2 2 diphenyl 1 picryl hydrazyl radical dpph d9132

Caffeic acid (C0625, 99%), p-coumaric acid (C9008, ≥98%), gallic acid (27645, ≥99%), epicatechin (E1753, ≥90%), 2,2-diphenyl-1-picryl-hydrazyl radical (DPPH, D9132), Carrez Reagent I (MAK191A), Carrez Reagent II (MAK191B) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Orto-phosphoric acid 85%, HPLC grade, methanol HPLC grade, hydrochloric acid 36.2% were purchased from Fluka (Buchs, Switzerland) and sodium carbonate and Folin-Ciocalteu reagent from Kemika (Zagreb, Croatia).

Acetonitrile and acetic acid (both MS grade) and methanol (HPLC grade) were purchased from Merck (Darmstadt, Germany). The 2,2-Diphenyl-1-picrylhydrazyl radical (DPPH^•) (D9132) and phenolic standards were supplied by Sigma-Aldrich (Steinheim, Germany). Trolox ((±)-6-hydroxy-2,5,7,8-tetramethyl-chromane-2-carboxylic acid) (56510) was purchased from Fluka (Buchs, Germany). Sodium carbonate and Folin–Ciocalteu reagent were obtained from Kemika (Zagreb, Croatia).
To prepare the standard solutions and blanks, ultra-pure water (Thermo Fisher TKA MicroPure water purification system, 0.055 µS/cm, Niederelbert, Germany) was used. Syringe filters (13 mm, PTFE membrane 0.45 µm) were supplied by Supelco (Bellefonte, PA, USA).

Chlorogenic acid (C3878, ≥ 95%), caffeic acid (C0625, 99%), ferulic acid (F3500, 99%), p-coumaric acid (C9008, ≥ 98%), sinapic acid (D7927, ≥ 98%), 3,5-dihydroxybenzoic acid (D10,000, 97%), and 2,2-diphenyl-1-picryl-hydrazyl radical (DPPH, D9132) were purchased from Sigma–Aldrich (St. Louis, MO, USA). Orto-phosphoric acid 85%, HPLC grade, methanol HPLC grade, hydrochloric acid 36.2% were purchased from Fluka (Buchs, Switzerland) and Folin–Ciocalteu reagent and sodium carbonate from Kemika (Zagreb, Croatia).