This study investigated the effect of the ethyl acetate fraction from O. japonicus extract (OJE) on the growth inhibition of OVCAR‐3 human ovarian cancer cells demonstrated to inhibit cell growth and arrest the cell cycle in OVCAR‐3 cells by blocking the sub‐G1 phase and decreasing cyclin E1/CDK2 expression. The gene discussed is CCNE1; the disease is ovarian cancer.