title: HERG channel inhibitors in extracts of Coptidis rhizoma.
abstract: Inhibition of the hERG channel delays repolarization and prolongs the QT interval and cardiac action potential which can lead to sudden death. Several drugs have been withdrawn from the market due to hERG channel inhibition. In the search of hERG channel inhibitors of natural origin, we established an HPLC-based profiling approach which combines HPLC-microfractionation and bioactivity testing on Xenopus laevis oocytes. The methanolic extract of the TCM herbal drug Coptidis rhizoma (Coptis chinensis Franch., Ranunculaceae) reduced the peak tail hERG current by 31.7 ± 2.0% at 100 µg/mL. HPLC-based activity profiling pointed towards berberine as the active constituent. However, hERG inhibition by 100 µM of a reference sample of berberine (16.3 ± 1.6%) was less pronounced than previously reported. Subsequent LC-PDA-MS analysis showed that berberine collected by microfractionation of the Coptis extract had been, in part, transformed to active dihydroberberine. Formic acid added to the HPLC mobile phase to reduce peak tailing of protoberberine alkaloids acted as a reducing reagent according to the mechanism of the Leuckart-Wallach reaction. Among other structurally related protoberberines tested, dihydroberberine (30.1 ± 10.1% at 100 µM) was the most potent hERG inhibitor.
authors.affiliation: Division of Pharmaceutical Biology, University of Basel, Basel, Switzerland.
authors.forename: Anja
authors.initials: A
authors.lastname: Schramm
authors.forename: Igor
authors.initials: I
authors.lastname: Baburin
authors.forename: Steffen
authors.initials: S
authors.lastname: Hering
authors.forename: Matthias
authors.initials: M
authors.lastname: Hamburger
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D039323:Coptis / Q000737:chemistry*; D000089042:Coptis chinensis; D004365:Drugs, Chinese Herbal / Q000737:chemistry* / Q000494:pharmacology*; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors*; D006801:Humans; D018408:Patch-Clamp Techniques; D014982:Xenopus laevis
chemical_list: D004365:Drugs, Chinese Herbal; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C107393:Coptidis rhizoma extract