The antiproliferative effects of compound 23 on normal cells were investigated by MTT assays comparing it to the STAT3 inhibitor Stattic, which showed growth inhibition activity in both tumor and normal cells, whereas compound 23 exhibited selective inhibitory activity against cancer cells (IC50 14.62 μM for MCF-10A cells and IC50 35.60 μM for L02 cells), indicating a higher selectivity than Stattic. Here, STAT3 is linked to cancer.