Secoxyloganin

Methanol and formic acid were purchased from Fisher Scientific (Fair Lawn, NJ, USA). Dimethyl sulfoxide (DMSO) was acquired from Meridian Medical Technologies (MREDA, New York, NY, USA). Water for UHPLC/Q-Orbitrap-MS analysis was purified by the Milli-Q water purification system (Millipore, Billerica, MA, USA). QZC samples were provided by Shaanxi Buchang Pharmaceutical Co., Ltd. (Shaanxi, China). Reference compounds were obtained from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China), including gallic acid, protocatechuic acid, neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, loganic acid, corilagin, loganin, isochlorogenic acids A−C, angelol A, columbianetin acetate, osthole, columbianadin, akebia saponin D, 5-hydroxymethyl furfural, 4-hydroxybenzoic acid, caffeic acid, hydroxysafflor yellow A, syringin, ferulic acid, secoxyloganin, ellagic acid, columbianetin, angelol G, and isoimperatorin. Benzoylmesaconine, benzoylaconine, and benzoylhypaconine were obtained from Shanghai Acmec Biochemical Co., Ltd. (Shanghai, China). Kaempferol-3-O-rutinoside was obtained from Chengdu Pufei De Biotech Co., Ltd. (Chengdu, China). The purities of these reference compounds were all determined to be above 98% by UPLC analysis.

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.