A new ionone glycoside, frehmaglutoside I (1), and three new rhemaneolignans A–C (2–4) were isolated from the 95% EtOH extract of the roots of Rehmannia glutinosa. Their structures were determined by extensive spectroscopic (UV, IR, HR-ESI-MS, 1D and 2D NMR) analyses. In addition, these compounds were evaluated for their protective effects on cardiocytes impaired by doxorubicin in H9c2 cells. Among them, compounds 1–3 exhibited protective effects against DOX-induced cardiotoxicity.