2.9. LDH Assay

Cell viability, as determined by cell membrane integrity, was assessed by quantifying lactate dehydrogenase (LDH) activity using a commercially available kit (Scheme 1). The manufacturer’s recommendations were followed with minor modifications. Briefly, SH-SY5Y cells were treated with 1:2 serial concentrations of SC derivatives samples (from 0.5 to 6.5 mg/mL) and incubated for 24 and 48 h. Once incubation time was reached, 50 µL of each cell supernatant was transferred to a new plate, mixed with 50 µL of reagent, and incubated in the dark for 20 min at room temperature. The absorbance from the released LDH was quantified at 490 nm wavelength and 650 nm as reference wavelength with the aid of a microplate reader (Thermo Scientific Multiskan™ FC Microplate spectrophotometer). Cells without treatment (DMEM) were the negative control while cells treated with 0.1% Triton X-100 were the positive one.

Percentage cell viability was calculated as follows: