Design, Synthesis and Comparative Study of Anti-Microbial Activities on Barbituric Acid and Thiobarbituric Acid based Chalcone Derivatives Bearing the Pyrimidine Nucleus

A new comparative series of barbituric acid and thiobarbituric acid based chalcone derivatives bearing the pyrimidine nucleus were synthesized. The chemical structures of the resulting molecules were characterised by means of FT-IR (Fourier Transform Infrared) 1H NMR, 13C-NMR (Nuclear Magnetic Resonance) and HMBC (Heteronuclear Multiple-Bond Correlation) and Elemental Analysis. All synthesized compounds were subjected to in vitro antimicrobial screening against four bacterial strains i.e., one Gram Positive (Bacillus subtilis MTCC 441), two Gram Negative (E. coli MTCC 443, P. aeruginosa MTCC 1688), and one Fungal (C. albicans MTCC 227) Strains. The structure activity relationship is discussed on the basis of bioactivity results, various functional groups present and position of the functional group at various positions of the synthesized compounds. The comparative antimicrobial activity study of both of the series elucidated that shows the chalcone compounds containing -thioketo group are more potent than the -keto group. very versatile as physiologically active compounds and substrates for the evaluation of various organic syntheses. So, in light of above facts of pyrimidine, barbituric acid, thiobarbituric acid and chalcones, we continue our earlier work on synthesis of 5-acetyl barbituric acid 4 and 5-acetyl thiobarbituric acid 4’ based chalcones 5 (a-k) and 5 (a’-k’). All the analogs were screened for their antimicrobial activity and their comparative results are discussed with respect to one Gram Positive (Bacillus subtilis MTCC 441), two Gram Negative (E. coli MTCC 443, P. aeruginosa MTCC 1688), and one Fungal (C. albicans MTCC 227) Species and effects of functional groups and position of functional groups on various microbial strains. Experimental Methods Chemicals and solvents were obtained from commercial sources and used as received throughout the investigation. Melting points were determined in open capillaries on a Veego electronic apparatus VMP-D (Veego Instrument Corporation, Mumbai, India) and are uncorrected. IR spectra (4000-400 cm-1) of synthesized compounds were recorded on a Perkin Elmer-Spectrum RX-IFTIR spectrophotometer using KBr pellets. Thin layer chromatography was performed on object glass slides (2 × 7.5 cm) coated with silica gel-G and spots were visualized under UV irradiation. 1H NMR and 13C NMR spectra were recorded on an Advance-II (Bruker) model using DMSO as a solvent and TMS as internal standard with 1H resonant frequency of 400 MHz and 13C resonant frequency of 100 MHz. The 1H NMR and 13C NMR chemical shifts were reported as parts per million (ppm) downfield from TMS Page 2 of 9 Citation: Dhorajiya BD, Bhuva RG, Dholakiya BZ (2016) Design, Synthesis and Comparative Study of Anti-Microbial Activities on Barbituric Acid and Thiobarbituric Acid based Chalcone Derivatives Bearing the Pyrimidine Nucleus. Chem Sci J 7: 126. doi:10.4172/2150-3494.1000126 Volume 7 • Issue 2 • 1000126 Chem Sci J ISSN: 2150-3494 CSJ, an open access journal (Me4Si). The splitting patterns are designated as follows; s, singlet; br s, broad singlet; d, doublet; t, triplet; q, quartet; m, multiplet. All standard strains for screening of antibacterial and antifungal activities were procured from Institute of Microbial Technology, Chandigarh. DMSO was used as diluents/vehicle to get desired concentration of drugs to test upon Standard bacterial strains. Synthesis of barbituric acid (3) To a solution of diethylmalonate 1 (20 g, 118.9 mmol), urea 2 in methanol, anhydrous sodium methoxide was added and refluxed at 65°C for 8 h. A white solid separates. Then in above reaction mixture 125 ml. of hot (50°C) water was added and hydrochloric acid was used to make the solution acidic. After completion of the reaction, the resulting clear solution was filtered and cooled in an ice bath overnight. The white product formed and it was filtered, washed with 50 ml of cold water, dried and recrystallized from acetone to afford compound 3 as a white powder [18-20]. Synthesis of thiobarbituric acid (3’) To a solution of diethylmalonate 1 (20 g, 118.9 mmol), thiourea 2’ (7.5 g, 125 mmol) in methanol, anhydrous sodium methoxide was added and refluxed at 65°C for 8 h. A white solid separates. Then in above reaction mixture 125 ml of hot (50°C) water was added and hydrochloric acid was used to make the solution acidic. After completion of the reaction, the resulting clear solution was filtered and cooled in an ice bath overnight. The white product formed and it was filtered, washed with 50 ml of cold water, dried and recrystallized from acetone to afford compound 3’ as a Light yellowish white powder [18-20]. Synthesis of 5-acetyl barbituric acid (4) To a solution of barbituric acid (3) (6.4 g, 44.39 mmol) in acetic anhydride (150 ml), few drops of H2SO4 was added and refluxed for 1 h. The reaction in the beginning was a suspension but after about 10 min of refluxed, it changes to orange /brown color clear solution. The reaction mixture was concentrated into 1/2 of its original volume and cooled at about 10°C. The solid product was formed, filtered, washed with hot water then acetone, and dried to give compound 4 as a yellow powder [21]. Synthesis of 5-acetyl thiobarbituric acid (4’) To a solution of barbituric acid (3) and thiobarbituric acid (3’) (6.4 g, 44.39 mmol) in acetic anhydride (150 ml), few drops of H2SO4 was added and refluxed for 1 h. The reaction in the beginning was a suspension but after about 10 min of refluxed, it changes to orange/ brown color clear solution. The reaction mixture was concentrated into 1/2 of its original volume and cooled at about 10°C. The solid product was formed, filtered, washed with hot water then acetone, dried to give compound 4 and 4’ as a brown powder [21]. General synthetic procedure for the barbituric acid based chalcone compounds 5 (a-k) To a well stirred solution of compound 5-acetyl barbituric acid (4) in 40% aqueous sodium hydroxide solution, equimolecular amount of the appropriate aldehydes were was added. The reaction mixture was stirred at room temperature for about 12 h. The confirmation of the reaction was carried out by TLC using chloroform-methanol and Hexane-Ethyl acetate (4:1 v/v) mixture. After completion of the reaction, final compound was isolated from water at 6-7 pH. Further purification of isolated compound was done by recrystallization in methanol. Similarly other compounds 5 (a-k) were synthesized [22,23]. General synthetic procedure for the thiobarbituric acid based compounds 5 (a’-k’) To a well stirred solution of compound 5-acetyl thiobarbituric acid (4’) in 40% aqueous sodium hydroxide solution, equimolecular amount of the appropriate aldehydes were was added. The reaction mixture was stirred at room temperature for about 12 h. The confirmation of the reaction was carried out by TLC using chloroform-methanol and Hexane-Ethyl acetate (4:1 v/v) mixture. After completion of the reaction, final compound was isolated from water at 6-7 pH. Further purification of isolated compound was done by recrystallization in methanol. Similarly other compounds 5 (a’-k’) were synthesized [22,23].