Quinic acid

Chromatographically pure acetonitrile and acetic acid was purchased from Thermo Fisher (Waltham, MA, USA). Catechins (C), epicatechin (EC), gallocatechin (GC), epigallocatechin (EGC), epigallocatechin gallate (ECG), gallocatechin gallate (GCG), epigallocatechin-3-O-gallate (EGCG), procyanidin B1, procyanidin C1, kaempferitrin, rutin, isoquercetin, myricetin-3-O-galactoside, myricetin-3-O-rutinoside, galloylglucose, gallic acid, cinnamic acid, chlorogenic acid, shikimic acid, p-coumaric acid, quinic acid, pyrogallic acid, theogallin, strictinin, theanine, theobromine, ethyl gallate, tannic acid, caffeine, L-sodium glutamate, and D-glucose were purchased from Yuanye (Shanghai, China). Quercetin, myricetin, kaempferol, and kaempferol-3-O-glucoside were purchased from Shanghai Zzstandard (Shanghai, China). Amino acid mixture standard reagent, borate buffer solution, o-phthalaldehyde (OPA), and 9-fluorene methyl chloroformate (FMOC) were purchased from Agilent Technology (Santa Clara, CA, USA). n-Hexane was purchased from Thermo Fisher (Waltham, MA, USA). 2-Methyl-3-heptanone and n-alkanes (C₇–C₃₀) were purchased from Sigma (St. Louis, MO, USA).

Standards for high-performance liquid chromatography (HPLC) were purchased from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China) and included glucose, fructose, sucrose, tartaric acid, malic acid, citric acid, and quinic acid. The HPLC-grade reagents methanol and acetonitrile were acquired from Sigma-Aldrich Chemical Co., Ltd. in Shanghai, China. All additional chemicals were purchased from Sinopharm Chemical Reagent Co., Ltd. in Shanghai, China, and were of analytical quality.

Dimeric catechins, such as theaflavin-3ʹ-gallate (TF-3ʹ-G), theaflavin-3,3ʹ-digallate (TF-DG), theaflavin-3-gallate (TF-3-G), theaflavin (TF), procyanidin B2, and procyanidin B1, were sourced from ChemFaces (Wuhan, Hubei, China). Additionally, the following compounds were procured from Sigma (St. Louis, MO, USA): nine flavanols, namely (−)-epigallocatechin (EGC), (−)-epicatechin (EC), (−)-gallocatechin gallate (GCG), (−)-epigallocatechin gallate (EGCG), (+)-catechin (C), (−)-gallocatechin (GC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin-3-(4′'-O-methyl) gallate (EGCG-4′'-O-Me), and (−)-epiafzelechin 3-gallate; fifteen amino acids; eight kaempferol-O-glycosides and quercetin-O-glycosides; as well as flavone-C-glycosides, including vitexin and isovitexin. Other chemicals such as 1-ethyl-5-hydroxy-2-pyrrolidinone, quinic acid, benzyl primeveroside, pyroglutamic acid, pipecolic acid, choline, caffeine, and adenosine monophosphate (AMP), were procured from Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Milli-Q water was used in this study (Millipore, Billerica, MA, USA). Liquid chromatography-mass spectrometry (LC-MS) grade formic acid, methanol, and acetonitrile of were obtained from Merck (Darmstadt, Germany) (Gao et al., 2022 (link), Gao et al., 2022 (link), Peng et al., 2021 (link)).