Galacturonic acid

Fresh pumpkin peel was obtained from Laiyang Mengyu Co., Ltd. (Yantai, China). CrCl₃·6H₂O (analytical grade) was obtained by Tianjin Kaitong chemical reagent Co., Ltd. (Shanghai, China). Trifluoroacetic acid (TFA) and insulin were provided by Sigma-Aldrich Co., Ltd. (St. Louis, MO, USA). α-Glucosidase, 4-nitrophenyl-α-D-glucopyranoside (PNPG), penicillin-streptomycin, and albumin bovine were purchased from Beijing Solarbio Technology Co., Ltd. (Beijing, China). Acarbose and monosaccharide standards (rhamnose, arabinose, galactose, glucose, mannose, xylose, fructose, galacturonic acid, and glucuronic acid) were obtained from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Sodium acetate, anhydrous (electrochemical grade), and SS254-500 sodium hydroxide solution were purchased from Thermo Fisher Scientific (Sunnyrale, CA, USA). High-glucose DMEM medium was obtained from Wuhan Servicebio Technology Co., Ltd. (Wuhan, China). Fetal bovine serum was purchased from Zhejiang Tianhang Biotechnology Co., Ltd. (Huzhou, China). Trivalent chromium standard solution was supplied by Beijing Century Aoke Biotechnology Co. Ltd. (Beijing, China). All other chemicals and reagents used were of analytical grade.

Furosine and TFA were purchased from Sigma–Aldrich (San Francisco, CA, USA). Mannose, glucosamine, ribose, glucuronic acid, galacturonic acid, aminogalactose, glucose, and galactose were purchased from Yuan-ye Biotechnology Co., Ltd. (Shanghai, China). The purity of these reagents was ˃99%. A total of 17 amino acid standards, ninhydrin (NIN), and a citric acid buffer solution were purchased from Hitachi Inc. (Hitachi Co., Osaka, Japan). HPLC-grade acetonitrile was purchased from Fisher Scientific (Waltham, MA, USA), and C18 Sep-Pak^® SPE tubes were purchased from Sepax (Sepax technology, Cork, Ireland). Ultrapure water was obtained by using a super-pure water system (Sichuan, China). All other reagents used in this study were of analytical grade and were purchased from Sinopharm Chemical Reagent Co. Ltd. (Beijing, China).

Dried fruiting bodies of T. mongolicum Imai were obtained from Zhangjiakou, Hebei Province, China. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) was purchased from Solarbio Science and Technology Co., Ltd. (Beijing, China). The total antioxidant capacity assay kit for the ABTS method was purchased from Beyotime Co., Ltd. (Shanghai, China). Monosaccharide standards (mannose, ribose, rhamnose, glucuronic acid, galacturonic acid, N-acetyl-D-glucosamine, N-acetyl-D- galactosamine, glucose, galactose, xylose, arabinose, and fucose) were purchased from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). All the reagents and chemicals used in this study were analytical or HPLC grade.

Hemerocallis citrina Borani was obtained from Qingyang, Gansu, China. Standards of glucose, mannose, fucose, rhamnose, xylose, galactose, arabinose, glucuronic acid, ribose, and galacturonic acid were purchased from Shanghai Yuanye Biotechnology (Shanghai, China). Absolute ethanol was purchased from Fuyu Fine Chemical (Tianjin, China). Trifluoroacetic acid, methanol, sodium hydroxide, hydrochloric acid, carbazole, 1-phenyl-3-methyl-5-pyrazolone, 3,5-dinitrosalicylic acid, sulfuric acid, Coomash bright blue, chloroform, potassium bromide, sodium azide, sodium acetate, anthranone, and other reagents were purchased from Solarbio Biotechnology (Beijing, China). ABTS and FRAP assay kits were purchased from Suzhou Keming Biotechnology (Suzhou, China). Distilled water was used in these experiments.

Buddleja officinalis was purchased from the Anhui Bozhou Herb Market (Bozhou, China), which was identified by Prof. Qingping Xiong from Huaiyin Institute of Technology, Huai'an, Jiangsu, China.
Dextrans with different molecular weight (M_w) were from American Polymer Standards Co. (Colorado, USA). Monosaccharide (rhamnose, arabinose, fucose, xylose, mannose, glucose, and galactose) and uronic acid (glucuronic acid and galacturonic acid) standards were obtained from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). The 1-phenyl-3-methyl-5-pyrazolone (PMP) was purchased from Hangzhou Dayangchem Co. Ltd. (Hangzhou, China). DEAE-52 cellulose and SephadexG-100 were purchased from Whatman (Maidstone, Britain) and Amersham (Uppsala, Sweden), respectively. All other reagents used in this study were of analytical grade.