INTRODUCTION:

Antibiotics are one of our most important weapons in fighting bacterial infections and have greatly benefited the health-related quality of human life since their introduction The increasing incidence of infection caused by the rapid development of bacterial resistance to most of the known antibiotics is a serious health problem¹. While many factors may be responsible for mutations in microbial genomes, it has been widely demonstrated that the incorrect use of antibiotics can greatly increase the development of resistant genotypes. As multidrug-resistant bacterial strains proliferate, the necessity for effective therapy has stimulated research into the design and synthesis of novel antimicrobial molecules. Isolation, identification and application of organo-sulphur and nitrogen containing compounds resulted in their useful scientific, technical and industrial growth, which has led to the development of heterocyclic chemistry during the last two decades^2-3.Vulcanization of rubber, hair curling, muscle contraction, natural aromas, vitamins, hormones, antibiotics, radio protective agents, dye stuffs, binding materials, proteins and polypeptides etc. are well known application of sulphur and nitrogen containing compounds.

Thiazole are the great biological importance. This ring system occurs in thiamin (thiamine, Vit B1), the bacitracin and penicillin antibiotics (from a bacterium and a mold, respectively), Nocathiacins, a thiazole peptide class of antibiotics⁴. The past study shows that 2,4 thiazolidinedoine nucleus is very stable and the derivatives of 2,4 thiazolidinedoine exhibit a wide spectrum of biological activities like antidibetic, antibacterial, antifungal, antiiflamatory, anti HIV, anticouvulsants, and cardiotonic activites^5-11.

Thus the basis of our research programmed was centered on the introduction of benzylidine moieties at the C-5 position of the thiazolidinedione ring and screening for antimicrobial activity.

Experimental Work:

ANTIMICROBIAL ACTIVITY:

Antibacterial and antifungal activities of the compounds were assessed by in vitro growth inhibitory activity against Escherichia coli, Staphylococcus aureus, Asperigillus niger, Candida albicans by using the disc diffusion method^12-13. The compounds to be tested were dissolved in DMF to final concentrations 50 μg per ml soaked in filter paper (Whatman No 4) discs of 6 mm diameter and the discs were placed on the already bacterial and fungal seeded plates and incubated at 35 ± 2°C for 48 h. Amikacin disc and ketoconazole disc were used as standard antibacterial drug and antifungal drugs. The inhibition zones were measured after subtracting inhibition due to solvent used.

EXPERIMENTAL:

The melting points of the synthesized compounds were determined by open capillary tube method and results were uncorrected. The purity of compounds were checked by TLC using silica gel G as an adsorbent, Ethyl acetate: Butanol: CHCl₃(1:2:1) were used as mobile phase. The spot was visualized by Iodine vapour. The structures of the synthesized compounds were characterized by IR and H-NMR spectral analysis in which it complies with the normal values. IR spectra’s in KBR were recorded on a FT-IR Spectrophotometer (shimadzu) and ¹H-NMR spectra’s were recorded on a bruker 300 AV spectrophotometer using TMS as an internal standard.

2, 4 Thiazolodine dione[I]:

In a 250 ml three necked flask a solution containing 56.4 gms. (0.6 mole) of chloroacetic acid in 60 ml of water and 45.6 gms (0.6 mole) of thiourea dissolved in 60 ml of water. The mixture was stirred for 15 minutes to form a white precipitate, accompanied by considerable cooling. To the contents of the flask was now added slowly 60 ml. concentrated hydrochloric acid from dropping funnel, the flask was connected with a reflux condenser and gentle heat applied to effect complete solution, after which the reaction mixture was stirred and refluxed for 8-10 hrs at 100-110⁰C. On cooling the contents of the flask solidified to a mass of clusters of white needles.

The product was filtered and washed with water to remove traces of hydrochloric acid and dried. It is re-crystallized from ethyl alcohol. The yield 85%; m.p 123-125 C; IR (KBr, cm^-1): 3145.68 (N H), 1753.17 (CO); 1H NMR (CDCl₃): 3.8 (s, 2H, methylene), 8.5 (s, 1H, imide).

5( 4-chlorobenzylidine) 2, 4 thiazolidinedione [II]:

In a 250 ml 3-necked round bottomed flask attached with a dean stark apparatus, Chlorobenzaldehyde (20 gm, 0.188 mole) and 2,4-thiazolidinedione (22 gm, 0.188 mole) were taken and suspended in dry toluene. To this catalytic amount of piperdine (1ml) was added. The mixture was stirred and refluxed. After the complete removal of water and when the temp. reached above 110 C the reaction mixture was stirred for 1 hr. On cooling the product precipitated in toluene. The compound was filtered and washed with cold dry toluene and dry ethanol. The yield 89%; m.p 185-187 C; IR (KBr, cm^-1): 3145.57 (N H), 1753.20 (CO), 1608.52 (C=C), 742.54 (Cl); 1H NMR (CDCl₃): 6.9-7.3 (m, 4H, aromatic), 7.5 (s, 1H, ethylene), 8.5 (s, 1H, imide).

5 (4-(4 substituted) Amino benzylidine) 2, 4- thiazolidinedione derivatives [III]:

0.01 mole of 4-chlorobenzylidine 2, 4 thiazolidinedione (2) and substituted primary amines (0.01 mol) was refluxed in 4 ml of dry pyridine and 20 ml of acetic anhydride for 4 hrs. The excess solvent was distilled off. The mixture was cooled and poured into crushed ice. The product was filtered and recrystallized from the ethanol.

5(4-(4-amino toluene) benzylidine)thiazolidine-2,4-dione [IIIa]:

The yield 65.30%; m.p 215-217°C; IR (KBr, cm^-1): 3147.61 (NH), 1753.17 (CO), 1608.52 and 1550.66 and 1455.56 (C=C Ar), 2942.54 (CH aliphatic); 1H NMR (CDCl₃): 2.3 (s, 3H, CH₃), 4.1(s,1H ,NH),6.7-7.3 (m, 8H, aromatic), 7.5 (s, 1H,ethylene), 8.5 (s, 1H, imide).

5(4-(4-aminobenzoic acid)benzylidine) thiazolidine-2,4-dione [IIIb].

The yield 71.20%; m.p 218-220°C; IR (KBr, cm^-1): 3470.47 (OH), 3145.68 (NH), 1755.10 (CO), 1608.52 and 1550.66 and 1455.56 (C=C Ar); 1H NMR (CDCl₃): 4.1(s,1H ,NH), 6.5-7.2 (m, 8H, aromatic), 7.6 (s, 1H,ethylene), 8.7 (s, 1H, imide),10.2 (s,1H, OH (carboxylic acid)).

5(4-(4-amino pyridine)benzylidine) thiazolidine-2,4-dione [IIIc].The yield 67.20%; m.p 227-228°C; IR (KBr, cm^-1): 3149.54 (NH), 1753.17 (CO), 1608.52 and 1550.66 and 1455.56 (C=C Ar); 1H NMR (CDCl₃): 4.1(s,1H ,NH), 6.5-7.2 (m, 8H, aromatic), 7.5 (s, 1H,ethylene), 8.5 (s, 1H, imide).

5(4-(4-amino(hydroxyphenyl))benzylidine) thiazolidine-2,4-dione [IIId].

The yield 75.10%; m.p 210-211 C; IR (KBr, cm^-1): 3363.80 (OH), 3149.54 (NH), 1753.17 (CO), 1608.52 and 1550.66 and 1455.56 (C=C Ar); 1H NMR (CDCl₃): 4.1(s,1H ,NH), 5.1 (s,1H, OH ). 6.6-7.1 (m, 8H, aromatic), 7.6 (s, 1H,ethylene), 8.8 (s, 1H, imide).

RESULT:

The results indicate that most all compounds exhibited significant antibacterial activity against Staphylococcus aureus and Escherichia coli (Table-1, Fig-1), while weak antifungal activity against Asperigillus niger and Candida albicans (Table-2, Fig-2).

Table1: Antibacterial activity of derivatives

Sr. No.	Compounds	Zone of inhibition (in mm.)
Sr. No.	Compounds	*E. coli*	*S. aureus*
1	IIIa	16	14
2	IIIb	15	12
3	IIIc	13	9
4	IIId	14	12
5	DMSO	0	0
6	AMIKACIN	18	17

Fig.1-

Table2: Antifungal activity of derivatives

Sr. No.	Compounds	Zone of inhibition (in mm.)
Sr. No.	Compounds	*Asperigillus niger*	*Candida albicans*
1	IIIa	09	02
2	IIIb	10	03
3	IIIc	11	05
4	IIId	10	04
6	DMSO	0	0
7	KETOCONAZOLE	20	10

Fig.2-

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Received on 21.04.2010 Modified on 12.05.2010

Asian J. Research Chem. 4(1): January 2011; Page 40-43