Chlorahololides C–F: a new class of potent and selective potassium channel blockers from Chloranthus holostegius

Four unusually fused polycyclic sesquiterpenoid dimers, chlorahololides C–F (1–4), were isolated from the whole plant of Chloranthus holostegius. Their structures and absolute configurations were established by spectroscopic methods, including 2D NMR and CD spectra. Chlorahololides C–F (1–4) exerted potent and selective inhibition on the delayed rectifier (IK) K+ current with the IC50 values of 3.6±10.1, 2.7±0.3, 27.5±5.1 and 57.5±6.1 μM, respectively.