Original Article SYNTHESIS AND CHARACTERIZATION OF NEW COUMARIN DERIVATIVES CONTAINING VARIOUS MOIETIES WITH ANTIBACTERIAL ACTIVITIES SHOKHAN JAMAL HAMID 1 , AMMAR A. RAZZAK MAHMOOD KUBBA 2* 1 Department of Pharmaceutical Chemistry, School of Pharmacy, Faculty of Medical Sciences, University of Sulaimani, Sulaimani Iraq, 2 Department of Pharmaceutical Chemistry, College of Pharmacy, University of Baghdad-Baghdad-IRAQ Email: kubbaammar1963@gmail.com Received: 03 Mar 2015 Revised and Accepted: 15 Jun 2015 ABSTRACT Objective: The purpose of this research is to evaluate the antibacterial activity of different moieties (Schiff bases, chalcones, hydrazones and hydrazinyl thiazole) derivatives, inserted at carbon 8 of 7-hydroxy-4-methyl coumarin, using in vitro, serial broth dilution method. Methods: A series of new coumarin derivatives, including (Schiff bases, chalcones, hydrazones and hydrazinyl thiazole), were prepared from 7- hydroxy-4-methyl coumarin, by insertion of the formyl group, at carbon number 8 using Duff reaction. The structure of the new synthesized derivatives elucidated and confirmed utilizing the corresponding analytical and spectroscopic data; including FT-IR, 13 C-NMR, and mass spectroscopy. All new coumarin derivatives have been screened for their preliminary antibacterial activity, by serial broth dilution method against two Gram-positive bacteria (Staphylococcus epidermidis and Staphylococcus hemolyticus) and two Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae). Results: All the synthesized compounds have been found to exhibit considerable antibacterial activity in vitro. Among all the derivatives, compound (5a), showed the highest rate of inhibition, against (Escherichia coli), while compound (6a), showed the greatest anti-bacterial activity against (Staphylococcus hemolyticus), each with minimum inhibitory concentration of (25µg/ml), and the highest MIC of 200 µg/ml for compound 2, against. Klebsiella pneumoniae. Conclusion: Our results displayed a substantial preliminary antibacterial activity of the new coumarin moieties, especially some hydrazones and chalcones at C8 of the coumarin nucleus, against Gram-positive and a Gram-negative bacteria with distinguished MIC. Keywords: Coumarin, Duff reaction, Chalcones, Hydrazones, Schiff base, Antibacterial activity. INTRODUCTION Coumarin itself is a natural product found in some plant sources, including the sweet clover and Tonka bean. Some coumarin derivatives have been found to be largely distributed in the plant kingdom [1]. It has an aromatic odor often flatteringly associated with the sweet fragrance of freshly mown hay; therefore, it was used as a flavoring agent [2]. The coumarins are of great interest due to their biological properties [3]. In actual, their physiological, bacteriostatic, and anti-tumor activity, makes these interesting compounds attractive for further backbone derivatization and screening as novel therapeutic agents [4]. Coumarin and its derivatives have been found to possess antimicrobial [5], antiviral [6], anti-inflammatory [7], antioxidant [8], anti-cancer [9], anticoagulant and enzyme inhibition activities [10]. Hence in the light of wide applications of coumarin derivatives, it was planned to synthesize new series of coumarin derivatives at C8 by using Duff reaction and preliminary screen for their antibacterial activity. MATERIALS AND METHODS The melting points were determined, by open capillary tubes on a Stuart/SMP3 melting point apparatus version 5.0 and were used uncorrected. The IR spectra were recorded, on a Perkin-Elmer FT-IR spectrometer using KBr disc. 13 C-NMR spectra, were recorded on a Bruker FT-NMR spectrophotometer-500 MHz, in SAIF (sophisticated analytical instrument facility), a research center in India/Chennai, in DMSO-d6 and CDCl3 solvent, using TMS, (tetra methyl silane) as an internal standard and the values are expressed in ppm (part per million). The mass spectra were recorded using Agilent Technology (HP), GC/MS model 5973 network mass selective detector. The purity of the synthesized compounds and the progress of the reaction was determined by Thin Layer Chromatography on aluminum silica gel 60 F254 (Merck) detected by UV (ultraviolet) light (254 nm). All the chemicals purchased were of analytical grade and were used without further purification unless otherwise stated. Synthesis of 7-hydroxy-4-methyl coumarin 1 [11] A solution of (0.01 mole, 1.1 g) resorcinol and (0.01 mole, 1.3 ml) ethyl acetoacetate was added drop wise over a period of 30 min, with continuous stirring to (10 ml) of concentrated sulfuric acid in an ice bath so that the temperature of the mixture did not rise above 10 ˚C. The reaction mixture was kept at room temperature for 3 hrs, and then poured with vigorous stirring into a mixture of ice and water. The precipitate was filtered off and washed with water, then after drying, recrystallized using ethanol to get the pure product. Creamy colored needles; yield: 78%; m. p. 181-183 ˚C; IR (KBr, cm -1 ): 3155(ʋ OH), 1789 (ʋ C=O), 1599 (ʋ C=C). Synthesis of 8-formyl-7-hydroxy-4-methyl coumarin 2 [12] A mixture of 7-hydroxy-4-methyl-coumarin (0.025 moles,5.1 g) and Hexamethylenetetramine (0.07 moles,9.8 g) in glacial acetic acid (40 ml) was heated at 85-90 C˚ on a water bath for 7 hrs The hexamine adduct so formed was hydrolyzed with 20% HCl (75 ml), and the mixture was heated for another 30 min. After cooling, the reaction mixture was extracted with diethyl ether (50 ml) twice, and the ether layer was evaporated by using a rotary evaporator. The yellow colored crystals obtained which was recrystallized from ethanol. Pale yellow colored crystals; yield: 22%; m. p. 177-179 ˚C; IR (KBr, cm -1 ): 3437 (ʋ OH), 1745 (ʋ C=O, lactone), 1644 (ʋ C=O, aldehyde), 1594 (ʋ C=C); 13 C-NMR (CDCl3, δ ppm): 193.4 (C=O aldehyde), 165.3 (C=O lactone), 159.2, 156.1, 152.7, 132.9, 114.3, 112.1, 111.9, 108.7 (C aromatic and alkene),18.9 (CH3); MS m/z (%): 204 (96) [M] + , 176 (84), 175 (91), 147 (68), 143 (11),130 (17). Synthesis of aromatic amine Schiff bases 3a-c [13] To a solution of (0.01 mole) compound (2) in (25 ml) absolute ethanol, an appropriate aromatic amine, (0.01 mole) of aniline and (0.005 mole) of 4-amino benzoic acid and 4-Nitro aniline), was added with continuous stirring, and then was refluxed for a period International Journal of Pharmacy and Pharmaceutical Sciences ISSN- 0975-1491 Vol 7, Issue 8, 2015 Innovare Academic Sciences