Human meningioma cell lines (IOMM-Lee, CH157MN) were obtained from Elmar Kirchesa (Institute of Neuropathology, Otto-von-Guericke-University, Germany) and Jerry Jeff Jaboin (Washington University of Medicine, USA) [22 (link)–25 (link)]. Human neuron culture was purchased from ScienceCell Research Laboratories and maintained under the conditions provided by ScienceCell Research Laboratories. Standard laboratory techniques were used to grow and treat these cells. Drug stock solutions were prepared in dimethyl sulfoxide (DMSO). An equal amount of DMSO (0.01 %) was added to untreated control cells. Dose-response studies were conducted to determine the suitable concentration of the drugs used in the experiments [26 (link), 27 (link)]. Cells were treated with 25 μM Limonin (LKT Laboratories), 25 μM Tangeritin (LKT Laboratories), 25 μM 6-Gingerol (Sigma-Aldrich), 25 μM Zerumbone (LKT Laboratories), 25 μM Ganoderic Acid A (ChromaDex), 25 μM Ganoderic Acid DM (ChemFaces), and 25 μM hydroxyurea (Sigma) for 24 h for induction of apoptosis. After treatments, cells were used for determination of the mechanisms of apoptosis.