Phenylalanine

Three bags of Chinese medicine granules were randomly selected and weighed accurately about 200 mg. Methanol:water (8:2, V:V) was added in the ratio of 1:5 (1 g:5 ml), and the mixture was vortex-mixed. Centrifugation was performed at 4°C for 10 min with a centrifugal force of 20,000 × g. The supernatant was filtered with 0.22 um membrane, and the filtrate was taken for analysis. Chemicals of phenylalanine, berberine, ferulic acid, quercetin, and baicalein were purchased from Solarbio (Beijing, China). Arachidonic acid was purchased from Shanghai Yuanye Bio-Technology Co., Ltd (Shanghai, China). Wogonin was purchased from National Institutes for Food and Drug Control (Beijing, China). The details were shown in Table 2.

1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) were purchased from Sigma Chemical Co. (St. Louis, MO, USA). Ferric-tripyridyltriazine (Fe³⁺-TPTZ) is purchased from Beyotime Biotechnology (Shanghai, China). Chromatographic grade analytical standards asparaginic acid, glutamic acid, asparagine, serine, glutamine, histidine, glycine, threonine, citrulline, arginine, alanine, tyrosine, cystine, valine, methionine, tryptophan, phenylalanine, isoleucine, leucine, lysine, hydroxyproline, proline, 5′-CMP, 5′-UMP, 5′-GMP, 5′-IMP, 5′-XMP, 5′-AMP, trehalose, mannitol, quininic acid, l-malic acid and fumaric acid purchased from Solarbio Science & Technology Co., Ltd. (Beijing, China). α-Amylase, α-glucosidase, 4-nitrophenyl α-d-glucopyranoside (PNPG), and soluble starch were purchased from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). All other reagents were analytical grade and obtained from Chengdu Kelong Chemical Factory (Chengdu, China).

BBR, dopamine, and l-dopa were obtained from J&K Scientific Ltd (Beijing, China). 3,4-Dihydroxybenzylamine (as an internal standard, IS) was purchased from Alfa Aesar Chemical Co., Ltd (Ward Hill, MA, USA). Tyrosine, phenylalanine, α-methylphenylalanine, BLMA5 (an inhibitor of TH), and benserazide (an inhibitor of DDC) were obtained from Solarbio Life Science Co., Ltd (Beijing, China). ¹⁵N-Tyrosine (¹⁵N-Tyr, purity > 98%) was obtained from Cambridge Isotope Laboratories, Inc. (MA, USA). Cefadroxil, terramycin, and erythromycin were obtained from Solarbio Life Science Co., Ltd (Beijing, China). Carbidopa was from Selleckchem (Selleck Chemicals, Houston, TX, USA). P and MPTP-HCL were from Medchemexpress (MedChem Express LLC, Princeton, NJ, USA). The purity of the standards above was >98% (HPLC). The TH ELISA kit was from Shanghai Bangyi Biotechnology, Ltd (Shanghai, China). The DDC ELISA kit was from Shuangying Biological, Ltd (Shanghai, China). The PAH ELISA kit and BH₄ ELISA kit were obtained from Shanghai Fusheng, Ltd (Shanghai, China) and Shanghai Jianglai, Ltd (Shanghai, China), respectively. The ROS assay kit was from the Nanjing Jiancheng Bioengineering Institute (Nanjing, China).