Antimicrobial activities and mode of action of the selected novel thienopyrimidines derivatives 2-[2-(diphenylmethylene) hydrazino]-5-isopropyl--3-methylthieno [2, 3-d] pyrimidin-4-one Abstract Background and purpose: Although thienopyrimidines have an important antimicrobial efficacy, there is still a lack of understanding their antimicrobial mode of action. The current study aims to assess the antimicrobial activity of newly synthesized thienopyrimidines derivatives against some pathogens and

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... to Materials and methods: Newly synthesized thieno[2,3-d]pyrimidinediones compounds examined for antimicrobial activity against pathogenic organisms by cut plug and viable cell counting method. The minimum inhibitory concentration (MIC) of (compound no. 20), it's mode of action; cytotoxicity and LC 50 were determined. Results: One compound, compound no. 20 displayed potent activity. The growth inhibitory effect (M/C) of the compound no. 20 differed among the tested strains. The inhibition becomes stronger; Candida albicans> Escherichia coli> Staphylococcus aureus. The MIC for all the tested microorganisms was > 50 <100 μg/mL. E. coli and C. albicans recorded highest value of potassium flow. Compound no. 20 affects oxygen consumption and exhibited cytotoxicity against E. coli. LC50 value with brine shrimps was estimated at 48.736 μg/mL concentration.