title: Effects of metal ions (Cu²⁺, Fe²⁺ and Fe³⁺) on HPLC analysis of catechins.
abstract: Catechins [(-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG)] were analysed by HPLC using an ODS column, an electrochemical detector (0.75V vs. Ag/AgCl) and an eluting solvent composed of water containing buffer (84% v/v), acetonitrile (12% v/v) and ethylacetate (4% v/v) in the presence of metal ions (Cu(2+), Fe(2+) and Fe(3+)). HPLC peaks were affected by metal ions: the peak intensities of ECG and EGCG decreased, but the peak intensities of EC and EGC were not affected seriously. Fe(2+) most markedly decreased the peak intensities of EGCG. EDTA was added to mask metal ions and an optimum condition was proposed. The effects of the metal ions on HPLC analysis are discussed from the viewpoints of metal complex formation with catechins and oxidation of catechins on the basis of ultraviolet-visible (UV-vis) spectrophotometry, electrospray ionisation mass spectrometry (ESI-MS) and cyclic voltammetry (CV).
authors: Department of Health and Nutrition Science, Nishikyushu University, Kanzaki, Saga 842-8585, Japan. Electronic address: midori@nisikyu-u.ac.jp.
authors: Midori
authors: M
authors: Yasuda
authors: Department of Health and Nutrition Science, Nishikyushu University, Kanzaki, Saga 842-8585, Japan.
authors: Chika
authors: C
authors: Matsuda
authors: Department of Health and Nutrition Science, Nishikyushu University, Kanzaki, Saga 842-8585, Japan.
authors: Ayumi
authors: A
authors: Ohshiro
authors: Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors: Kuniyo
authors: K
authors: Inouye
authors: Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan.
authors: Masaaki
authors: M
authors: Tabata
mesh_terms: D002392:Catechin / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003300:Copper / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D002412:Cations; D005290:Ferric Compounds; D005296:Ferrous Compounds; D003300:Copper; D002392:Catechin
keywords: CV; Catechins; ESI-MS; HPLC; Metal complexes; Oxidation