Then the plates are read with a Spectramax Gemini XS microplate fluorometer (Molecular Devices Corporation, Sunnyvale, CA, USA) using an excitation wavelength of 536 nm and an emission wavelength of 588 nm. From the sigmoidal inhibition curves, the IC 50 values were calculated by linear regression and 4-parameter logistic regression using SoftmaxPro software (Molecular Devices Corporation, Sunnyvale, CA, USA).