Anhydrous sodium carbonate

Methanol and chloroform of high-performance liquid chromatography (HPLC) grade, hydrochloric acid (37%), sulfuric acid (98%), and methylene blue were purchased from VWR (Radnor, PA, United States). Sodium hydrogen carbonate and anhydrous sodium carbonate were obtained from CARLO ERBA Reagents (Milan, Italy). SLES of technical grade purity was from BOC Sciences (Shirley, NY, United States). The stock solution of SLES (1,000 mg/L) was prepared in methanol and stored at −20°C. The dilution of this stock solution was performed using ultrapure water. Ultrapure water (18 MΩ⋅ cm quality) was obtained using a Milli-Q system Millipore (Bedford, MA, United States). Diatomaceous earth was purchased from Thermo Fisher Scientific Inc. (Waltham, MA, United States).

All solvents and reagents were of high quality with a high grade of purity. Ethanol ≥ 99.9% ACS for analysis was obtained from VWR International (Milano, Italy). Hydrochloric acid 37% RPE for analysis, potassium bicarbonate, anhydrous sodium carbonate for analysis, and gallic acid ACS for analysis were obtained from Carlo Erba (Milano, Italy). Methanol for HPLC, n-hexane anhydrous at 95%, chloroform for chromatography, and 1-butanol ACS reagent ≥ 99.5 were acquired from Sigma-Aldrich Chemical Company (Milano, Italy). Folin–Ciocâlteu reagent and acetonitrile hypergrade for LC–MS were purchased from Merck Millipore GmbH (Milano, Italy). 2,2-Diphenyl-1-picrylhydrazyl (DPPH^⋅) was obtained from Alfa Aesar (Thermo Fisher Scientific companies in Rodano, Milano, Italy). Malvidin-3-O-glucoside, naringin, catechin, quercetin, gallic acid, vanillic acid, caffeic acid, ferulic acid, and amino acid mixture were purchased from Merck (Milano, Italy).
Bidistilled water was utilized throughout the preparation of the solutions. The extracts obtained from the different fruits of Arbutus unedo L. were used without any purification, and all the analyzed solutions, where necessary, were prepared by diluting the stock solutions of the extracts in water or in a hydroalcoholic solution.