The splenocytes were activated for 24 h in the presence of IL-2. For cytotoxicity assays, cells (effector cells, 5 × 106/mL) were further co-cultured with YAC-1 (target cells, 5 × 105/mL) in the 96-well plates at 37 °C in 5% CO2. Each well was added various concentrations of AHG, or LNT (40 μg/mL, positive control) and medium alone, respectively. After 20 h, the activity of NK cell was determined by MTT assay and calculated by the following formula: NK cell activity (%) = [ODT − (ODS − ODE)]/ODT × 100%, where ODT is optical density value of target cells control, ODS is optical density value of test samples and ODE is optical density value of control effector cells.