Quercitrin

All the standards, reagents, and solvents used through experiments were of analytical grade. Apigenin, diosmetin, hyperoside, rutin, quercitrin, luteolin-7-O-glucoside, Apigenin-7-O-glucoside, p-coumaric acid, caffeic acid, rosmarinic acid, and chlorogenic acid standards were purchased from Extrasynthese (Genay, France), and avicularin from Chromadex (Santa Ana, CA, USA). Acetic acid and acetonitrile were purchased from Sigma-Aldrich GmbH (Buchs, Switzerland), and ethanol from Vilniaus degtine, AB (Vilnius, Lithuania). Potassium persulfate, sodium acetate trihydrate, iron (III) chloride hexahydrate, and 2,4,6-tri(2-pyridyl)-S-triazine (TPTZ), 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical, and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were obtained from Sigma-Aldrich (Steinheim, Germany) and Trolox from Fluka Chemika (Buchs, Switzerland). Folin-Ciocalteu reagent, gallic acid monohydrate, aluminum chloride hexahydrate, sodium carbonate, hexamethylenetetramine, copper chloride, and neocuproine were purchased from Sigma-Aldrich GmbH (Buchs, Switzerland). Deionized water used in HPLC and for the samples preparation produced by the Crystal E high-performance liquid chromatography (HPLC, Adrona SIA, Riga, Latvia) water purification system.

Gallic (3), ellagic (38), protocatechuic (45), neochlorogenic (48), caffeic (49), chlorogenic (50), syringic acids (53), myricitrin (59), isoquercitrin (60), hyperoside (64), kaempferol 3-O-glucoside (67), quercitrin (68), isorhamnetin 3-O-glucoside (72), quercetin (77), myricetin (78), kaempferol (80), (+)-catechin (82), and prunin (87) were obtained from Extrasynthese (Genay, France). All reagents and solvents were of analytical grade.

The methanol, hexane, acetone, petroleum ether, dichloromethane, and hydrochloric acid were of analytical grade and were purchased from Labscan (Dublin, Ireland). The HPLC-grade methanol, HPLC-grade acetonitrile, HPLC–grade ethyl acetate, formic acid, sodium chloride, and potassium hydroxide were obtained from Panreac (Barcelona, Spain). The β-Carotene, all-trans-β-apo-8′-carotenal, α-carotene, phytoene, violaxanthin, lutein, β-cryptoxanthin, and lycopene were purchased from Sigma-Aldrich (Taufkirchen, Germany) and the antheraxanthin from DHI (Hørsholm, Denmark). The lutein epoxide, luteoxanthin, zeinoxanthin, 9-cis-antheraxanthin, 9-cis-violaxanthin, 13-cis-violaxanthin, and 9-cis-lutein were obtained as described elsewhere [23 (link),24 (link),25 (link),26 (link),27 (link)]. The gallic acid, p-hydroxybenzoic acid, syringic acid, caffeic acid, m-coumaric, p-coumaric, chlorogenic acid, ferulic acid, naringin, naringenin, ethyl galate, quercetin, kaempferol, crisin, vanillic acid, and myricetin were purchased from Sigma-Aldrich (Madrid, Spain). The quercitrin was obtained from Extrasynthese (Genay, France). All the aqueous solutions were prepared with purified water in a NANOpure Dlamond^TM system (Barnsted Inc., Dubuque, IO, USA).

Methanol of analytical grade purity was from Lab-Scan (Lisbon, Portugal). The culture media Brain Heart Infusion Agar (BHIA), Mueller Hinton Broth (MHB), Mueller Hinton Agar (MHA), and all the antibiotics were obtained from Oxoid (Hampshire, UK). The saline solution was prepared with NaCl from Merck (Darmstadt, Germany). The dye resazurin and crystal violet were purchased from Sigma-Aldrich (St Louis, Mosby, USA). All the organic solvents were HPLC grade. Ultrapure water from purified system (Isopad Isomantle, Gemini BV, Pr Beatrixlaan 301, 7312 DG Apeldoorn, Netherlands) was used. External standards caffeic acid, catechin, chlorogenic acid, ferulic acid, gallic acid, (-)-epicatechin, naringin, p-hydroxybenzoic acid, quercitrin, and rutin were purchased from Extrasynthese (Lyon Nord, Genay Cedex, France). Dulbecco's Modified Eagle Medium (DMEM), fetal bovine serum (FBS), non-essential amino acids, penicillin, streptomycin, and trypsin–EDTA were obtained from Invitrogen Corporation (Life Technologies, SA, Madrid, Spain).

The following chemicals were used: methylglyoxal (40% in water), 2,2–diphenyl–1–picrylhydrazyl,2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid, trolox, metformin hydrochloride, 98–100% formic acid, methanol (HPLC grade), acetonitrile (HPLC gradient grade and LC–MS grade), and water (LC–MS grade) were purchased from Merck–Sigma–Aldrich (Sigma–Aldrich Sp. z o.o., Poznań, Poland); NaCl, KCl, Na₂HPO₄ and KH₂PO₄ (reagent grade) were obtained from Chempur (Piekary Śląskie, Poland); quercetin, quercitrin, astragalin, hyperoside, rutin, nicotiflorin, narcissin, taxifolin, gallic acid, p-coumaric acid, ferulic acid, caffeic acid, and chlorogenic acid were from Extrasynthese (Genay Cedex, France); galegine sulfate was purchased from SelectLab (Münster, Germany). Water was glass-distilled and deionized.
The stock solutions of standards (1 mg/mL) were prepared by dissolving 5 mg of a reference compound in 5 mL of methanol. Working standard solutions in the range of 10–400 μg/mL were made by mixing with 50% aq. (aqueous) methanol (v/v), filtered through hydrophilic Millex Syringe Filters (Durapore 0.22 μm; Millipore, Burlington, MA, USA) and stored at −20 °C.

MEM with Earle's salts, DMEM, fetal bovine serum (FBS), trypsin‐EDTA, and antibiotics were purchased from Biochrom GmbH (Berlin, Germany). Entero‐STIM Intestinal Epithelium Differentiation Medium and MITO+ Serum Extender were purchased from Corning (Wiesbaden, Germany). Hesperetin, peltatoside, hyperoside, kaempferol, ellagic acid, isoquercitrin, quercitrin, phloretin, (−)‐epicatechin, epigallocatechin, epicatechin gallate, procyanidin B1, procyanidin B2, epigallocatechin gallate, gallocatechin, and morine were obtained from Extrasynthese (Genay Cedex, France). Phloridzin, chlorogenic acid, caffeic acid, quercetin, (+)‐catechin, gallic acid, 2‐mercaptoethanol, NaCl, MgSO₄, KCl, CaCl₂, HEPES, and xylitol were purchased from Sigma‐Aldrich (Schnelldorf, Germany). Guaijaverin and avicularin were obtained from Glentham Life Sciences (Corsham, United Kingdom). Purified and concentrated GLE (cGLE) was provided by Belan GmbH (Wels, Austria).30 Guava fruit puree for preparation of fruit extracts was obtained from Tradework BV (Rotterdam, The Netherlands), commercially available GLE and apple extract (AE) were purchased from Pfannenschmidt (Hamburg, Germany). Transwell inserts (12 mm, collagen‐treated, 0.4 μm pore size) and 12‐well plates were obtained from Corning (Wiesbaden, Germany).

Methanol and ethanol were from VWR (Darmstadt, Germany) and were like all other solvents used of HPLC grade. Trolox, 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), Folin-Ciocalteu reagent, quercetin, (−)-epicatechin, procyanidin B1, procyanidin B2, procyanidin C1, p-coumaric acid, trans-cinnamic acid and phloridzin dihydrate were from Sigma–Aldrich (Taufkirchen, Germany). Gallic acid, (+)-catechin, chlorogenic acid, ferulic acid, coffeic acid, rutin trihydrate and acetic acid were purchased from Carl Roth (Karlsruhe, Germany). Avicularin was used from Phytolab (Vestenbergsgreuth, Germany). Protocatechuic acid, hyperoside, isoquercitrin, quercitrin and procyanidin A2 were from Extrasynthese (Genay, France). Reynoutrin was purchased from Carbosynth Limited (Berkshire, UK). 2,2′-Azobis(2-amidinopropane) dihydrochloride (AAPH) was from Fisher Scientific (Nidderau, Germany). HPLC grade water (18 MΩ) was prepared using a MicroPure purification system (Thermo Electron LED GmbH, Niederelbert, Germany). Sodium hydroxide, hydrochloric acid (Merck, Darmstadt, Germany), meta-phosphoric acid (Sigma–Aldrich) and all other chemicals were of analytical grade.