Folin–Ciocalteu reagent and sodium hydroxide (HPLC grade) were purchased from Chem-Lab NV (Zedelgem, Belgium), whereas DPPH (2,2-diphenyl-1-picrylhydrazyl) was from Sigma Aldrich (St. Louis, MO, USA). Gallic acid, used to prepare the calibration curve for the determination of phenolics, and Trolox ((S)-(−)-6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), used to determine antioxidant activity, were obtained from J&K Scientific GmbH (Pforzheim, Germany). Sodium carbonate was from Merck KGaA (Darmstadt, Germany). All of the other chemicals used were of analytical grade. Water used to make dilutions and solutions, as well as methanol, were of HPLC (high-performance liquid chromatography) gradient grade from Chem-Lab NV (Zedelgem, Belgium).
For elemental analysis, single certified element standard solutions (1000 mg/L) of trace elements Arsenic (As), Cadmium (Cd), Lead (Pb), Nickel (Ni), and Chromium (Cr), microelements Iron (Fe), Copper (Cu), Zinc (Zn), and Manganese (Mn), and macroelements Potassium (K), Calcium (Ca), Magnesium (Mg), and Sodium (Na) were obtained from Sigma Chem (St. Louis, MO, USA). All glassware and plastic containers used for elemental analysis were first soaked in nitric acid (10%), and then washed properly with ultrapure water in order to avoid cross-contamination. The rest of the chemicals and reagents used were of reagent grade.
For elemental analysis, single certified element standard solutions (1000 mg/L) of trace elements Arsenic (As), Cadmium (Cd), Lead (Pb), Nickel (Ni), and Chromium (Cr), microelements Iron (Fe), Copper (Cu), Zinc (Zn), and Manganese (Mn), and macroelements Potassium (K), Calcium (Ca), Magnesium (Mg), and Sodium (Na) were obtained from Sigma Chem (St. Louis, MO, USA). All glassware and plastic containers used for elemental analysis were first soaked in nitric acid (10%), and then washed properly with ultrapure water in order to avoid cross-contamination. The rest of the chemicals and reagents used were of reagent grade.