Glutamic acid

Leaves from the Ziziphus jujuba Mill. cv. Dongzao were used, and the picking standard is two leaves and one bud on the fruit-bearing shoot (Figure 1C). The leaves were collected in June 2022 in Baoding (115° 47’E; 38° 87’N) (Hebei Province, China). Liquid chromatography grade solvents methanol and acetonitrile were purchased from Fisher Chemical, 2-propanol from Merck, formal acid from CNW, and 2-Chloro-L-phenylAlanine (≥98%) from Adamas-beta. Alanine, arginine, asparagine, aspartic acid, cystine, glutamine, glutamic acid, glycine, histidine, isoleucine, L-cysteine, leucine, L-hydroxyproline, L-tryptophan, lysine, methionine, phenylAlanine, proline, serine, threonine, tyrosine, valine, and 1,3-dichlorobenzene were all analytically pure and purchased from Beijing Solarbio Science&Technology Co., Ltd.

Cortical neuron cultures were prepared from female SD rats at 17 d of gestation. The pregnant rats were anesthetized then killed by cervical dislocation. The rats were sprayed with 70% ethanol and embryos were removed then quickly decapitated. The cortices were placed in ice-cold plating medium (neurobasal medium (21,103,049, Gibco, USA), 0.5% FBS (16,140,071, Gibco, USA), 2% B-27 supplement (17,504,044, Gibco, USA), 25 mM glutamic acid (IG0710, Solarbio, China), and 0.5 mM L-GlutaMAX (35,050,061, Gibco, USA)) following the removal of the meninges. The cortical neurons were plated on petri dishes coated with poly-D-lysine (P6407, Sigma, USA) and suspended in plating medium. Half of the plating medium was removed and replaced with maintenance medium (neurobasal medium, 0.5 mM L-GlutaMAX, and 2% B-27 supplement) in the same manner every 3 d. The cultured neurons were used in the experiments after 12 d.

Cardamonin (no 110763, purity >99%; National Institutes for Food and Drug Control, Beijing, China), rapamycin (Sigma-Aldrich Co., St Louis, MO, USA), MHY1485 (HY-B0795; MedChemExpress, Monmouth Junction, NJ, USA), AZD0364 (S8708; Seleck Chemicals, Houston, TX, USA), N-Acetyl-L-cysteine (S26121; Yuanye Biological Co., Shanghai, China), and glutamic acid (SG8540-200; Solarbio Co., Beijing, China) were dissolved in dimethyl sulfoxide (DMSO; Sigma-Aldrich Co., St Louis, MO, USA) and stored at 4 °C. CCK8 kit was purchased from Wabcan Co. and Reactive Oxygen Species Assay Kit was purchased from Beyotime Institute of Biotechnology (Jiangsu, China). Antibodies against mTOR, p-mTOR (Ser2481), Raptor, p-p44/42 MAPK (ERK1/2), p44/42 MAPK (ERK1/2), S6K1, p-S6K1 (Thr389), β-actin and the secondary antibodies were purchased from Cell Signaling Technology (Danvers, MA, USA).