Potassium hydroxide koh

Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) (Sigma-Aldrich, Steinheim, Germany), ABTS (2,20-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (Sigma-Aldrich, Steinheim, Germany), potassium persulfate (Sigma-Aldrich, Steinheim, Germany), acetic acid (Sigma-Aldrich, Steinheim, Germany), TPTZ (2,4,6-tripyridyl-1,3,5-triazine) (Sigma-Aldrich, Steinheim, Germany), ferric chloride (FeCl₃) (Sigma-Aldrich, Steinheim, Germany), methanol, boron trifluoride (BF₃) (Sigma-Aldrich, Steinheim, Germany), Supelco 37 FAME Mix C4–C24 Component (Sigma-Aldrich, Steinheim, Germany), Hydrochloric acid (HCl) (Chempur, Piekary Śląskie, Poland), chloroform (Chempur, Piekary Śląskie, Poland), potassium hydroxide (KOH) (Chempur, Piekary Śląskie, Poland), sulphuric acid (H₂SO₄) (Chempur, Piekary Śląskie, Poland), Folin–Ciocalteu reagent (Chempur, Piekary Śląskie, Poland), sodium carbonate (Na₂CO₃) (Chempur, Piekary Śląskie, Poland), sodium sulfate (Na₂SO₄) (Chempur, Piekary Śląskie, Poland), butylated hydroxytoluene (BHT) (AppliChem, Darmstadt, Germany).

High-purity reagents and catalysts for liquid chromatography (HPLC-grade) were used for sample preparation. Concentrated hydrochloric acid (HCl, 37%) was purchased from VWR™ International (Paris, France); 25% ammonium hydroxide solution (NH₃ × H₂O); and potassium hydroxide (KOH, purity ≥ 85%) was acquired from Chempur (Piekary Śląskie, Silesia, Poland). Phenol (C₆H₅OH) (purity > 99%) and LC-MS-grade formic acid (HCOOH, puris r.a.) were purchased from Sigma-Aldrich (Darmstadt, Germany). A mixture of 17 amino acids (AAs) in liquid form with concentrations ranging from 1.25 to 2.6 µM mL was purchased from Merck KGaA (Darmstadt, Germany) and used as an external standard for constructing calibration curves. LC-MS-grade acetonitrile (MeCN) was ordered from the same source. Ultra-pure MS-grade isopropyl alcohol (C₃H₈O, purity ≥ 99.95%) was purchased from Biosolve Chimie (Dieuze, France). Ultra-pure water was produced using a reverse osmosis PureLab Flex Elga water purification system (Veolia Water Technologies, Paris, France).

Analytical-grade reagents and solvents, i.e., Folin–Ciocalteu reagent from Sigma-Aldrich (Saint Louis, MO, USA), anhydrous sodium sulfate (Na₂SO₄), chloroform, diethyl ether, ethanol (99.9% purity), formic acid, methanol, potassium hydroxide (KOH), sodium carbonate (Na₂CO₃), sulfuric acid (H₂SO₄), and zinc purchased from Chempur (Piekary Śląskie, Poland) were used. Chromatography-grade solvents, i.e., dichloromethane, ethanol, methanol, n-hexane, heptane, methyl tert-butyl ether, iso-propanol, pyridine, and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS) were purchased from Sigma-Aldrich (Saint Louis, MO, USA). Analytical standards such as 5α-cholestane, margaric acid, β-apo-8’-carotenal, D-catechin, phenolic acids (p-coumaric acid (p-CA), dihydroferulic acid (DHFA), sinapic acid (SA), vanillic acid (VA)), and 4-vinylguaiacol (4-VG) were purchased from Sigma-Aldrich (Saint Louis, MO, USA), while tocopherols (α-, γ-, and δ-tocopherol) were purchased from Calbiochem (Nottingham, UK). Deionized water was obtained from HLP 5 deionizer (Hydrolab, Gdańsk, Poland).