Ethyl gallate

All reagents employed, unless otherwise stated, were of analytical grade. Standards of arbutine, resveratrol, ethyl gallate, syringaldehyde, polydatin, tyrosol, umbelliferon, 4-hydroxybenzoic acid, caffeic acid, chlorogenic acid, gallic acid, homogentisic acid, p-coumaric acid, vanillic acid, ferulic acid, syringic acid, and trans-cinnamic acid were obtained from Sigma-Aldrich (Steinheim, Germany). The structures and CAS numbers of all studied phenolic compounds are summarized in Table 1. Stock standard solutions of all phenolics (ca. 1000 mg/L) were prepared in methanol in amber glass vials. Intermediate working solutions were then prepared by appropriate dilution with Milli-Q water. All stock solutions were stored at 4 °C.
Methanol and acetonitrile (both UHPLC-gradient grade), absolute ethanol and acetone were purchased from Panreac (Barcelona, Spain). Water was purified using an Elix 3 coupled to a Milli-Q system (Millipore, Bedford, MA, USA) and filtered through a 0.22 µm nylon membrane integrated into the Milli-Q system.

Folin–Ciocalteu, gallic acid, catechin, epicatechin, caffeine, ethyl gallate, rutin, ellagic acid, quercetin, quercitrin, apigenin, chlorogenic acid, DPPH, ABTS, acarbose, pancreatic α‐amylase, and yeast α‐glucosidase were purchased from Sigma‐Aldrich. Maltodextrin (MAX1000® series, Matsutani Chemical Industry Co., Ltd.) was acquired from DKSH Management Ltd., Vietnam. Xilong Scientific Co. Ltd. supplied ethanol, methanol, and acetic acid. All chemicals and reagents were of analytical grade.

The chemicals ethyl gallate, bovine serum albumin (BSA) and Calf thymus DNA (CT-DNA) were purchased from Sigma-Aldrich Chemical Co (St Louis, MO. USA). pBR322 DNA was purchased from GENEI (Bangalore, India). Biochemical kits were obtained from Span diagnostics (Surat, Gujarat, India), and all other reagents used were of analytical grade.

Lutein, β-cryptoxanthin, β-carotene, lycopene, ammonium acetate, butylatedhydroxytoluene (BHT), sodium hydroxide, potassium hydroxide, L-ascorbic acid, Na₂-ethylenediaminetetraacetic acid, ethyl gallate, and HPLC-grade denatured ethanol were from Sigma-Aldrich (St. Louis, MO). Solvents including ethyl acetate, methanol, isopropyl alcohol, acetone, petroleum ether, hexanes and HCl were purchased from Mallinckrodt Baker (Phillipsburg, NJ, USA). Echinenone, α-cryptoxanthin and α-carotene were from CaroteNature (Lupsingen, Switzerland). Zeaxanthin was from IndoFine (Hillsborough, NJ).

EGCG, ECG, EGC, and EC were purchased from Toronto Research Chemicals (Toronto, ON, Canada). Ascorbic acid, ethylenediaminetetraAcetic acid (EDTA), sodium phosphate monobasic, ethyl acetate, and ethyl gallate (internal standard, I.S.) were obtained from Sigma-Aldrich (St. Louis, MO, USA). Acetonitrile and methanol (Merck, Darmstadt, Germany) were HPLC grade. Acetic acid was purchased from Duksan (Gyeonggi-do, Korea).

Ethyl gallate, 4-hydroxybenzaldehyde, vanillin, tyrosol, protocatechuic aldehyde, syringaldehyde, pyrogallol, 4-hydroxy-3-methoxycinnamaldehyde, 4-methylcatechol, tryptophol, ethyl 3,4-dihydroxycinnamate, 2,6-dimethoxyphenol, ethyl vanillate, homovanillyl alcohol, eugenol, 4-hydroxy-3-methoxyphenylacetone, salicylaldehyde, coniferyl alcohol, epicatechin, catechin, scopoletin, p-coumaric acid, caffeic acid, resveratrol, syringic acid, rutin, gallic acid, salicylic acid, protocatechuic acid, 2-methoxy-4-vinylphenol, 4-vinylphenol, 4-ethylguaiacol were purchased from Sigma-Aldrich (Steinheim, Germany). All chemicals were used in the highest purity available. Acetonitrile and methanol (gradient grade for liquid chromatography) were also purchased from Sigma-Aldrich. Deionized water was produced by Mili-Q^® Reference System (Merck KGaA, Darmstadt, Germany). Sodium chloride was purchased by Lach-Ner (Neratovice, Czech Republic). Standard solution of n-alkanes C8-C33 was purchased by CPAchem (Stara Zagora, Bulgaria). Technical gases, i.e., helium 4.6, hydrogen, and nitrogen, were purchased from Linde Gas (Prague, Czech Republic).

The following polyphenols standards were used in this study: gallic acid, rutin, vanillic acid, 3,4-dihydroxybenzoic acid, syringic acid, chlorogenic acid, 3,4-dihydroxybenzaldeyde, ethyl gallate, 4-hydroxybenzoic acid, ferulic acid, epicatechin, naringenin, p-coumaric acid, 2,5-dihydroxybenzoic acid, quercetin, and apigenin, and were supplied by Sigma Aldrich (St. Louis, MO, USA). Caffeic and caftaric acids were purchased from Chengdu Biopurify Pytochemicals (Chengdu, China). Catechin, 3-hydroxytyrosol, myricetin, and resveratrol were obtained from TCI (Tokyo, Japan). Oleuropein and homogentisic acid were purchased from Extrasynthese (Genay, France). Luteolin was obtained from Carbosynth (Berkshire, UK). Hesperidin and kaempferol were supplied by Glentham Life Sciences (Corsham, UK). The solvents used were HPLC-UV-grade acetonitrile (ACN) from Fisher Scientific (Madrid, Spain), HPLC-UV-grade ethanol (EtOH) obtained from Honeywell Riedel-de HaënTM (Seelze, Germany), and formic acid (FA) 98–100% (w/w) from Merck (Darmstradt, Germany). Ultrapure water was produced by a Milli-Q system (Merck Millipore).