Taxifolin

Semen Hoveniae used in the experiments were obtained in the city of Nanyang, Henan, China. Ethanol (purity ˃ 95%), aceti cacid (purity ˃ 98%), mEthanol (purity ˃ 98%), phenol (purity ˃ 98%) and acetonitrile (purity ˃ 98%) were provided by Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Dihydromyricetin (purity ˃ 98%), taxifolin (purity ˃ 98%), myricetin (purity ˃ 98%), quercetin (purity ˃ 98%), were provided by Shanghai Yuanye Bio-Technology. Co., Ltd. (Shanghai, China). Dimethyl sulfoxide (purity ˃ 98%) was provided by Solarbio (Beijing, China). Pepsin, trypsin and bile salts were provided by Sigma (Saint Louis, MO, USA).

Human serum albumin (HSA) (96–99%, fraction V) and bovine serum albumin (BSA) (96%, fraction V) were purchased from GIBCO Co. (Shanghai, China). 3,5-dinitrosalicylic acid (DNS), potassium sodium tartrate tetrahydrate, soluble starch and 1,1-Diphenyl-2-picrylhydrazyl (DPPH) were acquired from Sigma-Aldrich Chemicals (St. Louis, MO, USA). Isorhamnetin (>98.0%), Apigenin (>98.0%), Naringenin (>98.0%), Kaempferol (>98.0%), Quercetin (>98.0%), Taxifolin (>98.0%), Luteolin (>96.0%), Isoquercitrin (>98.0%), Hyperoside (>98.0%), Astragalin (>98.0%), and Rutin (>98.0%) were purchased from Yuanye Biotechnology Co. (Shanghai, China). Ultrapure water (18.2 MΩ cm resistivity) was obtained from an ELGA water purification system (ELGA Berkefeld, Veolia, Germany). All of other chemicals were analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).

HPLC-grade acetonitrile and methanol were obtained from Fisher (Fair Lawn, NJ, USA), and formic acid was obtained from ACS (Wilmington, DE, USA). Experimental water was purchased from Watsons Trademark Co., Ltd. (Hong Kong, China). The reference standards of protocatechuic acid (CAS: 99-50-3), caffeic acid (CAS: 331-39-5), gallic acid (CAS: 149-91-7), quercetin (CAS: 117-39-5), taxifolin (CAS: 480-18-2), chlorogenic acid (CAS: 27-97-9), astragaloside (CAS: 480-10-4), isoquercetin (CAS: 21637-25-2), rutin (CAS: 153-18-4) and sangone G (CAS: 75629-19-5) were provided by Shanghai Yuanye Bio-technology Co., Ltd. (Shanghai, China). The standard mixture N-ketone C4-C9 for calculating the retention index (RI) of HS-GC-IMS was purchased from Sinopharm Chemical Co., Ltd. (Shanghai, China), and the normal alkane C8-C20 of GC-MS was purchased from Sigma Aldrich Chemical Co., Ltd. (St. Louis, MO, USA).

The reference substances taxifolin and quercetin, with purity above 98%, were obtained from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China), and diosmin, with purity above 99%, was purchased from Ziyi Chemical Reagent Factory (Shanghai, China); chromatographic grade acetonitrile and phosphoric acid were obtained from Thermo Fisher Scientific (Shanghai, China). A 0.45 µm filtration was needed for the standards, flavonoid extract samples and eluent, and some samples were diluted to appropriate concentrations by pure water before HPLC analysis.
Leaves and bark of A. nephrolepis were provided by the Liangshui Experimental Forest Farm (Northeast Forestry University, Yichun, Heilongjiang, China) and collected from one tree of ten years of growth in September 2017. The leaves and bark of A. nephrolepis specimens were certified by Prof Huiyan Gu (Northeast Forestry University, Harbin, China). The materials were dried at ambient temperature for 2 weeks, ground into a homogeneous powder, and then sieved (60–80 mesh). The sieved samples were stored in polyethylene zipper bags at 4 °C until use. The same batch of sample was used in all experiments.

Folin-Ciocalteu’s phenol reagent (F9252, 2N), 2,4,6-tris (2-pyridyl)-s-triazine (TPTZ, ≥ 99%), 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS, ≥ 99%), 2,2-diphenyl-1-picrylhydrazyl (DPPH, D9132), Trolox (≥ 97%), hippuryl-histidyl-leucine (HHL, ≥ 98%), Saccharomyces cerevisiae α-glucosidase (G0660, 28 units/mg solid), type VI-B porcine pancreatic α-amylase (A3176, 14 units/mg solid), and rabbit lung angiotensin-converting enzyme (A6778, ≥ 2.0 units/mg protein) were purchased from Sigma-Aldrich (St. Louis, MO, United States). Analytical standards (greater than 98%) of hydroxytyrosol, esculin, corosolic acid, ursolic acid, maslinic acid, oleanolic acid, taxifolin, luteolin, quercetin, kaempferol, apigenin, chlorogenic acid, plantamajoside, rutin, eriodictyol, tiliroside, apigenin-7-O-neohesperidoside, luteolin-7-O-glucoside, oleuropein, secoxyloganin, and gallic acid were purchased from Yuanye Bio-Technology Co., Ltd., (Shanghai, China). For chromatographic analysis, high-performance liquid chromatography (HPLC)-grade formic acid, acetic acid, and acetonitrile were obtained from Alfa Aesar (Shanghai, China) and Merck (Darmstadt, Germany). Ultrapure water was obtained from a Milli-Q system (Millipore, Bedford, MA, United States).

All chemicals and reagents used in this study were of analytical grade unless stated otherwise. Trolox, gallic acid, Folin–Ciocalteu phenol reagent, 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and 2,4,6-tris (2-pyridyl)-s-triazine (TPTZ) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Standard compounds such as hydroxytyrosol, esculin, taxifolin, luteolin, quercetin, kaempferol, apigenin, chlorogenic acid, plantamajoside, rutin, eriodictyol, tiliroside, apigenin-7-O-neohesperidoside, apigenin-7-O-glucoside, luteolin-7-O-glucoside, oleuropein, secoxyloganin, asiatic acid, oleanonic acid, maslinic acid, corosolic acid, oleanolic acid, and ursolic acid were purchased from Yuanye Bio-Technology Co., Ltd. (Shanghai, China). For chromatography analysis, HPLC-grade acetonitrile and acetic acid were purchased from Merck (Darmstadt, Germany) and Alfa Aesar (Shanghai, China), respectively. Ultrapure water supplied by a Milli-Q system (Millipore, Bedford, MA, USA) was used throughout the experiments.