Hydroxy Isothiocyanates

antifungal and antibacterial activities at concentrations of 7.8 to 15,6uglml, respectively, and that a possible target of the ITC compounds might be the cellular sulfhydryl group, In recent years, a number of multidrug transporters have been found in various organisms including bacteria and human cells.3) A promising way to conquer such multidrug resistance is to inactivate the eMux protein involved in drug exclusion. In this context, it has been reported that sulfhydryl-reactive reagents inactivate a wide variety of eMux proteins including the EmrE-mediated transporter,`) metaltetracyclinelH' antiporter,5) and qacC-mediated multidrug exporter.6} Moreover, Tanaka et aL reported that hlTC overcomes cisplatin resistance in human head and neck cancer cells.7) Based on these reports, we expected that hlTC, which is a sulfhydryl-blocking reagent, might inactivate transport protein and therefore have a synergetic antimicrobial eflect with some antibietics on IEscherichia coli and Staphylococcus aureus. Antibiotics were all from commercial sources and ITCs including hlTC were synthesized as previously reported.S・9) hlTC was confirmed to be stable in M9 minimal medium (M9) and nutrient broth (NB) with or without antibiotics. When hlTC alone was incubated at 37eC with shaking, 99.9% and 95.5% were recovered after 1 h in M9 and NB, respectively, and 85.1% (in M9) and 71.3% (in NB) remained unchanged even after 24 h. Upon incubation in M9 with antibiotics, hlTC remained almost free, suggesting