Sodium carbonate anhydrous

Hydrochloric acid, anhydrous sodium carbonate, and Folin–Ciocalteu reagent were purchased from Chempur (Piekary Śląskie, Poland). Gallic acid anhydrous, 2,2-diphenyl-1-picrylhydrazyl (DPPH), L-ascorbic acid, oxalic acid, m-phosphoric acid, 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox), and methanol were purchased from Sigma–Aldrich (Poznan, Poland). All reagents were of analytical grade.

The mesoporous silica materials, MCM-41 (<150 μm particle size, 2.1–2.7 nm pore size, hexagonal pore morphology), SBA-15 (<150 μm particle size, 6 nm pore size, hexagonal pore morphology), SBA-NH2 (<150 μm particle size, 6 nm pore size, amine functionalized), and SBA-SH (<150 μm particle size, 6 nm pore size, thiol functionalized), were purchased from Merck and used as received. All antioxidants (i.e., GA, PCA, CGA, and 4-HBA) were of analytical grade (HPLC purity > 97.0%) and purchased from Sigma-Aldrich. All aqueous solutions were prepared using ultrapure water (18.2 MΩ·cm, Milipore Simplicity System, Billerica, MA, USA). HPLC grade chemicals were obtained from J.T. Baker (Mallinckrodt Baker, Phillipsburg, NJ, USA). Reagents for the Folin–Ciocalteu method were as follows: ethanol 96% (v/v) (Emsure, Darmstadt, Germany), anhydrous sodium carbonate (purity > 99.5%, Chempur, Piekary Śląskie, Poland), Folin–Ciocalteu reagent (analytical grade, Chempur, Piekary Śląskie, Poland).

pH buffer solutions, hydrochloric acid, 0.1 M sodium hydroxide, anhydrous sodium carbonate, and Folin–Ciocalteu reagent were all analytical grade and purchased from Chempur (Piekary Śląskie, Poland). Disodium fluorescein of reagent grade, m-phosphoric acid, acetonitrile, and formic acid of HPLC gradient grade were purchased from Avantor Performance Materials Poland S.A. (Gliwice, Poland). Gallic acid anhydrous, phosphate-buffered saline (PBS), 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH), (±)-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox), methanol, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were reagent or analytical grade, purchased from Sigma-Aldrich Sp. z.o.o (Poznań, Poland). Pure water (resistivity of 18.0 MΩ·cm) was also used in the research.