Quantitative Assay of Photoinduced Antibiotic Activities of Naturally-Occurring 2,2′:5′,2″-Terthiophenes

Nine naturally-occurring 2,2':5',2"-terthiophenes were quantitatively evaluated for their in vitro photoinduced growth inhibitory activity against three bacterial strains. All the compounds proved active towards Staphylococcus aureus. As regards Escherichia coli, the unsubstituted 2,2':5'2"-terthiophene (MIC = 0.62 microgram/ml at 4j/cm2 fluence), was found to be the only compound active. None of the compounds tested displayed activity on Pseudomonas aeruginosa at the highest concentration tested.