Abstract
Antibiotic resistance is a major health problem; therefore, new antibacterial agents will need to be continuously developed. A series of novel bichalcophenes has been tested and found to have antimicrobial activity against selected bacteria. Due to the promising antimicrobial effects of these 4-substituted phenyl bichalcophene derivatives, the study reported here was launched to examine the interaction between novel bichalcophenes and tetracycline. The minimum inhibitory concentration values for all bichalcophenes were between 8 and 64 mu M. Many of the bichalcophenes had synergistic activity that increased the inhibitory effect of tetracycline against bacterial growth, as indicated by the fractional inhibitory concentration index. The post-antibiotic effects of the novel bichalcophenes were determined. Many bichalcophenes were able to elongate the period required for bacteria to recover and grow after a brief exposure to tetracycline. Escherichia coli did not develop resistance to many bichalcophenes over a period of 7 days. A structural activity relationship could be characterized, as monocationic derivatives were more active than the corresponding mononitriles. The presence of a pyridyl group and/or furan ring reduced the activity, while the presence of a phenyl or thiophene ring enhanced the antibacterial activity. Our results suggest that bichalcophenes could be useful to elevate the shelf life of many antibiotics.