Cytotoxicity was also determined using the MTT
method. After 48 h incubation with the test samples,
MTT solution (10 µl, 5 mg/ml in PBS) was added
to the wells and incubated at 37oC for 2 hours. The
medium was removed, and isopropanol containing
0.04 M HCl was then added to dissolve the
formazan production in the cells.