Thiolated plastoquinone analogs: Synthesis, characterization, and antimicrobial evaluation

Abstract

New organic compounds containing quinone moiety continue to be developed and used for a broad spectrum of applications as dyes, drugs, herbicides, fungicides, bactericides, plant-growth regulators, analytical reagents, photoresistors, catalysts, and dehydrogenating agents in organic synthesis. Therefore, in this paper, new plastoquinone analogs possessing arylthio side chain at the 2-position and 2- and 3-positions have been synthesized as possible antibacterial and antifungal agents. Besides single crystal X-ray structural characterization of 3d, 3e, and 4e, the structures of all compounds (3a-h and 4a-h) have been determined based on spectral (IR, H-1 NMR, C-13 NMR, and mass) data. The current study also contains in vitro antimicrobial screening (using microbroth dilutions method) of synthesized thiolated plastoquinone analogs. The analog containing dimethyl groups within thio moiety (3d) shows moderate antibacterial activity against E. faecalis compared to that of Amikacin. Additionally, the compounds (3d, 3h, and 4f) possessed the activity against S. aureus. 3d was also able to induce appreciable growth inhibitory activity against C. albicans and C. tropicalis with the MIC value of 78.12 mu g/mL and 19.53 mu g/mL, respectively. This study suggests that four analogs (3d, 3e, 3h, and 4f) could be potential candidates for further development since they show a broad spectrum. (C) 2019 Elsevier B.V. All rights reserved.