Planta Med 2013; 79 - PJ21
DOI: 10.1055/s-0033-1352225

Inhibition of GIRK channels by extract of Polygonum persicaria and isolation of new flavonoids

I Lajter 1, A Vasas 1, P Orvos 2, L Tálosi 2, P Forgo 1, Z Béni 3, J Hohmann 1
  • 1University of Szeged, Institute of Pharmacognosy, Szeged, 6720, Hungary
  • 2Rytmion Ltd., Szeged, 6727, Hungary
  • 3Gedeon Richter Plc., Budapest, 1475, Hungary

Polygonum persicaria L. is a morphologically extremely variable perennial plant, naturalized in various parts of the world. Previous phytochemical studies revealed the presence of stilbenes, flavonoids and phenolic acids in the plant. In vitro pharmacological studies demonstrated its antibacterial, antifungal, insecticidal and anti-inflammatory activities.

The aim of the present work was the study of G protein-activated inwardly rectifying K+ channel (GIRK) inhibitory activity of P. persicaria. The CHCl3 extract of the plant exhibited high GIRK channel inhibitory activity at 0.1 mg/mL concentration. In the preparative experiment, the plant material was extracted with MeOH. The MeOH extract was subjected to solvent-solvent partition, affording n-hexane, CHCl3 and aqueous extracts. The CHCl3 extract was fractionated by VLC on RP-silica gel, and fractions obtained here were evaluated for GIRK modulatory activity. The most active fractions were subjected then to RP-HPLC, affording the isolation of the main compounds and a mixture containing the minor constituents. The pure compounds were identified by means of UV, HRMS and NMR spectroscopy as a new flavon (5,3',4',5'-tetramethoxy-6,7-methylenedioxyflavon) and three new flavonols (3-O-senecioyl-isorhamnetin; 3-O-angeloyl-isorhamnetin; 3,5,3',4',5'-pentamethoxy-6,7-methylenedioxyflavon). The isolated compounds were tested for GIRK inhibitory activity and found that neither separated, nor combined application of compounds modified the GIRK channel activity. However, a marked GIRK current inhibiting effect could be detected using the HPLC eluates containing the minor compounds. These results indicate the presence of electrophysiologically active agents among the minor compounds.

Acknowledgements: This work was supported by grant OTKA PD101432 and the European Union and co-funded by the European Social Fund TÁMOP-4.2.2/B-10/1 – 2010 – 0012 and TÁMOP -4.2.2.A-11/1/KONV-2012 – 0035.