Grivicich I, Ferraz A, Faria DH, Regner A, Schwartsmann G, Henriques AT, von Poser GL, da Rocha AB. Synergistic effect of three benzopyrans isolated from Hypericum polyanthemum in U-373 MG glioblastoma cell line. Phytother Res. 2008 Dec;22(12):1577ā80. doi: 10.1002/ptr.2490. PMID: 19003947.