P hydroxycinnamic acid

Hyperoside (≥98.0%), quercetin (≥98.0%), astragalin (≥98.0%), kaempferol (≥98.0%), and isorhamnetin (≥98.0%) were supplied from National Institutes for Food and Drug Control (Beijing, China). Luteolin-7-O-glucoside (≥98.0%), isoquercitrin (≥98.0%), 4-caffeoylquinic acid (4-CQA) (≥98.0%), 3-caffeoylquinic acid (3-CQA) (≥98.0%), 4,5-dicaffeoylquinic acid (4,5-DiCQA) (≥98.0%), 3,4-dicaffeoylquinic acid (3,4-DiCQA) (≥98.0%), 3,5-dicaffeoylquinic acid (3,5-DiCQA) (≥98.0%), caffeic acid (CA) (≥98.0%), p-hydroxycinnamic acid (≥98.0%), and 5-O-feruloylquinic acid (5-FQA) (≥98.0%) were purchased from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Their structures (shown in Figure 1) were fully explicated by spectra data (ESI-MS), which followed the methods of Zhang et al. [15 (link)].
Acetonitrile (MS grade) and formic acid (MS grade) were supplied from Thermo Fisher Scientific Inc. All the other chemicals of analytical grade were commercially available from Beijing Chemical Works (Beijing, China). Other reagents were of analytical grade. Deionized water for preparing samples was purified by MilliQ50 SP Reagent Water System (Bedford, MA, USA). Distillated water for mobile phase was purchased from A. S. Watson Group (Hong Kong) Ltd.

Epicatechin, kaempferol, quercetin, rutin, isoquercitrin, syringic acid, p-coumaric acid, chlorogenic acid, cryptochlorogenic acid, caffeic acid, ferulic acid and gallic acid were purchased from Adamas Reagent, Ltd. (Shanghai, China). Other standard reference materials including 4-methoxysalicylic acid, p-hydroxycinnamic acid, isoferulic acid, 1,3-dicaffeoylquinic acid, gentiopicrin, grosvenorine, diosmin, isorhamnetin and baicalein were obtained from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). 2,4,6-tri(pyridin-2-yl)-1,3,5-triazine (TPTZ), 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 4-nitrophenyl α-D-glucopyranoside (p-NPG) were all obtained from Adamas Reagent, Ltd. (Shanghai, China). Acetonitrile and formic acid (99.9%, HPLC grade) were obtained from Thermo Fisher Scientific (Waltham, MA, USA). Cellulase (400 u/mg) from Trichoderma Vride G, hemiCellulase (20,000 u/g) and pectinase (500 u/mg) from Aspergillus niger were all supplied from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). All other reagents and chemicals used in this study are analytical grade.

Five flavonoid reference standards including hyperoside, quercetin, astragalin, kaempferol, and isorhamnetin were purchased from National Institutes for Food and Drug Control (Beijing, China). Two flavonoid reference standards including isoquercitrin and luteolin-7-O-glucoside were purchased from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Eight chlorogenic acid reference standards including 3-caffeoylquinic acid(3-CQA), 4-caffeoylquinic acid(4-CQA), 3,4-dicaffeoylquinic acid (3,4-DiCQA), 3,5-dicaffeoylquinic acid(3,5-DiCQA), 4,5-dicaffeoylquinic acid(4,5-DiCQA), p-hydroxycinnamic acid, caffeic acid(CA) and 5-O-feruloylquinic acid (5-FQA) were purchased from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Their structures (shown in Figure 9) were fully elucidated by spectra data (ESI-MS). The purities of all the standards were no less than 98%. All the standard were resolved in 80% methanol.
Acetonitrile (MS grade) and formic acid (MS grade) were purchased from Thermo Fisher Scientific Inc. Deionized water used throughout the experiment was purified by MilliQ50 SP Reagent Water System (Bedford, MA, USA) for preparing samples.