Cymarin

Cymarin is a cardenolide glycoside, a type of cardiac glycoside, found in various plant species, notably Apocynum cannabinum (dogbane) and Strophanthus species. Chemically, it consists of the steroid aglycone cymarigenin linked to the sugar cymarose.

Cymarin acts as a potent inhibitor of the Na+/K+-ATPase pump, an enzyme critical for maintaining the electrochemical gradient across cell membranes, particularly in heart cells. By inhibiting this pump, cymarin increases intracellular sodium and calcium levels, leading to increased cardiac contractility. This effect makes it a cardiotonic agent.

Historically, cymarin and other cardiac glycosides have been used in medicine to treat congestive heart failure and certain types of arrhythmias. However, due to their narrow therapeutic window (the difference between a therapeutic dose and a toxic dose) and the availability of safer alternatives, their use has declined significantly in modern medicine.

Cymarin is highly toxic and ingestion can cause serious adverse effects including nausea, vomiting, irregular heartbeat, seizures, and even death. Exposure can occur through accidental ingestion of plants containing the compound.