2.5. Cell Viability (MTT Assay)

Cell viability MTT assay was carried out according to Alqahtani et al. [24]. In brief, A549 (lung), MCF-7 (breast), and HepG2 (liver) cancer cells were harvested, counted, and plated on the bottom of a 24-well plate (5 x  10⁴ cells/well) for 24 h to allow for attachment. Various concentrations of S. glaucus fractions were added to each well and incubated with the cells at 37°C in the presence of 5% CO₂. After 48 h, 0.1 ml of 5 mg/ml MTT was added to each well, and the plates were again incubated at 37°C and 5% CO₂ for 2–4 hours. Next, the media were aspirated, a solution of 0.01 N HCl in isopropanol was added to each well, and the plates were placed in a shaker for 10 min to dissolve the formed formazan crystals. The absorbance was read at 570 nm using a microplate reader. The concentration at which cell viability is reduced by 50% (IC₅₀) was calculated using OriginPro 8.5 software.