Investigation of the active antiarrhythmic components of the Multi-herbal Medicine Xin Su Ning Yu-ling Ma1, Taiyi Wang1, Robert Wilkins1, Clive Ellory1, Carolyn Carr1 Mao Peng2 and Jian-Dong Jiang2 Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford UK1 Shaanxi Momentum Pharmaceutical Co., Shaanxi China2 INTRODUCTION A previous study showed that Xin Su Ning (XSN), a multi-herbal antiarrhythmic Chinese medicine prolongs action potential duration (APD), a class III antiarrhythmic characteristic1. Liensinine, one of the components in XSN, showed APD prolongation with a different repolarisation profile compared with XSN. Figure 1: Herbal Medicine used in XSN C Group Herbals A & B Group herbals Filtering Procedures & Discard Solid Parts Extraction with Water Mixing Extracts from all the herbs Extraction with 60% & 70% Ethanol Freeze – dry the Extracts Powder Form of XSN Preparation Semi-liquid form of Extracts Concentrating the Extracts AIM In this study we aim to explore further the antiarrhythmic mechanism of XSN and to identify the main active component(s) that may, or partially, be responsible for the action potential prolongation of XSN. METHODS Experimental Medicine preparation: Figure 1 outlines the procedure of the extraction of the experimental XSN preparation. It was prepared by ethanol extraction for parts of the herbs and water extraction for the rest of the herbs. Cellular electrophysiology: Ventricular myocytes were isolated from the hearts of adult Wistar rats. The cells were continuously superfused at room temperature with a solution of the following composition (in mM): NaCl, 112; KCl, 5.4; MgC2 1.0; CaCl2 ,1.0; NaH2PO4, 1.0; HEPES, 5.0; Glucose 10; NaHCO2, 24; gassed with 95% O2/5%CO2; pH 7.4. The whole-cell patch-clamp technique was used to measure action potential as previously described2. The pipette solution contained (in mM): KCl,140; MgCl2 1.0; EGTA, 5; HEPES, 10; ATP, 2. XSN and Lliensinine were dissolved in the extracellular solution and perfused to the cells. Figure 2: a b c RESULTS Figure 1: Diagram of the procedure of Xing Su Ning preparation. Figure 2: The effect of XSN on the action potential of cardiac ventricular myocyte. XSN prolonged action potential duration in a dose-dependent manner. Panel a) shows the superimposed AP at control, XSN at different concentrations as the key indicate, and panel b) shows the concentration dependent effect of XSN on action potential. Panel c) shows the effect of XSN at various concentrations on APD plotted against time. APD was measured at 90% re-polarization of the action potential. Figure 3: The effect of XSN on IK of cardiac myocytes. The upper panel shows the voltage clamp protocol and the current traces recorded at control, in the presence of XSN and recovery as the keys indicate. The lower panel shows the current–voltage relationship plots at control and in the presence of XSN. Figure 4: The effect of XSN and liensinine on action potential duration. Panel a) shows the effect of XSN at concentration of 0.4mg/ml; panel b) shows the effect of liensinine at concentration of 10µM on action potential and panel c) shows the effect of liensinine on INa. The action potentials in panel A & B were recorded in one myocyte in a continuous experiment. Figure 3: Figure 4: a b c CONCLUSION XSN, a patented multi-herbal Chinese medicine, has been sold in China for more than 10 years to treat ventricular arrhythmia without adverse reactions being reported. Liensinine, one of the hundreds components in XSN induced APD prolongation with a different feature compared with XSN; this result opens up a wide range of research of XSN. Studying the antiarrhythmic mechanism of XSN may enrich our knowledge of multi-component antiarrhythmic actions of drugs.  ACKNOWLEDGEMENT The project was sponsored by Momentum Pharmaceutical Co. Ltd. Shaanxi China. We are grateful for the support gained from Professors P. Robbins, R. Vaughan-Jones, K. Clarke and Dr M Richards in the Department of Physiology, Anatomy and Genetics, University of Oxford.   References 1. Ma Y-L et al. (2015). http://www.ascept-bps2015.com/wp-content/uploads/2014/04/ASCEPT-BPS-Poster-programme-and-abstracts. 2. Ma Y-L at al. (2006). European Journal of Pharmacology. 545:87-92 Table 1 Effect of XSN and liensinine on APD50 & APD90   APD50 (Normalized) APD90(Normalized) APA (Normalized) Xin Su Ning (0.4mg/ml) 1.34±0.06 (n=5)* 1.224±0.03 0.96±0.02 (n=5) Liensinine (10µM) 0.96±0.03 (n=4) 1.35±0.04 (n=4)* 0.90±0.07 *P<0.05 compared with control as 1