Arylthio analogs of 5,8-quinolinedione: Synthesis, characterization, antibacterial, and antifungal evaluations

Abstract

A set of bis(arylthio) substituted 5,8-quinolinedione derivatives were synthesized and investigated for their in vitro antimicrobial effect. The antibacterial and antifungal activities of 6,7-bis(arylthio)-5,8-quinolinedione (4a–f) and 6,7-bis(arylthio)-2-methyl-5,8-quinolinedione (5a–f) were evaluated against four gram-negative bacteria, three gram-positive bacteria, and three fungi strains. The bis(methoxyarylthio) 5,8-quinolinedione analogs presented better activity against especially gram-positive bacteria compared to bis(halogenarylthio) 5,8-quinolinedione analogs. Bis(3-methoxyarylthio) 5,8-quinolinedione (4e) had the same activity of the reference drug against Staphylococcus aureus. Bis(2-methoxyarylthio) 5,8-quinolinedione (4f) showed two-and-a half-fold better activity with 89.69 μM against Enterococcus faecalis, and two-fold better activity with 11.20 μM against Staphylococcus epidermidis. Bis(2-methoxyarylthio)-2-methyl-5,8-quinolinedione 5f exhibited five-fold higher antibacterial activity with 43.44 μM against E. faecalis and also eight-fold activity of the reference drug with 2.71 μM against S. epidermidis.