were added, followed by further incubation at 37 °C for 30 min. Fluorescence was measured with an excitation wavelength of 355 nm and an emission wavelength of 460 nm using a FLUOstar OPTIMA microplate reader (BMG Labtech). All compounds were evaluated in duplicates in at least two independent experiments. The determination of IC50 values was conducted analogously. Here, a fourfold dilution sequence (in triplicates) was prepared in assay buffer.