Folin ciocalteu reagent

The solvents used for LC–MS analyses (acetonitrile, formic acid and water) were of spectroscopic grade and were purchased from J. T. Baker (Center Valley, PA, USA). The solvents used to perform extraction (ethanol, water, ethyl acetate, acetone, methanol) were of analytical grade and were obtained from Avator Performance Materials (POCH, Gliwice, Poland). Folin–Ciocalteu reagent, sodium carbonate, DMSO and citric acid were bought from Stanlab (Lublin, Poland). Standards of catechins (EGC, EGCG, ECG, C and EC), gallic acid, DPPH (2,2-diphenyl-1-picrylhydrazyl) and Trolox were purchased from Sigma-Aldrich (St. Louis, MO, USA).

The following chemical reagents were used in the present experiments: dimethyl sulfoxide (DMSO, ≥99%, Stanlab, Lublin, Poland), methanol (≥99%, Stanlab, Lublin, Poland), Folin-Ciocalteu reagent (AKTYN, Suchy Las, Poland), sodium carbonate (≥99%, Stanlab, Lublin, Poland), gallic acid (≥98%, Sigma Aldrich, Poznań, Poland), 2,2-diphenyl-1-picrylhydrazyl, (DPPH, Sigma Aldrich, Poznań, Poland), 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox, ≥98%, Sigma Aldrich, Poznań, Poland), iron(II)sulfate (≥99%, Sigma Aldrich, Poznań, Poland), ferrosine (97%, Sigma Aldrich, Poznań, Poland), ethylenediaminetetraacetic acid (EDTA, ≥ 99%, Sigma Aldrich, Poznań, Poland), diethyl ether (≥98%, Sigma Aldrich, Poznań, Poland), aluminium chloride hexahydrate (≥99%, POCH), quercetin (≥95%, Sigma Aldrich), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS, Sigma Aldrich, Poznań, Poland), potassium persulfate (≥99%, Sigma Aldrich, Poznań, Poland), acetonitrile (≥99.9%, Sigma Aldrich, Poznań, Poland), formic acid (≥98%, Sigma Aldrich, Poznań, Poland), hydrochloric acid (Fluka, Poznań, Poland) and sodium hydroxide (Sigma Aldrich, Poznań, Poland).

All reagents used for metal analysis—nitric (V) acid (65%) and hydrochloric acid (36%)—were of Suprapur Grade and purchased from Merck (Darmstadt, Germany). Certified stock solutions of the investigated elements (1000 mg/L, Merck) were used to plot calibration curves for each metal. An Ultrapure Millipore Direct-Q-R 3UV system (Merck) allowed us to obtain high purity deionized water (resistivity 18.2 MWcm), which was used during all spectroscopic analysis (including the digestion process). Polypropylene tubes were used to store the digests obtained during metal analysis.
The solvents used during LC-MS determinations (acetonitrile, formic acid and water) were of spectroscopic grade and were purchased from J. T. Baker (Center Valley, PA, USA). Standards of catechins (C, EGC, EGCG, ECG, and EC), gallic acid, DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS [2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] diammonium salt) and trolox were bought from Sigma-Aldrich (St. Louis, MO, USA). Folin-Ciocalteu reagent, sodium carbonate and citric acid were bought from Stanlab (Lublin, Poland), whereas potassium persulfate (analytical grade) from POCH Polish Chemicals Reagents (Gliwice, Poland).