Integrated Electrophysiological and Structural Evidence Identifies Dehydroelsholtzia Ketone and Elsholtzia Ketone as the Principal Bioactive Constituents of Elsholtzia ciliata Essential Oil

<jats:p>&lt;b&gt;Background and Purpose&lt;/b&gt; Previous studies showed that the ketone-rich chemotype of &lt;i&gt;Elsholtzia ciliata&lt;/i&gt; essential oil (EO) exhibits a characteristic class IB-like cardiac electrophysiological profile. However, the contribution of its two major constituents, dehydroelsholtzia ketone (DEK) and elsholtzia ketone (EK), remained unknown. This study investigated whether these ketones account for the characteristic electrophysiological activity of the complete EO. &lt;b&gt;Experimental Approach&lt;/b&gt; Electrophysiological effects of DEK and EK were investigated in Langendorff-perfused rabbit hearts using intracellular microelectrode recordings. Concentration-dependent changes in activation time, maximal action potential upstroke velocity (dV/dt&lt;sub&gt;max&lt;/sub&gt;) and action potential duration (APD) were quantified. Use-dependent effects were assessed during rapid pacing, ventricular activation by optical mapping, and structural compatibility with human Na&lt;sub&gt;V&lt;/sub&gt;1.5 by molecular docking. &lt;b&gt;Key Results&lt;/b&gt; Both ketones reproduced the principal electrophysiological effects previously observed with the complete EO, producing concentration-dependent slowing of ventricular activation, depression of dV/dt&lt;sub&gt;max&lt;/sub&gt; and shortening of APD. EK was approximately two-fold more potent than DEK, whereas DEK is the predominant ketone in the EO. Both compounds exhibited pronounced use-dependent depression of dV/dt&lt;sub&gt;max&lt;/sub&gt;. Optical mapping confirmed homogeneous slowing of ventricular activation, and molecular docking supported compatibility of both ketones with the established class I antiarrhythmic drug-binding cavity of human Na&lt;sub&gt;V&lt;/sub&gt;1.5. &lt;b&gt;Conclusions and Implications&lt;/b&gt; DEK and EK are the principal determinants of the characteristic cardiac electrophysiological activity of ketone-rich &lt;i&gt;Elsholtzia ciliata&lt;/i&gt; EO. These findings provide a mechanistic basis for chemical standardization of this chemotype and identify both ketones as promising lead structures for future sodium channel-modulating drugs.</jats:p>