Powerful Antibacterial Activity of Phenyl-Thiolatobismuth(III) Complexes Derived from Oxadiazolethiones

摘要

Seven novel 5-substituted phenylthiazole oxadiazolethiones: [Me-PTOT(H)], [MeO-PTOT(H)], [MeS-PTOT(H)], [F-PTOT(H)], [Cl-PTOT(H)], [Br-PTOT(H)], and [CF3-PTOT(H)], {where X-PTOT(H) = 5-[2-(4-X)thiazol-4-yl]-1,3,4-oxadiazole-2(3H)-thione, 4-X = C6H4}, were synthesised from their corresponding thioamides. From these seven heteroleptic thiolatobismuth complexes: BiPh(Me-PTOT)(2) 6, BiPh(MeO-PTOT)(2) 7, BiPh(MeS-PTOT)(2) 8, BiPh(F-PTOT)(2) 9, BiPh(Cl-PTOT)(2) 10, BiPh(Br-PTOT)(2) 11 and BiPh(CF3-PTOT)(2) 12 were synthesised and characterised. Complexes [10(DMSO)(2)] and [11(DMSO)(2)] were structurally characterised using X-ray diffraction. Evaluation of the antibacterial properties of the thiones and their Bi-III complexes against Mycobacterium smegmatis, Staphylococcus aureus (S. aureus), Methicillin-resistant Staphylococcus aureus (MRSA), Vancomycin-resistant Enterococcus (VRE), Enterococcus faecalis (E. faecalis) and Escherichia coli (E. coli) showed that all bismuth(III) complexes were highly effective against all the bacteria, as demonstrated by very low MIC values (1.1-2.1 M). Complexes BiPh(Me-PTOT)(2) 6, BiPh(Cl-PTOT)(2) 10 and BiPh(Br-PTOT)(2) 11, showed best activity against the multi-drug resistant bacteria VRE and MRSA with an MIC value of 1.0 M. All these complexes and their corresponding thiones failed to show any prominent activity against M. smegmatis and E. coli, even at high concentrations. These complexes showed little or no toxicity towards mammalian COS-7 cells at 20 g/mL.