A series of simple heterocyclic chalcone analogues have been synthesized by Claisen Schmidt conde... more A series of simple heterocyclic chalcone analogues have been synthesized by Claisen Schmidt condensation reactions between substituted benzaldehydes and heteroaryl methyl ketones and evaluated for their antibacterial activity. The structures of the synthesized chalcones were established by IR and ¹H-NMR analysis. The biological data shows that compounds p₅, f₆ and t₅ had strong activities against both susceptible and resistant Staphylococcus aureus strains, but not activity against a vancomycin and methicillin resistant Staphylococcus aureus isolated from a human sample. The structure and activity relationships confirmed that compounds f₅, f₆ and t₅ are potential candidates for future drug discovery and development.
A total of 30 chalcone analogues was synthesized via a base catalyzed Claisen Schmidt condensatio... more A total of 30 chalcone analogues was synthesized via a base catalyzed Claisen Schmidt condensation and screened for their in vitro antibacterial activity against Methicillin-sensitive Staphylococcus aureus (MSSA) and Methicillin-resistant Staphylococcus aureus (MRSA) alone or in combination with non beta-lactam antibiotics namely ciprofloxacin, chloramphenicol, erythromycin, vancomycin, doxycycline and gentamicin. In the checkerboard technique, fractional inhibitory concentration indices (FICI) show that the following combinations like ciprofloxacin with 25 (4'-bromo-2-hydroxychalcone); doxycycline with 21 (4-hydroxychalcone); doxycycline with 25; and doxycycline with 4 (2',2-dihydroxychalcone) were synergistic against MRSA. In term SAR study, the relationship between chalcone structure and their antibacterial activity against S. aureus and synergy with tested antibiotics were discussed. Possible mechanisms for antibacterial activity of chalcones alone as well as the synergistic effect in combinations were proposed by molecular modeling studies, respectively. Combinations of chalcones with conventional antibiotics could be an effective alternative in the treatment of infection caused by MRSA.
N-alkylation of azaphenothiazines using dibromoalkanes or dibromoalkenes did not result in the fo... more N-alkylation of azaphenothiazines using dibromoalkanes or dibromoalkenes did not result in the formation of bis-azaphenothiazines under known conditions such as refluxing, for more than 100 h, with NaNH2/xylene or NaH/toluene. However, when the same reaction was tried with NaH/DMF at −5 °C to r.t., it yielded the desired product in 68–71 % yield. These novel bis-azaphenothiazines containing a suitable alkyl or alkenyl spacer were found to possess moderate to significant antimicrobial activities against three gram positive bacteria (Staphylococcus aureus, Bacillus subtilis, and Staphylococcus epidermis), four gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumoniae) as well as four fungi (Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, and Candida albicans). Compounds 2b–d were found to exhibit strong antifungal activity, comparable to the standard drug miconazole against A. niger and A. fumigatus.
A series of simple heterocyclic chalcone analogues have been synthesized by Claisen Schmidt conde... more A series of simple heterocyclic chalcone analogues have been synthesized by Claisen Schmidt condensation reactions between substituted benzaldehydes and heteroaryl methyl ketones and evaluated for their antibacterial activity. The structures of the synthesized chalcones were established by IR and ¹H-NMR analysis. The biological data shows that compounds p₅, f₆ and t₅ had strong activities against both susceptible and resistant Staphylococcus aureus strains, but not activity against a vancomycin and methicillin resistant Staphylococcus aureus isolated from a human sample. The structure and activity relationships confirmed that compounds f₅, f₆ and t₅ are potential candidates for future drug discovery and development.
A total of 30 chalcone analogues was synthesized via a base catalyzed Claisen Schmidt condensatio... more A total of 30 chalcone analogues was synthesized via a base catalyzed Claisen Schmidt condensation and screened for their in vitro antibacterial activity against Methicillin-sensitive Staphylococcus aureus (MSSA) and Methicillin-resistant Staphylococcus aureus (MRSA) alone or in combination with non beta-lactam antibiotics namely ciprofloxacin, chloramphenicol, erythromycin, vancomycin, doxycycline and gentamicin. In the checkerboard technique, fractional inhibitory concentration indices (FICI) show that the following combinations like ciprofloxacin with 25 (4'-bromo-2-hydroxychalcone); doxycycline with 21 (4-hydroxychalcone); doxycycline with 25; and doxycycline with 4 (2',2-dihydroxychalcone) were synergistic against MRSA. In term SAR study, the relationship between chalcone structure and their antibacterial activity against S. aureus and synergy with tested antibiotics were discussed. Possible mechanisms for antibacterial activity of chalcones alone as well as the synergistic effect in combinations were proposed by molecular modeling studies, respectively. Combinations of chalcones with conventional antibiotics could be an effective alternative in the treatment of infection caused by MRSA.
N-alkylation of azaphenothiazines using dibromoalkanes or dibromoalkenes did not result in the fo... more N-alkylation of azaphenothiazines using dibromoalkanes or dibromoalkenes did not result in the formation of bis-azaphenothiazines under known conditions such as refluxing, for more than 100 h, with NaNH2/xylene or NaH/toluene. However, when the same reaction was tried with NaH/DMF at −5 °C to r.t., it yielded the desired product in 68–71 % yield. These novel bis-azaphenothiazines containing a suitable alkyl or alkenyl spacer were found to possess moderate to significant antimicrobial activities against three gram positive bacteria (Staphylococcus aureus, Bacillus subtilis, and Staphylococcus epidermis), four gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumoniae) as well as four fungi (Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, and Candida albicans). Compounds 2b–d were found to exhibit strong antifungal activity, comparable to the standard drug miconazole against A. niger and A. fumigatus.
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