Apigenin

The chemical reference substances of naringenin and hesperetin were obtained from Sigma-Aldrich (St. Louis, MO, USA). naringenin-7-O-glucuronide and naringenin-4′-O-glucuronide was acquired from Cayman Chemical Company (Ann Arbor, MI, USA). hesperetin-7-O-glucuronide, hesperetin-3′-O-glucuronide, and hesperetin-7-O-sulfate were purchased from Toronto Research Chemicals Inc. (Toronto, ON, Canada). Apigenin was supplied by Shanghai Macklin Biochemical Co., Ltd. (Shanghai, China). Eriodictyol was obtained from Dalian Meilunbio Biochemical Co., Ltd. (Dalian, China). Homoeriodictyol was purchased from Extrasynthese Chemical Company (Genay, France). The internal standard (IS) isoquercitrin was obtained from National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China).
Methanol of LC-MS grade was acquired from Fisher Scientific Inc (Fair Lawn, NJ, USA), and acetonitrile of HPLC grade was purchased from Honeywell B&J Chemicals Inc (Morris Plains, NJ, USA). Water was purified by the Milli-Q system (Millipore Corporation; Billerica, MA, USA). Naringin powder for intragastric administration in animals was extracted from Citrus grandis ‘Tomentosa’, whose purity was 98.8% determined by HPLC [16 (link)].

The standard substances of naringin (purity: 95.0%), naringenin (purity: 95.0%), hesperetin (purity: 95.0%), and p-coumaric acid (purity: 98.0%) were acquired from Sigma-Aldrich (St. Louis, MI, USA). Rhoifolin (purity: 98.0%) and eriodictyol (purity: 98.0%) were acquired from Meilunbio (Dalian, China). Neoeriocitrin (purity: 99.0%) was obtained from Cayman (Ann Arbor, MI, USA). Neohesperidin (purity: 99.0%) and apigenin (purity: 99.0%) were purchased from Macklin (Shanghai, China). Caffeic acid (purity: 99.7%) and isoquercitrin (purity: 97.2%) were purchased from National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China). BL agar medium base was obtained from G-CLONE (Beijing, China) and is composed of dipotassium hydrogen phosphate, sodium chloride, potassium dihydrogen phosphate, ammonium sulfate, calcium chloride, magnesium sulfate, resazurin, L-cysteine, L-ascorbic acid, sodium carbonate, beef meal, peptone, and agar.
LC-MS-grade methanol was acquired from Fisher Scientific (Fair Lawn, NJ, USA). HPLC-grade acetonitrile was purchased from Honeywell B&J Chemicals (Morristown, NJ, USA). LC-MS-grade formic acid was acquired from Sigma-Aldrich (St. Louis, MI, USA). Water was purified with a Milli-Q system (Millipore Corporation; Billerica, MA, USA) and further filtered through a microfiltration membrane (0.22 μm) before use.

Chlorogenic acid, hyperin, rutin, apigenin, quercetin, scopoletin, chrysoeriol, caffeic acid, protocatechin, isorhamnetin, taxifolin, and gentisic acid were purchased from Macklin (Shanghai, China). Methyl alcohol, formic acid, and n-Hexane were purchased from Merck Millipore. The sucrose and stearic acid were purchased from Sigma (St. Louis, MO, USA). Na₂HPO₄, KH₂PO₄, KPO₄, NaCl, CaCl₂, MgSO₄, and NH₄Cl were purchased from Beijing Lanyi Chemical Products Co. Ltd. (Beijing, China). sucrose, stearic acid, agar, peptone, cholesterol, and DMSO were purchased from Lablead (Beijing, China).