The cell-free medium was used to assess the cytotoxicity against neutrophils as the ratio of the LDH released in total . At 37°C, the neutrophils were equilibrated and incubated for 5 min before treatment with the tested compounds. The treatment lasted for 15 min and the cells were then lysed using Triton X-100 at 25°C for 30 min. The LDH reagent was added and any changes in the absorbance at 492 nm were continuously monitored.