Design, Synthesis, Characterization and Biological Evaluation of Novel Depsides as Potential Antibacterials

Sixteen depsides were synthesized to screen for their antibacterial activity. All of them were reported for the first time. Their chemical structures were clearly determined by FTIR, 1H NMR, ESI mass spectra. All the compounds were assayed for antibacterial and antifungal activities against two Gram-positive bacterial strains (Bacillus subtilis ATCC 6633) and (Staphylococcus aureus ATCC 29747)and two gram-negative bacterial strains (Escherichia coli ATCC 8739) and (Pseudomonas aeruginosa ATCC 25619) the MIC and zone of inhibition calculated by cup-plate method and serial dilution method and two fungal strains (Aspergillus niger ATCC 90292) and (Candida albicans ATCC 24433)by the micro-broth dilution method.Compound2-(2- propoxy -2-oxoethylphenyl (4-methoxyphenyl)acetate(P6) and 2-(2- propoxy-2-oxoethylphenyl(4-methylphenyl)acetate(P7) showed powerful antibacterial activities against E. coli with MIC of 2.0 40mg/ml while compound 2-(2- propoxy -2-oxoethylphenyl(4-methylphenyl)acetate (P7) and 2-(2- propoxy -2-oxoethylphenyl and (3-methoxyphenyl)acetate (P8) exhibited significant antibacterial activities against B. subtilis with MIC of 3.12 40mg/ml, which were superior to the positive controls amoxycillin trihydrate and ciprofloxacin HCl, respectively and compound 2-(2- propoxy -2-oxoethyl) phenyl 4-methylbenzoate (P8) was found to have highest antifungal activity against Candida albicans ATCC 24433. On the basis of the biological results, quantitative structure activity relationships were discussed. Keywords: Depsides, Antibacterials, Antifungal, Quantitative structure activity relationship.