2.2. Lactate dehydrogenase (LDH) release assay

PBMC were placed in a 96-well plate containing the growth medium and exposed to different concentrations (3.125, 6.25, 12.5, 25, 50, and 100 mg/L) of APM for 48 h. After the incubation period, LDH assay was carried out using a commercial kit (CytoSelectTM LDH Cytotoxicity Assay kit) according to the provider’s instructions. Briefly, 90 µL of the supernatant from each well was mixed with 10 μL of LDH reagent and incubated at 37 °C for 30 min. The optical density was determined at 450 nm using a spectrophotometer (Synergy-HT; BioTek Winooski, VT, USA). Triton X-100-treated cells were used as positive control and the cells without any treatment were used as a negative control.