Isoforsythiaside (IFY) resisted apoptosis in HT22 cells induced by L-glutamate (L-Glu). (A) IFY improved the cell viability of HT22 cells exposed to L-Glu. Simultaneously, IFY showed no toxicity cultured with HT22 cells alone (n = 6). (B) IFY prevented L-Glu-induced HT22 cell apoptosis (n = 6). (C) IFY relieved the mitochondrial membrane potential (MMP) imbalance in L-Glu-damaged HT22 cells (n = 6). (D) IFY ameliorated the overaccumulation of reactive oxygen species (ROS) in HT22 cells damaged by L-Glu (magnification × 20, scale bar: 50 μm (n = 6)). IFY reduced the expression of (E) caspase-3 (n = 6), (F) caspase-8 (n = 6) and (G) caspase-9 (n = 6) in HT22 cells exposed to L-Glu. Data are shown as the mean ± standard error (SEM). # p < 0.05, ### p < 0.001 vs. CTRL, * p < 0.05, ** p < 0.01, *** p < 0.001 vs. L-Glu-exposed HT22 cells.