title: The photobase generator nifedipine as a novel matrix for the detection of polyphenols in matrix-assisted laser desorption/ionization mass spectrometry.
abstract: Matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) is widely used for the detection and analysis of ionizable compounds. However, the method has less potential for the analysis of neutral compounds, such as polyphenols, owing to their lack of favorable proton-attachment or -removal groups. In this study, we reported for the first time that nifedipine (2,6-dimethyl-3,5-dicarbomethoxy-4-(2-nitrophenyl)-1,4-dihydropyridine), which is a strong photobase generator commonly used in polymerization, can abstract protons from neutral compounds in negative mode-MALDI experiments. When nifedipine (5 mg/ml) was used as a matrix reagent, the limit of detection (LOD) for epigallocatechin-3-O-gallate (EGCG) was determined to be 100 fmol/spot, which constitutes >50-fold improvement compared to the LOD obtained when trans-3-indoleacrylic acid, a matrix reagent previously reported for polyphenol detection, was used. Of the dihydropyridines investigated, only nifedipine facilitated the detection of EGCG, suggesting that the nitrosophenyl pyridine derivative of nifedipine formed by photoreduction under laser irradiation at 355 nm plays a crucial role in detecting polyphenols in negative mode. Reduced MS detection of 5-O-methylnaringenin indicated that nifedipine may preferably remove a proton from the 5-position OH group in the A ring of the flavonoid skeleton. The significant MS detection by nifedipine was extensively observed for polyphenols including flavones, flavonones, chalcones, stilbenoids and phenolic acids. In conclusion, nifedipine can act as a novel matrix for improving polyphenol detection by MALDI-MS in negative mode. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Fukuoka, 812-8581, Japan.
authors.forename: Huu-Nghi
authors.initials: HN
authors.lastname: Nguyen
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Fukuoka, 812-8581, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Fukuoka, 812-8581, Japan.
authors.forename: Genki
authors.initials: G
authors.lastname: Komabayashi
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Fukuoka, 812-8581, Japan. tmatsui@agr.kyushu-u.ac.jp.
authors.forename: Toshiro
authors.initials: T
authors.lastname: Matsui
mesh_terms: D002392:Catechin / Q000031:analogs & derivatives / Q000032:analysis; D004095:Dihydropyridines / Q000737:chemistry; D007211:Indoles / Q000737:chemistry; D057230:Limit of Detection; D009543:Nifedipine / Q000737:chemistry*; D055668:Photochemical Processes; D058105:Polymerization; D059808:Polyphenols / Q000032:analysis*; D011522:Protons; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D004095:Dihydropyridines; D007211:Indoles; D059808:Polyphenols; D011522:Protons; C001446:indoleacrylic acid; D002392:Catechin; C045651:epigallocatechin gallate; D009543:Nifedipine
keywords: MALDI; matrix reagent; nifedipine; photobase generator; polyphenols