Magnesium chloride hexahydrate

HPLC grade methanol, acetone and methyl tert-butyl ether were acquired from Fisher Scientific Scharlau Chemie (Loughborough, UK), sodium chloride was purchased from POCH S.A.
(Sowińskiego, Poland). Ultrapure water was obtained with a Milli-Q system (Millipore Ibérica, Madrid, Spain). Magnesium chloride hexahydrate, ammonium carbonate, acetonitrile, hexane and ethanol (HPLC grade), acetic acid, ammonium acetate were purchased from Scharlab (Sentmenat, Spain). Calcium chloride dihydrate was obtained from Merck (Darmstadt, Germany). Sodium hydrogen carbonate and potassium dihydrogen phosphate were purchased from VWR (Llinars del Vallès, Spain). Butyl hydroxytoluene (BHT) was acquired from Scharlau Chemie S.A.
(Barcelona, Spain). Potassium chloride was obtained from Panreac (Castellar del Vallès, Spain).
All digestive enzymes (porcine α-amylase, porcine pepsin, porcine bile extract and porcine pancreatin) were purchased from Sigma-Aldrich (Darmstadt, Germany).
Caffeic acid, ferulic acid, p-coumaric acid and 5-O-caffeoylquinic acid commercial patterns were purchased from Sigma-Aldrich (St. Louis, MO, USA); and quercetin-3-O-glucoside from Extrasynthese (Genay, France). Phytoene and β-carotene standards were obtained from Carote-Nature (Ostermundigen, Switzerland), α-carotene was purchased from Supelco-Merck (Darmstadt, Germany) and lutein from Acros Organics (New Jersey, USA).

Hexaammineruthenium(III) chloride (Ru(NH 3 ) 6 Cl 3 ), phosphate buffered saline (PBS: 154 mM NaCl, 10 mM phosphate buffer, pH 7.4), sodium chloride, potassium chloride, sodium bicarbonate, calcium chloride, D-glucose (Sigma-Aldrich), magnesium chloride hexahydrate (Scharlau), monosodium phosphate (Biochemicals) and 98% sulfuric acid (RCI Labscan), were used as received. An artificial perilymph contained 125 mM NaCl, 3.5 mM KCl, 25 mM NaHCO 3 , 1.2 mM MgCl 2 , 1.3 mM CaCl 2 , 0.75 mM NaH 2 PO 4 and 5 mM glucose [18] . Electrodes were 2 mm, 0.6 mm or 25 µm diameter platinum discs (CH Instruments) or a cochlear implant with 22 half band, 0.3 mm 2 nominal area platinum electrodes (donated by Cochlear Ltd). One electrode of each type was tested. Disc electrodes were polished with 0.3 µm alumina slurry on Microcloth polishing cloth (Buehler), rinsed in deionised water and gently dried (Kimwipe) before use; the cochlear implant has not been used for in vivo studies and was not mechanically polished before use. Electrodes were tested in a 3 electrode configuration on a CHI660E potentiostat (CH Instruments) using a Ag/AgCl (3 M KCl) as reference electrode and Pt wire as counter electrode. The electrodes were connected to the potentiostat via alligator clips and placed into a beaker of solution. Unless indicated, test solutions were degassed with nitrogen for at least 10 min.