Epigallocatechin gallate (egcg)

Wine alcohol 65% v/v was obtained from winery Ouro Verde-Miolo Wine Group (Casa Nova, BA, Brazil). Folin-Ciocalteu reagent, ethanol, potassium persulfate, phosphoric acid, and potassium phosphate monobasic were purchased from Merck (Darmstadt, Germany). Trolox (6-hydroxy-2,5,7,8-tetramethylchromate-2-carboxylic acid) and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and 2,2-azino-bis (3-ethylbenzthiazoline-6 sulfonic acid) (ABTS) were supplied by Sigma-Aldrich (St. Louis, MO, USA). Methanol was from J.T. Baker (Phillipsburg, NJ, USA). Ultrapure water was obtained with a Marte Científica purification system (São Paulo, SP, Brazil). External standards of gallic acid, syringic acid, benzoic acid, p-coumaric acid, o-coumaric acid, cinnamic acid, procyanidin B₁, catechin, procyanidin B₂, and caffeic acid came from Sigma-Aldrich (St. Louis, MO, USA). Epigallocatechin gallate, epicatechin, epicatechin gallate, procyanidin A₂, quercetin 3-glucoside, rutin, kaempferol 3-glucoside, myricetin, and isorhamnetin 3-glucoside, quercetin-3-O-glucopyranoside came from Extrasynthese (Genay, France). The trans-Resveratrol was obtained from Cayman Chemical Company (Michigan, EUA, Ann Arbor, MI, USA).

1,10-Phenantroline, (-)-epicatechin, Thiamine, Flufenamic acid, Vanillic acid and Protocatechuic acid were purchased from Sigma (Barcelona, Spain). Procyanidin B2 gallate, Epigallocatechin gallate (EGCG) and epicatechin gallate were purchased from Extrasynthese (Genay, France) and Procyanidin B2 was purchased from Adooq-Bioscience (Irvine, CA, USA).
We used Krebs–Ringer bicarbonate (KRB) buffer (Hepes 11.5 mM, CaCl₂ 2.6 mM, MgCl₂ 1.2 mM, KCl 5.5 mM, NaCl 138 mM, NaHCO₃ 4.2 mM, NaH₂PO₄ 1.2 mM) pH 7.4, supplemented with either 10 mM D-Glucose (KRB-D-Glucose buffer) or 10 mM D-Mannitol (KRB-D-Mannitol buffer). For enterohormone secretion studies, KRB-D-Glucose was supplemented with protease inhibitors: 10 µM amastatin (Enzo Life Sciences, Madrid, Spain), 100 KIU aprotinin (Sigma, Barcelona, Spain) and 0.1% fatty acid free-bovine serum albumin.

All chemicals were at least of analytical grade. Acetic acid, formic acid, hydrochloric acid (37%), toluene, 1-propanol, and 4-dimethylaminocinnamaldehyde (DMACA) were from Merck (Darmstadt, Germany). Acetone, ethanol as well as HPLC grade acetonitrile and methanol were purchased from Sigma-Aldrich (St. Louis, MO, USA). LC–MS grade acetonitrile and methanol used for MS analyses were from Fluka (Buchs, Switzerland). MilliQ 18.2 MΩ water (Millipore, Bedford, MA, USA) was also used.
Standard of (−)-epicatechin was obtained from Sigma-Aldrich and (+)-catechin from Carl Roth (Karlsruhe, Germany). Standards of procyanidin B1, procyanidin B2, procyanidin B3, procyanidin C1, (−)-catechin gallate, (−)-gallocatechin, (−)-gallocatechin gallate, (−)-epicatechin gallate, (−)-epigallocatechin and (−)-epigallocatechin gallate were obtained from Extrasynthèse (Genay, France).

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).

Distilled water was obtained using the Milli-Q water purification system (Millipore, Bedford, MA, USA). Ethanol (96%), sodium acetate (99%) and iron (III) chloride hexahydrate were purchased from Kemika d.d. (Zagreb, Croatia), methanol and sodium bicarbonate from Gram-mol d.o.o. (Zagreb, Croatia), and sodium chloride from Lach-ner (Neratovice, Czech Republic). Maltodextrin (DE 4–7) was procured from Sigma-Aldrich (St. Louis, MO, USA), and β-cyclodextrin, gum arabic, 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) were from Acros Organics (Geel, Belgium). Pepsin, pancreatin, bile salts and 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH) were obtained from Sigma-Aldrich (St. Louis, MO, USA) and hydrochloric acid (37%) from Carlo Erba Reagents (Val-de-Reuil, France), while acetic acid was purchased from J.T.Baker (Deventer, The Netherlands). Standards for gallic acid, chlorogenic acid, protocatechuic acid, synaptic acid, ferulic acid, quinic acid, caffeic acid, p-coumaric acid, esculetin, quercetin-3-glucoside, kaempferol-3-glucoside, scopoletin and myricetin were obtained from Sigma-Aldrich (St. Louis, MO, USA) and catechin, epigallocatechin gallate, epicatechin gallate, luteolin, naringenin and apigenin were obtained from Extrasynthese (Genay, France).

HPLC grade ethyl acetate, methyl alcohol, acetic acid (99%), formic acid (98–100%) and toluene as well as analytical grade hydrochloric acid (37%), phosphoric acid (85%), ethyl alcohol and dichloromethane were purchased from Sigma-Aldrich (St. Louis, MO, USA) and Merck (Darmstadt, Germany). The anthocyanin standards (cyanidin-3,5-O-diglucoside, cyanidin-3-O-glucoside, delphinidin-3-O-glucoside, malvidin-3,5-O-diglucoside, malvidin-3-O-glucoside, delphinidin) and also (+)-catechin, (−)-epicatechin, (−)-epigallocatechin and (−)-epigallocatechin gallate were provided by Extrasynthese (Genay, Lyon area, France). The reagents for derivatization steps, namely 2-aminoethyl diphenylborinate (natural product reagent A, NP) and polyethylene glycol 400 (PEG 400), were obtained from Sigma Aldrich, while vanillin was bought from BDH (Poole, UK). Bidistilled water was used as solvent for each type of application method, i.e., extraction and sample preparation.

The solvents used for extraction (methanol, acetonitrile and formic acid) were purchased from Sigma-Aldrich Chemical Company (St Louis, MO, USA). A Milli-Q purification system (Millipore, Bedford, MA, USA) was used to prepare high-performance liquid chromatography (HPLC) grade water. Standards of gallic acid, caffeic acid, p-coumaric acid, ellagic acid, ferulic acid, sinapic acid, quinic acid, syringic acid, chlorogenic acid, phloridzin, kaempferol, luteolin, quercetin, isorhamnetin, myricetin, apigenin, epicatechin and catechin were purchased from Sigma-Aldrich. Standards of quercetin rhamnoside, isoquercetin, rutin, robinin, isorhamnetin rutinoside, neohesperidin, quercetin galactoside, myricitrin, myricetin galactoside, epigallocatechin, epigallocatechin gallate, procyanidin B1, procyanidin B2, cyanidin-3-O-glucoside, cyanidin-3-O-arabinoside, cyanin, delphinidin-3-O-glucoside, malvidin-3-O-glucoside, and pelargonidin-3-O-glucoside chloride were purchased from Extrasynthese (Genay, France).
The reference standard mixture of 37 FAME (FAME mix 37) was acquired from Supelco (Sigma-Aldrich, Bellefonte, PA, USA); other reference standards were purchased from Matreya Inc. (Pleasant Gap, PA, USA): PUFA-2, a nonconjugated 18:2 isomer mixture of individual PUFA, eicosapentaenoic acid, (EPA), docosahexaenoic acid (DHA), arachidonic acid (ARA), C18:3 cis-6,9,12, and C18:3 cis-9,12,15.