Catechin

Dehulled seeds of organic black quinoa (Chenopodium quinoa Willd.), labelled as originating from Bolivia (South America) and packed in a protective atmosphere, were purchased in a retailer specialized in organic and biodynamic products in Italy. Proximate composition per 100 g was, as reported in the nutrition label: 380 kcal energy; 6.2 g fat, of which 0.7 g saturates; 65 g carbohydrates, of which 4.0 g sugars; 9.0 g fibre; 12 g protein; and 0.01 g salt.
Folin–Ciocalteu’s Reagent, methanol, ethanol, acetone, acetic acid and acetonitrile were purchased from Carlo Erba Reagents (Milan, Italy).
Caffeic acid, (+)-catechin, o-coumaric acid, p-coumaric acid, (−)-epicatechin, 3,4-dihydroxycinnamic acid, t-ferulic acid, gallic acid, gentisic acid, 4-hydroxybenzoic acid, protocatechuic acid, rutin, sinapic acid, syringic acid, vanillic acid, and vanillin were purchased from Extrasynthèse (Geney, France) and Sigma-Aldrich (St. Louis, MO, USA).
HPLC grade solvents and water purified by a Milli-Q system (Millipore Corp., Billerica, MA, USA) were used in HPLC analysis.

The compounds 2,2′-Azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ), methanol acetic acid, phloroglucinol, β-cyclodextrin, and K₂S₂O₅ were purchased from Sigma-Aldrich (Steinheim, Germany). On the other hand, (−)-epicatechin, (+)-catechin, procyanidin B2, chlorogenic acid, neochlorogenic acid, cryptochlorogenic acid, caffeic acid, dicaffeoylquinic acid, p-coumaric acid, myricetin, isoquercitrin, cyanidin-3-O-galactoside, and cyanidin-3-O-glucoside were purchased from Extrasynthese (Lyon, France). Acetonitrile for ultra-performance liquid chromatography (UPLC; Gradient grade) and ascorbic acid were from Merck (Darmstadt, Germany). Yeasts S. cerevisiae and S. bayanus were purchased from Eaton company (Sandomierz, Poland).

Formic acid, methanol, AA (L(+) ascorbic acid), AAPH (2,2′-azobis(2-amidinopropane)hydrochloride), MC540 (merocyanine 540), and enzyme COX-2 (cyclo-oxygenase) were purchased from Sigma-Aldrich (Steinheim, Germany). Acetonitrile was purchased from Merck (Darmstadt, Germany). Quercetin-3-O-glucoside, quercetin 3-O-galactoside, quercetin-3-O-rutinoside, (+)catechin, (−)epicatechin, procyanidin B2-3-O-gallate, procyanidin B3, vitexin, and luteolin-3-O-glucoside were purchased from Extrasynthese (Lyon, France). The DPH-PA (3-(4-(6-phenyl)-1,3,5-hexatrienyl) phenylpropionic acid), Laurdan ((6-dodecanoyl-2-dimethylaminonaphthalene)), and DPH (1,6-diphenyl-1,3,5-hexatriene) fluorescence probes were purchased from Life Technologies (California, USA).

The following HPLC- or LC-MS-grade reagents were used for analyses: acetonitrile, L-ascorbic acid, methanol (Sigma-Aldrich, Poland), acetic acid (Baker, Poland), and formic acid (VWR Int., Poland). The qualitative and quantitative content of polyphenolic compounds was determined with the following standards: 3,4-dihydroxybenzoic acid, 4-hydroxybenzoic acid, chlorogenic acid, caffeic acid, gallic acid, isovanilic acid, kaempferol, luteolin, neochlorogenic acid, orientin (luteolin-8-glucoside), p-coumaric acid, procyanidin B2, quercetin, quercetin-3-O-glucoside (Sigma-Aldrich, Poland), (+)-catechin, (–)-epicatechin, quercetin-3-O-galactoside, quercetin-3-O-rutinoside, quercetin-3-O-vicianoside (Extrasynthese, France), cyanidin-3-O-arabinoside, cyanidin-3-O-galactoside, cyanidin-3-O-glucoside (Polyphenols Laboratories AS, Norway) and cyanidin-3-O-xyloside (Toronto Research Chemicals, Canada).

The organic solvents used for mobile phases and extractions (methanol, acetonitrile) were of LC–MS purity and were acquired from Carl Roth (Carl Roth, Germany). The ultrapure water and MS-grade formic acid was manufactured by Fisher Chemical (Thermo Fisher Scientific, Waltham, MA, USA). For the colorimetric determinations (Folin-Ciocâlteu’s phenol reagent, Na₂CO₃, NaNO₂, AlCl₃, NaOH, vanillin, glacial acetic acid, perchloric acid, HCl, PVP) and antioxidant assays (DPPH, Trolox, CH₃COONa, TPTZ, FeCl₃, CH₃CO₂NH₄, CuCl₂, neocuproine, Na₂S₂O₈, ABTS), the substances were purchased from Sigma (Merck, Germany), while the HPLC-grade standards (gallic acid, rutin, corosolic acid, catechin) were acquired from Extrasynthese (Genay, France).

2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) were purchased from Sigma Aldrich (Schnelldorf, Germany). Methanol (LC-MS grade) was purchased from Chem-Lab (Zedelgem, Belgium). Formic acid (LC-MS grade) was purchased from Fischer Scientific (Madrid, Spain); Trolox was purchased from Acrὸs organics (Morris, NJ, USA). Water (LC/MS grade) was purified using a Millipore Direct-Q 3UV apparatus (18.2 mΩ*sec). Standard compounds (catechin, procyanidin B1, epicatechin, chlorogenic acid, myricetin glucoside, kaempferol glucoside, quercitrin, quercetin 3.4-di-O-glucoside, quercetin, kaempferol, rutin, amentoflavone, hypericin) were purchased from ExtraSynthese (Genay, France) and hyperforin was purchased from ChromaDex (Los Angeles, CA, USA).