Hesperidin

The following polyphenols standards were used in this study: gallic acid, rutin, vanillic acid, 3,4-dihydroxybenzoic acid, syringic acid, chlorogenic acid, 3,4-dihydroxybenzaldeyde, ethyl gallate, 4-hydroxybenzoic acid, ferulic acid, epicatechin, naringenin, p-coumaric acid, 2,5-dihydroxybenzoic acid, quercetin, and apigenin, and were supplied by Sigma Aldrich (St. Louis, MO, USA). Caffeic and caftaric acids were purchased from Chengdu Biopurify Pytochemicals (Chengdu, China). Catechin, 3-hydroxytyrosol, myricetin, and resveratrol were obtained from TCI (Tokyo, Japan). Oleuropein and homogentisic acid were purchased from Extrasynthese (Genay, France). Luteolin was obtained from Carbosynth (Berkshire, UK). Hesperidin and kaempferol were supplied by Glentham Life Sciences (Corsham, UK). The solvents used were HPLC-UV-grade acetonitrile (ACN) from Fisher Scientific (Madrid, Spain), HPLC-UV-grade ethanol (EtOH) obtained from Honeywell Riedel-de HaënTM (Seelze, Germany), and formic acid (FA) 98–100% (w/w) from Merck (Darmstradt, Germany). Ultrapure water was produced by a Milli-Q system (Merck Millipore).

The main standards used in the experiments were 4-hydroxybenzoic acid, vanillic acid, rutin, syringic acid, gallic acid, ferulic acid, p-coumaric acid, and naringenin, purchased from Sigma Aldrich (St. Louis, MO, USA); kaempferol and hesperidin were obtained from Glentham Life Sciences (Corsham, UK); and caffeic acid was obtained from Chengdu Biopurify Pytochemicals (Sichuan, China). The solvents were prepared with acetonitrile (ACN, HPLC-UV grade) from Fisher Scientific (Loughborough, UK), formic acid (98–100% w/w) from Merck (Darmstradt, Germany), and water (purified with a Milli-Q equipment, Merck Millipore, Darmstradt, Germany).

Methanol (Chromosolv^TM for HPLC, ≥99.9%) and acetonitrile (UHPLC supergradient ACS quality) were obtained from PanReac AppliChem (Barcelona, Spain), formic acid (≥98%) from Sigma-Aldrich (St Louis, MO, USA), and hydrochloric acid (37%) from Fisher Chemical (Geel, Belgium). Water was purified by employing an Elix 3 system coupled to a Milli-Q instrument from Millipore Corporation (Bedford, MA, USA). The water was filtered with a 0.22 µm nylon membrane filter integrated into the Milli-Q instrument.
All the polyphenolic and phenolic acid compounds used in this work were of analytical grade and were obtained from Sigma-Aldrich, with the exception of hesperidin obtained from Glentham Life Sciences (Lorsham, United Kingdom), astilbin and caftaric acid from Biopurity Phytochemicals Ltd. (Chengdu, Sichuan, China), trans-coumaric acid and procyanidin C1 from Phytolab (Vestenbergsgreuth, Germany), diosmin, hesperetin, and catechol from AlfaAesar Chemicals (ThermoFisher, Kandel, Germany), naringin, naringenin, and epigallocatechin from Biosynth-Carbosynth (Berkshire, United Kingdom), procyanidins B2 and A2 from Extrasynthese (Genay, France), pinocembrin from Fisher Scientific (Madrid, Spain), tricetin and galangin from Cymit Quimica S.L. (Barcelona, Spain), and chrysin and pinobanksin from Merck (Darmstadt, Germany).