Vitexin

Catechin (C, ≥98%), galloCatechin (GC, ≥98%), galloCatechin-3-gallate (GCG, ≥98%), epiCatechin (EC, ≥98%), epiCatechin-3-gallate (ECG, ≥98%), epigalloCatechin (EGC, ≥98%), epigalloCatechin-3-gallate (EGCG, ≥98%), caffeine (CAF, ≥98%), theaflavins (TF, ≥95%), theaflavins-3-gallate (TF3G, ≥98%), theaflavin-3′-gallate (TF3′G, ≥98%), theaflavine-3,3′-digallate (TFDG, ≥98%), quercetin-3-O-galactoside (≥98%), myricetin-3-O-galactoside (≥98%), kaempferol-3-O-rutinoside (≥98%), vitexin (≥98%), astragaloside (≥98%), quercetin (≥98%), and kaempferol (≥98%) were purchased from Shanghai yuanye Bio-Technology Co., Ltd. (Shanghai, China). l-alanine, l-arginine, l-aspartic acid, l-cystine, l-glutamic acid, glycine, l-histidine, l-isoleucine, l-leucine, l-lysine, l-methionine, l-phenylalanine, l-proline, l-serine, l-threonine, l-tyrosine, l-valine, l-asparagine, l-glutamine, theanine, γ-aminobutyric acid, and l-tryptophan were purchased from Sigma (Sigma-Aldrich Co., St. Louis, MO, USA). Anthrone reagent and ninhydrin/formic acid reducing agent were purchased from BeiJing DingGuochangSheng Biotech. Co., Ltd. (Bejing, China). Ethyl caprate (≥99%) was purchased from Shanghai Macklin Biochemical Technology Co., Ltd. (Shanghai, China), and n-alkane mixed standard C7-C40 was purchased from o2si (o2si smart solutions—an LGC Standards Company, Charleston, SC, USA).

HPLC-grade acetonitrile and formic acid were purchased from Thermo Fisher Scientific Company (USA). Ultra-pure water was purchased from Watsons Company (China). All other reagents were of analytical grade.
The reference standards such as kaempferol, isoquercetin, astragalin, rutin, quercetin, baicalein, and palmitic acid were purchased from Herbpurify Co., Ltd. (Chengdu, China); emodin-8-O-β-D-glucoside, quercitrin, vitexin, and vitexin-rhamnoside were purchased from Yuanye Bio-Technology Co., Ltd. (Shanghai, China); isorhamnetin, catechins and epicatechin were purchased from Institutes for Food and Drug control (Beijing, China).
The plant materials of T. hemsleyanums were collected from different provinces in China, as Zhejiang (ZJ1, ZJ2, and ZJ3), Guangxi (GX1, GX2, and GX3), Yunnan (YN1, YN2, and YN3), Fujian (FJ1, FJ2, and FJ3), Guizhou (GZ1, GZ2, and GZ3), and Hubei (HB1, HB2, and HB3). The botanical authentication was performed by Professor Lingchuan Xu from Department of Pharmacognosy, Shandong University of Traditional Chinese Medicine. A voucher specimen (no. TH20171201~TH20181118) was deposited in Key Lab for Natural Product, Shandong Province. The dried rhizome parts of T. hemsleyanums were used for further analysis.

Tartary buckwheat, adzuki bean, walnut, wolfberry and xylitol were kindly provided by Ningxia Huantai Bio-Technology Co., Ltd (Ningxia, China). Standard reagents (gallic acid, rutin, quercetin, myricetin, vitexin and isovitexin), α-glucosidase (100 U) and p-nitrophenyl-a-D-glucopyranoside (pNPG) were purchased from Shanghai Yuanye Bio-Technology Co., Ltd (Shanghai, China). Pepsin (Sigma P7000, from porcine gastric mucosa) and pancreatin enzyme (Sigma P7545, from porcine pancreas) were purchased from Sigma Aldrich Co (St. Louis, MO, United States). The other chemicals and reagents used in this study were of analytical grade.