Malic acid

Acetonitrile of HPLC grade, acetic acid and N,O-bis(trimethylsilyl)trifluoroacetamide + 10% trimethylchlorosilane (BSTFA + 10% TMCS) were from Fischer Scientific (Pittsburgh, PA, USA). 5-O-caffeoylquinic acid, (+)-catechin, (−)-epicatechin, sucrose, glucose, fructose, citric acid, NaBH₄, N-methylimidazole, acetic anhydride, benzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3-phenylpropionic acid, phenylacetic acid, 3-hydroxyphenylacetic acid, 3-(4-hydroxyphenyl)propionic acid, dl-3-phenyllactic acid, dl-3-(4-hydroxyphenyl)lactic acid, 5-phenylvaleric acid, 3,4-dihydroxyphenylacetic acid and 2,4,5-trimethoxycinnamic acid and toluene-α−thiol were obtained from Sigma-Aldrich (Saint Quentin Fallavier, France). Phloretin, p-coumaric acid, quercetin and cyanidin-3-O-galactoside were obtained from Extrasynthese (Lyon, France). Phloridzin was obtained from Fluka (Buchs, Switzerland). Malic acid was obtained from R-Biopharm (Darmstadt, Germany). D3-Methanol was from Acros Organics (Geel, Belgium). Acetonitrile was analytical grade and from Fisher Scientific (Fair Lawn, NJ, USA). Ethyl acetate, dichloromethane and hexane obtained from VWR International (Radnor, PA, USA).

Acetonitrile of HPLC grade and acetic acid were from Fischer Scientific (Pittsburgh, PA, USA). 5-O-caffeoylquinic acid, (+)-catechin, (-)-epicatechin, sucrose, glucose, fructose, citric acid and toluene-α-thiol were from Sigma Aldrich (Darmstadt, Germany). Phloretin, p-coumaric acid, quercetin and cyanidin-3-O-galactoside were obtained from Extrasynthese (Lyon, France). Phloridzin was obtained from Fluka (Buchs, Switzerland). Malic acid was obtained from R-Biopharm (Darmstadt, Germany).