Abstract
A series of dibenzo[b,e]ox(thi)epin-11(6H)-one O-benzoyloximes has been synthesized and structurally elucidated by means of IR, 1H-NMR, 13C-NMR, MS, and elemental analysis. The newly developed compounds were screened at concentrations of 200–25 μg/mL for their antibacterial activity against Gram+ve organisms such as Methicillin-Resistant Staphylococcus Aureus (MRSA), Gram−ve organisms such as Escherichia coli (E. coli), and at the same concentration range for their antifungal activity against fungal strain Aspergillus niger (A. niger) by the cup plate method. Ofloxacin and ketoconazole (10 μg/mL) were used as reference standards for antibacterial and antifungal activity, respectively. The dibenzo[b,e]oxepines 6a–c and 6e–h showed low antimicrobial activity (MIC 125–200 μg/mL) compared to the reference substances, whereas a major improvement (MIC 50–75 μg/mL) was achieved with the synthesis of the corresponding bromomethyl derivative 6d. Moreover, replacement of oxygen by its bioisosteric sulfur led to isomeric dibenzo[b,e]thi-epine derivatives 6g,h which significantly exhibited higher antimicrobial activity (MIC 25–50 μg/mL) against all tested culture strains used in the present study, demonstrating that a change of chemical class from dibenzo[b,e]oxepine to dibenzo[b,e]thiepine significantly improves the antimicrobial activity. Further variation, such as the oxidation of the thiepine sulfur to the corresponding isomeric dibenzo[b,e]thiepine 5,5-dioxide derivative 9, comparatively failed to exhibit high activity (MIC 200 μg/mL) against S. aureus, E. coli or A. niger.
Highlights
The emergence of the antimicrobials resistance and multiresistance of bacterial and fungal infectious agents has urged the research for new antimicrobial substances and for new strategies for the treatment of infectious diseases which still remain a top public health problem in the world
The aim of this study was to evaluate the in vitro antimicrobial activity of some newly synthesized dibenzo[b,e]oxepin-11(6H)-one oxime derivatives which constitutes the fundamental structure of many products with biological activity including antidepressant [1,2,3,4], antipsychotic [5], antiinflammatory [6, 7], antibacterial and antifungal, and antidepressant activity [8]
Based on the facts that oximes and their derivatives have attracted considerable attention since the past few decades due to their chemotherapeutic value, as they were found to be antihyperglycemic [9], anti-neoplastic [10], anti-inflammatory [11], and antimicrobial [12], and in continuation of our investigations on the class of dibenzo[b,e]oxepines with potential pharmacological properties, the new series of isomeric dibenzo[b,e]oxepin-11(6H)-one O-benzoyloximes and dibenzo[b,e]thiepin-11(6H)-one O-benzoyloximes substituted with a methyl group at 2-position of dibenzo[b,e]ox(thi)epine nucleus has been synthesized and screened for the first time on antimicrobial activity [13]
Summary
The emergence of the antimicrobials resistance and multiresistance of bacterial and fungal infectious agents has urged the research for new antimicrobial substances and for new strategies for the treatment of infectious diseases which still remain a top public health problem in the world. Based on the facts that oximes and their derivatives have attracted considerable attention since the past few decades due to their chemotherapeutic value, as they were found to be antihyperglycemic [9], anti-neoplastic [10], anti-inflammatory [11], and antimicrobial [12], and in continuation of our investigations on the class of dibenzo[b,e]oxepines with potential pharmacological properties, the new series of isomeric dibenzo[b,e]oxepin-11(6H)-one O-benzoyloximes and dibenzo[b,e]thiepin-11(6H)-one O-benzoyloximes substituted with a methyl group at 2-position of dibenzo[b,e]ox(thi)epine nucleus has been synthesized and screened for the first time on antimicrobial activity [13]
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