Antimicrobial Activities of some Synthesized Pyridines, Oxazines and Thiazoles from 3-Aryl-1-(2-naphthyl)prop-2-en-1-ones

3-Aryl-1-(2-naphthyl)-prop-2-en-1-ones were reacted with ethyl cyanoacetate to produce 4-aryl-6-(2-naphthyl)-2-oxo-1,2-dihydropyridine-3-carbonitriles, which were treated with ethyl chloroacetate to give the corresponding ester. Treatment of the latter ester with hydrazine hydrate or anthranilic acid afforded hydrazides and benzoxazines. The hydrazides were reacted with benzaldehyde or phenylisothiocyanate to afford the corresponding hydrazone and thiosemicarbazide derivatives, which were cyclized with chloroacetic acid or thioglycolic acid to the corresponding thiazole derivatives. 3-Aryl-1-(2-naphthyl)-prop-2-en-1-ones were either condensed with malononitrile under different conditions to produce carbonitrile derivatives or treated with active methylene reagents to afford the substituted cyclohexene derivatives. The structure assignment of the new compounds is based on chemical and spectroscopic evidence. Some of these compounds exhibited antimicrobial activities comparable to Ampicillin ® as reference drug. (c) and Yeast:


Antimicrobial evaluation
The newly synthesized heterocyclic compounds, shown in Table 1 were tested for their antimicrobial activity against the following microorganisms: Escherichia coli, Pseudomonas putide, Bacillus subtilis, Streptococcus lactis, Aspergillus niger, Penicillium sp. and Candida albicans. The preliminary screening of the investigated compounds was performed using the filter paper disc-diffusion method. The most active compounds were: 5b, 8b and 17b and the results are summarized in Table 1.    [16].
Physical and spectral data are shown in Tables 2 and 3.

Method B.
A mixture of 2a,b (1 mmol) and malononitrile (~0.1 g, 1 mmol) in 50 ml acetic acid in the presence of 1 g sodium acetate or ~0.1 g ammonium acetate was refluxed for 3 h. The reaction mixture was poured onto ice-water, the formed solid was filtered off, dried and crystallized the proper solvent to give 12a,b and 13a,b, respectively (Tables 2 and 3).

Antimicrobial screening
The newly synthesized heterocyclic compounds were tested for their antimicrobial activity against the following microorganisms: (a) Gram-negative:

Candida albicans
Mediums: Three types of specific media were used in this study: Medium (1): For bacteria (Nutrient Medium), consisting of (g/l distilled water): peptone, 5 and meat extract, 3. pH was adjusted to 7.0.
For solid media, 2% agar was added. All media were sterilized at 121°C for 20 minutes.

Procedure (Filter paper diffusion method) [17]
Proper concentrations of microbial suspensions were prepared from 1 (for bacteria to 3 (for yeast and fungi)-day-old liquid stock cultures incubated on a rotary shaker (100 rbm). In the case of fungi, 5 sterile glass beads were added to each culture flask. The mycelia were then subdivided by mechanical stirring at speed N o . with the test compounds (5 μg/disc). After the impregnated discs have been air dried, they were placed on the agar surface previously seeded with the organism to be tested. Discs were gently pressed with forceps to insure thorough contact with the media. Three discs were arranged per dish, suitably spaced apart, i.e. the discs should be separated by a distance that is equal to or slightly greater than the sum of the diameters of inhibition produced by each disc alone. Each test compound was conducted in triplicate. Plates were kept in the refrigerator at 5°C for 1 hour to permit good diffusion before transferring them to an incubator at 37°C for 24 hours for bacteria and at 30°C for 72 hours for yeast and fungi.

Conclusion
In order to reveal a potential activity of nine newly obtained compounds, they were tested on seven bacterial species: Escherichia coli, Pseudomonas putide, Bacillus subtilis, Streptococcus lactis, Aspergillus niger, Penicillium sp., Candida albicans. The obtained results are shown in Table 1. Many of the investigated derivatives presented interesting antibacterial activity.