title: Development of a bioassay-coupled HPLC-SPE-ttNMR platform for identification of α-glucosidase inhibitors in apple peel (Malus ×domestica Borkh.).
abstract: This work describes an analytical platform based on a high-resolution α-glucosidase inhibition assay in combination with hyphenation of high-performance liquid chromatography, solid-phase extraction, and tube-transfer nuclear magnetic resonance spectroscopy, i.e., HPLC-SPE-ttNMR/high-resolution α-glucosidase assay. The platform enables fast screening for individual α-glucosidase inhibitory analytes in complex matrices, followed by structural identification targeted these α-glucosidase inhibitors, as demonstrated by a proof-of-concept study with extract of 'Pink Lady' apple peel. A scout-separation produced a high-resolution biochromatogram and a HPLC chromatogram, which were used for pinpointing HPLC peaks displaying α-glucosidase inhibition. Active analytes were cumulatively trapped on SPE cartridges and the structures identified by (1)H NMR experiments obtained in the HPLC-SPE-ttNMR mode. (-)-Epicatechin (1), reynoutrin (3) and avicularin (4) were identified as active compounds. IC(50) of the active compounds were determined along with six structurally related compounds. Quercetin was the most potent inhibitor with an IC(50) of 8.1±0.4μM. The platform proved to be an efficient method for the identification of α-glucosidase inhibitors.
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors.forename: Jeppe S
authors.initials: JS
authors.lastname: Schmidt
authors.forename: Michael B
authors.initials: MB
authors.lastname: Lauridsen
authors.forename: Lars O
authors.initials: LO
authors.lastname: Dragsted
authors.forename: John
authors.initials: J
authors.lastname: Nielsen
authors.forename: Dan
authors.initials: D
authors.lastname: Staerk
mesh_terms: D001681:Biological Assay / Q000379:methods*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004791:Enzyme Inhibitors / Q000737:chemistry*; D005638:Fruit / Q000737:chemistry; D065089:Glycoside Hydrolase Inhibitors; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D027845:Malus / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*; D052616:Solid Phase Extraction / Q000379:methods*
chemical_list: D004791:Enzyme Inhibitors; D065089:Glycoside Hydrolase Inhibitors; D010936:Plant Extracts