Plastoquinone analogs: a potential antimicrobial lead structure intensely suppressing Staphylococcus epidermidis and Candida albicans growth

The aim of this study was to evaluate the antimicrobial activity of twenty-five Plastoquinone analogs synthesized previously in a panel of seven bacterial strains (three Gram-positive and four Gram-negative bacteria) and three fungi. PQ1 , which does not contain any substituent(s) on the phenyl ring, was the most potent compound against Staphylococcus epidermidis (8-fold more potent than Cefuroxime, MIC = 1.22 μ g/mL). The antifungal profile of all Plastoquinone analogs indicated that three analogs ( PQ1 , PQ2 , and PQ7 ) displayed the best antifungal activity against Candida albicans , which was about the same activity with the reference standard (MIC = 4.88 μg/mL). The structure-activity relationship study was also carried out to reveal important chemical features. After probing twenty-five Plastoquinone analogs for a potential antimicrobial lead structure, two analogs ( PQ1 and PQ25 ) were selected for further investigation for biofilm evaluation. Based on the tests performed, there was a significant positive correlation between inhibition of the biofilm attachment and time. The results showed that both analogs ( PQ1 and PQ25 ) are able to reduce biofilm mass. Finally, these findings endorse us further efforts to optimize two phenotypes of the Plastoquinone analogs ( PQ1 and PQ25 ) to develop potential antimicrobial drug candidates.