Acetonitrile hypergrade for lc ms

[²H₇]-Labeled ADMA hydrochloride und [²H₇]-labeled L-Arginine hydrochloride were obtained from EURISO-TOP (Saint-Aubin, France). The isotope labeled BAIB standard ([²H₆]-BAIB) was a kind gift of Dr. Ute Hofmann (Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart, Germany) [17] (link). The isotope labeled SDMA ([²H₆]-SDMA) was obtained from Toronto Research Chemicals Inc. (Toronto, Canada). ADMA dihydrochloride and SDMA dihydrochloride were purchased from Enzo Life Sciences GmbH (Lörrach, Germany). L-Arginine was purchased from Sigma-Aldrich Chemie GmbH (Steinheim, Germany). Acetonitrile hypergrade for LC-MS and SUPRAPUR® formic acid (98%) were obtained from Merck (Darmstadt, Germany), and Baker Analyzed LC-MS-Reagent Water was from Mallinckrodt Baker B.V. (Deventer, Netherland). The AGXT2-dependent metabolite DM’GV was synthesized as described in detail in the figure S1.

Dapoxetine hydrochloride ((S)-N,N-dimethyl-1-phenyl-3-(1-naphthalenyloxy)propanamine hydrochloride, purity ≥ 98%), water (LC–MS grade), β-nicotinamide adenine dinucleotide 2′-phosphate-reduced tetrasodium salt hydrate (NADPH), HLM, sodium phosphate monobasic monohydrate salt and sodium phosphate dibasic anhydrous salt were obtained from Sigma-Aldrich (St. Louis, CA, USA). Acetonitrile (hypergrade for LC–MS) was purchased from Merck (Darmstadt, Germany) and 98% formic acid (MS grade) was obtained from Fluka (Taufkirchen, Germany).

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.