2 3 dimethoxybenzoic acid

All the phenolic chemical standards (gallic acid, catechin, chlorogenic acid, p-hydroxybenzoic acid, vanillic acid, epicatechin, syringic acid, 3-hydroxybenzoic acid, 3-hydroxy-4-methoxy-benzaldehyde, p-coumaric acid, rutin, sinapic acid, trans-ferulic acid, naringin, 2,3-dimethoxy-benzoic acid, benzoic acid, o-coumaric acid, quercetin, trans-cinnamic acid, naringenin) (purity ˃ 98%) were purchased from Sigma Aldrich (Milan, Italy). Methanol (HPLC-grade), formic acid (99%), nitric acid (65%, supra-pure metal grade) and sulfuric acid (98%, ultrapure grade) were obtained from Carlo Erba Reagents (Milan, Italy). Double-distilled water was obtained using a Millipore Milli-Q Plus water treatment system (Millipore Bedford Corp., Bedford, MA, USA). Standard metal solutions of Cd(II), Cu(II), Pb(II) and Zn(II) (1000 mg L⁻¹, suprapure grade), hydrochloric acid (30%) and sodium acetate (anhydrous, analytical grade) were purchased by Merck (Darmstad, Germany). Anthraquinone chemical standards (all ˃99%) were purchased from Extrasynthese (Genay, France).

Tondino del Tavo (Loreto Aprutino, Pescara, Abruzzo, Italy) and Cannellino Bio (Colfiorito, Perugia, Umbria, Italy) were selected as the common bean variety (Phaseolus vulgaris) belonging to the genus Phaseolus. They were collected and stored according to their use for human consumption. Tondino del Tavo was purchased at the Passeri Carlo Company (Loreto Aprutino, Pescara) and Cannellino Bio (Colfiorito, Perugia) at a local market. Methanol, ethanol, n-hexane, ethyl acetate and acetonitrile for HPLC, NaOH, HCl and NaCl were purchased at Sigma Aldrich (Milan, Italy). Gallic acid, catechin, chlorogenic acid, p-hydroxybenzoic acid, vanillic acid, epicatechin, syringic acid, p-coumaric acid, rutin, ferulic acid, sinapinic acid, 3-hydroxybenzoic acid, 3-hydroxy-4-methoxybenzoc acid, naringin, 2,3-dimethoxybenzoic acid, o-coumaric acid, quercetin, cinnamic acid, carvacrol and naringenin were purchased at Sigma Aldrich (Milan, Italy). The centrifuge was an Eppendorf 5702 (Hamburg, Germany). The lyophilisator was a Buchi L-100 (BUCHI Italia s.r.l. Cornaredo, Italy).

Chemical standards of phenolic compounds (benzoic acid, carvacrol, catechin, chlorogenic acid, t-cinnamic acid, 8-cinnamoyl harpagide (harpagoside), o-coumaric acid, p-coumaric acid, 2,3-dimethoxybenzoic acid, epicatechin, t-ferulic acid, gallic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 3-hydroxy-4-methoxybenzaldehyde, naringin, naringenin, quercetin, rutin, sinapinic acid, syringic acid, vanillic acid (all purity > 98%)), β-cyclodextrin (≥97%), n-hexane (HPLC-grade), diethyl ether (≥99%), and chloroform (HPLC-grade) were purchased from Sigma-Aldrich (Milan, Italy).
Ethyl acetate (≥99%), acetonitrile (HPLC-grade), methanol (HPLC-grade), ethanol (HPLC-grade), acetic acid (≥99%) as well as d-(+)-glucose were obtained from Carlo Erba Reagents (Milan, Italy). Sodium chloride (≥99%) was obtained from Honeywell (Seelze, Germany). NADES (glycolic acid/betaine mixture) was newly synthesized and supplied by University of Perugia. It was chosen between differently structured novel DES and NADES mixtures for its suitable properties (low freezing point and low viscosity, absence of aromatic compounds in its composition, low cost and natural source of the molecules forming it). Ultra-pure water was obtained using a Millipore Milli-Q Plus water treatment system (18 MΩ cm at 23 °C, Millipore Bedford Corp., Bedford, MA, USA).