The bacteria used are Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis. Preparation of nutrient broth, subculture, agar medium and peptone water was done as per the standard procedure. Discs measuring 6.25 mm in diameter were punched from Whatmann No.1 filter paper. The test compounds were prepared in different concentrations using dimethylformamide.

 

Fig 1. General synthetic scheme of Chalcone derivatives:

 

Where R= Cl, Br, R’= OH, CH3, Cl, NO2, N (CH3)2, Napthyl, 4-hydroxy 3-methoxy

 

Table 1. Physical data of Chalcone derivatives (1-10)

Comp. no.	Starting material		M. P. [o C]	% yield	Rf value
1			73-75	79.18	0.827
2			116-119	74.90	0.759
3			147-149	70.83	0.621
4			85-89	79.41	0.962
5			189-194	86.73	0.845
6			80-83 o	66.28	0.621
7			142-145	86.80	0.657
8			70-73	75.56	0.725
9			150-153	69.50	0.671
10			80-83	72.26	0.589

 

Table 2. Antimicrobial activity of Chalcone derivatives (1-10)

Comp. no.	Name of compound	Area of inhibition (in mm)
		E. coli		Staph. aureus		Pseudononas aerogenosa		Bacillus subtilis
		0.05 mL	0.1 mL	0.05 mL	0.1 mL	0.05 mL	0.1 mL	0.05 mL	0.1 mL
1.	C15H13OCl	9	12	11	14	8	10	9	14
2.	C16H15Cl	9	-	11	-	7	8	8	11
3.	C15H12O2NCl	9	11	10	12	8	9	7	12
4.	C17H18NCl	8	-	8	-	7	9	9	-
5.	C19H15Cl	7	9	9	11	6	8	8	11
6.	C15H12BrCl	8	11	9	11	7	9	8	11
7.	C16H15Br	9	11	11	15	8	11	10	15
8.	C15H12O2NBr	10	14	11	16	8	11	10	14
9.	C17H18NBr	7	9	8	11	7	9	9	12
10.	C16H15O2Br	9	12	12	14	8	9	10	14
Std.	Ciprofloxacin	14	17	16	19	12	16	14	20

(-) indicates no zone of inhibition

 

Table 3. Antifungal activity of Chalcone derivatives (1-10)

Comp. no	Name of compound	Area of inhibition (in mm)
		A. niger		R. oryzae		A. flavis
		0.05 mL	0.1 mL	0.05 mL	0.1 mL	0.05 mL	0.1 mL
1.	C15H13OCl	9	11	9	12	8	12
2.	C16H15Cl	7	9	7	8	6	8
3.	C15H12O2NCl	6	8	7	9	6	9
4.	C17H18NCl	5	6	6	8	-	-
5.	C19H15Cl	6	7	6	8	6	9
6.	C15H12BrCl	7	9	7	9	5	10
7.	C16H15Br	9	11	8	12	8	11
8.	C15H12O2NBr	8	10	9	11	9	10
9.	C17H18NBr	7	9	5	6	-	-
10.	C16H15O2Br	6	8	7	9	8	10
Std.	Fluconazole	16	20	14	17	11	19

(-) indicates no zone of inhibition

 

 

The solutions of test compounds were prepared by dissolving 5mg of each in 5mL of DMF at a concentration of 1000ug/mL. Volumes of 0.05 mL and 0.1 mL of each compound were used for testing. The cups each of 9mm diameter were made by scooping out medium with a sterilized cork borer in a Petri dish which was streaked with the organism. The solutions of each test compound (0.05 and 0.1 mL) were added separately in the cups and Petri dishes were subsequently incubated. A reference standard for both gram positive and gram negative bacteria was made by dissolving accurately weighed quantity of Ciprofloxacin (200 and 1000ug/mL respectively) in sterile distilled water, separately. The incubation was carried out at 37°C for 24h. All the experiments were carried out in triplicate. Simultaneously, controls were maintained by employing 0.1 mL of DMF which did not reveal any inhibition. Zones of inhibition produced by each compound were measured in mm. The activities of the compound were compared with standard antibacterial (Ciprofloxacin) substances under same conditions are reported in Table 2.

 

Antifungal activity:

Synthesized compounds also tested for their antifungal activity using potato-dextrose-agar (PDA) medium by same cup and plate method against Aspergillus niger, Aspergillus flavus, Rhizopus oryzae. Preparation of nutrient broth, subculture, base layer medium and PDA medium was done as per the standard procedure. The solution of test compounds were prepared by a similar procedure described under the antibacterial activity. Each test compound was dissolved in 5 mL of DMF (1000ug/mL). Volumes of 0.05 and 0.1 mL of each compound were used for testing. A reference standard drug Fluconazole (200 and 1000ug/mL, respectively) and DMF as a control which did not reveal any inhibition. The experiments were performed in triplicate in order to minimize the errors. Zone of inhibition produced by each compound was measured in mm. the results of antifungal activities are reported in Table 3.

 

RESULT AND DISSCUSSION:

The purity and structure of synthesized compounds were confirmed by thin layer chromatography, melting point, IR and 1H NMR spectroscopy. IR spectra were recorded by using Jasco FTIR 4100 spectrophotometer. ¹H NMR spectra were recorded by using TMS as an internal standard. Melting points were determined in open capillary tube method and are uncorrected.

 

SPECTRAL DATA:

Compound 1: (E)-4-(3-(4-chlorophenyl) prop-1-enyl) phenol:

IR (cm^-1): 1730 (C=O), 1634 (CH=CH), 856 (C-Cl), 3436 (OH); ¹H NMR (δ ppm): 7.28-7.70 (8H, m, Ar-H), 7.79 (1H, d, Ar-CH=), 7.33 (1H, d, CO-CH=) 12.50 (1H, s, OH).

Compound 2: (E)-1-(3-(4-chlorophenyl) prop-1-enyl)-4-methylbenzene:

IR (cm^-1): 1734 (C=O), 1631 (CH=CH), 852 (C-Cl); ¹H NMR (δ ppm): 7.32-7.73 (8H, m, Ar-H), 7.72 (1H, d, Ar-CH=), 7.35 (1H, d, CO-CH=), 2.38 (3H, s, Ar-CH₃)

 

Compound 3: (E)-1-(3-(4-chlorophenyl) prop-1-enyl)-4-nitrobenzene:

IR (cm^-1): 1696 (C=O), 1642 (CH=CH), 848 (C-Cl), 1524 (C-NO₂); ¹H NMR (δ ppm): 7.28-7.70 (8H, m, Ar-H), 7.79 (1H, d, Ar-CH=), 7.33 (1H, d, CO-CH=).

 

Compound4: (E)-4-(3-(4-chlorophenyl) prop-1-enyl)-N, N-dimethylbenzenamine:

IR (cm^-1): 1658 (C=O), 1574 (CH=CH), 864 (C-Cl); ¹H NMR (δ ppm): 7.16-7.60 (8H, m, Ar-H), 7.86 (1H, d, Ar-CH=), 7.23 (1H, d, CO-CH=).

 

Compound 5: E)-1-(3-(4-chlorophenyl) prop-1-enyl) naphthalene:

IR (cm^-1): 1720 (C=O), 1648 (CH=CH), 854 (C-Cl); ¹H NMR (δ ppm): 7.12-7.94 (10H, m, Ar-H), 7.84 (1H, d, Ar-CH=), 7.08 (1H, d, CO-CH=).

 

Compound 6: 1-(2-chlorocinnamyl)-4-bromobenzene:

IR (cm^-1): 1724 (C=O), 1644 (CH=CH), 858 (C-Cl), 832 (C-Br); ¹H NMR (δ ppm): 7.33-7.72 (8H, m, Ar-H), 7.81 (1H, d, Ar-CH=), 7.12 (1H, d, CO-CH=).

 

Compound 7: (E)-1-(3-(4-bromophenyl) prop-1-enyl)-4-methylbenzene:

IR (cm^-1): 1734 (C=O), 1631 (CH=CH), 838 (C-Br); ¹H NMR (δ ppm): 7.22-7.62 (8H, m, Ar-H), 7.82 (1H, d, Ar-CH=), 7.23 (1H, d, CO-CH=), 2.36 (3H, s, Ar-CH₃)

 

Compound 8: (E)-1-(3-(4-bromophenyl) prop-1-enyl)-4-nitrobenzene:

IR (cm^-1): 1666 (C=O), 1632 (CH=CH), 826 (C-Br), 1498 (C-NO₂); ¹H NMR (δ ppm): 7.28-7.70 (8H, m, Ar-H), 7.79 (1H, d, Ar-CH=), 7.33 (1H, d, CO-CH=).

 

Compound9:(E)-4-(3-(4-bromophenyl) prop-1-enyl)-N, N-dimethylbenzenamine:

IR (cm^-1): 1642 (C=O), 1596 (CH=CH), 822 (C-Br); ¹H NMR (δ ppm): 7.20-7.84 (8H, m, Ar-H), 7.22 (1H, d, Ar-CH=), 7.14 (1H, d, CO-CH=).

 

Compound 10: (E)-4-(3-(4-bromophenyl) prop-1-enyl)-4-hydroxy, 3-methoxy benzene:

IR (cm^-1): 1658 (C=O), 1562 (CH=CH), 3422 (OH), 861 (C- Br); ¹H NMR (δ ppm): 7.16-7.60 (8H, m, Ar-H), 7.86 (1H, d, Ar-CH=), 7.23 (1H, d, CO-CH=) 12.46 (1H, s, OH), 3.90 (3H, s, OCH₃).

 

CONCLUSION:

A new series of p-bromo and p-chloro chalcone analogs were synthesized successfully by simple method. All synthesized successfully Chalcone analogs were successfully characterized by their physical constant, TLC and IR. Also they were evaluated for their antibacterial and antifungal activity. These results suggested that the Chalcone derivatives have excellent scope for further development as commercial antimicrobial agents.

 

ACKNOWLEDGEMENT:

The authors are thankful to Dr. C. D. Upasani, Principal of SSDJ College of Pharmacy, Chandwad, Nashik [MS] for regular guidance and providing the facility for experimental work. Also authors are thankful to UICT Mumbai for providing NMR facilities.

 

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Received on 14.09.2010        Modified on 19.09.2010

Accepted on 25.09.2010        © AJRC All right reserved