Evaluation of the effect of deacetyl-tanghinin on cardiac activity

Desacetyl-tanghinin is a cardiac glycoside isolated from Tanghinia venenifera Poir. (Apocynaceae). The present study aimed to evaluate its effects on cardiac activity using the Langendorff retroperfusion technique on an experimentally failing isolated frog heart. The compound was introduced into the perfusion system, and its effects on cardiac output, contractile force, heart rate, and diastolic filling time were assessed. Its influence on cardiac electrical activity was also investigated by recording the electrocardiogram (ECG) using lead II.

The results showed that, at concentrations ranging from 1 × 10⁻⁵ to 7.96 × 10⁻⁵ M, desacetyl-tanghinin increased the cardiac output from 27 ± 0.577 mL/min to 83.4 ± 1.154 mL/min, force of contraction from baseline to 177.15 ± 1.01 %, with a pD₂ value of 5.336. The same concentration range decreased heart rate from 55 ± 0.06 to 28.99 beats/min, while it increased diastolic duration from 0.05 ± 0.02 to 0.153 ± 0.005 s (p < 0.05). These findings indicate a positive inotropic and lusitropic effect associated with a negative chronotropic effect.

The ECG recording shows atrioventricular block at 2.89 ± 0.17 mg/kg, extrasystoles at 3.41 ± 0.148 mg/kg, ventricular fibrillation at 5 ± 0.24 mg/kg, and cardiac arrest at 6.85 ± 0.37 mg/kg.

These results demonstrate that desacetyl-tanghinin increases heart output of failing isolated frog heart, exhibits positive inotropic and lusitropic, and negative chronotropic effects, which are characteristic pharmacological properties of cardiotonic glycosides.