6 hydroxyl 2 5 7 8 tetramethyl chroman 2 carboxylic acid

The following chemicals and reagents were purchased from Sigma-Aldrich Italia (Milan, Italy): Folin–Ciocalteu’s phenol reagent, 6-hydroxyl-2,5,7,8-tetramethyl-chroman-2-carboxylic acid (Trolox), 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid; ABTS), AlCl₃, NaNO₂, FeCl₂, FeCl₃, FerroZine^®, fluorescein, 2,2-azobis(2-amidinopropane) dihydrochloride (AAPH), phosphoric acid (85–87%, w/w), hydrochloric acid (37%, w/w), monobasic sodium phosphate (>98%), sodium hydroxide beads (>98%), and HPLC-grade solvents. Pure standards of phenolic acids (4-hydroxybenzoic, gallic, caffeic, chlorogenic, ferulic, p-coumaric, sinapic, syringic, trans-cinnamic, and vanillic acids) and flavonoids (quercetin, quercetin-3-O-glucoside, quercetin-3-O-rutinoside, quercetin-3-O-galactoside, kaempferol, kaempferol-3-O-rutinoside, catechin, epicatechin, daidzein, and genistein) were purchased from Extrasynthese (Genay Cedex, France). The IUPAC names for these compounds are indicated in Table S1. All standards (>99.5% purity in powder form) were prepared as stock solutions at 1 mg/mL in methanol and stored in the dark at −18 °C for less than three months.

2,2-Diphenyl-1-picrylhydrazyl (DPPH), 6-hydroxyl-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), 5,5-dimethyl-1-pyrroline N-oxide (DMPO), riboflavin, hydrogen peroxide (30%, H₂O₂), dimethyl sulfoxide (DMSO), 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH), fluorescein, Folin–-Ciocalteu’s phenol reagent, quercetin, gallic acid, chloroform-d, acetone-d₆ and methanol-d were purchased from Sigma Aldrich (St. Louis, MO, USA). pBR322 plasmid DNA was purchased by Thermo Fisher Scientific (Waltham, MA, USA). Silica gel (230–400 mesh), NP F254 and RP-18 F254 TLC plates were obtained from Merck (Darmstadt, Germany). Spherical C18 100 Å reversed phase silica gel (particle size: 20–40 μm) was obtained from SILICYCLE (Ville de Québec, QC, Canada). Sodium hydroxide, ethylenediamine tetraacetic acid, disodium dehydrate (EDTA), iron (II) sulfate heptahydrate (FeSO₄), sodium nitrite (NaNO₂), sodium carbonate anhydrous (Na₂CO₃), aluminium chloride (AlCl₃), methanol, acetone, ethylacetate, chloroform and n-hexane were purchased from Duksan Co. (Gyenggi, Korea).