Oenanthotoxin is a toxin extracted from hemlock water dropwort (Oenanthe crocata) and other plants of the genus Oenanthe. It is a central nervous system poison, and acts as a noncompetitive gamma-aminobutyric acid (GABA) antagonist. A case has been made for the presence of this toxin in local Oenanthe species playing a causative role in euthanasia in ancient Sardinia. It was crystallized in 1949 by Clarke and co-workers. It is structurally closely related to the toxins cicutoxin and carotatoxin. Oenanthotoxin is a C17 polyacetylene isomer of cicutoxin. Oenanthotoxin is a toxin extracted from hemlock water dropwort (Oenanthe crocata) and other plants of the genus Oenanthe. It is a central nervous system poison, and acts as a noncompetitive gamma-aminobutyric acid (GABA) antagonist. A case has been made for the presence of this toxin in local Oenanthe species playing a causative role in euthanasia in ancient Sardinia. It was crystallized in 1949 by Clarke and co-workers. It is structurally closely related to the toxins cicutoxin and carotatoxin. Oenanthotoxin is a C17 polyacetylene isomer of cicutoxin. Oenanthotoxin concentration in plants is dependent on seasonal changes and geographical location, the most is present during late winter and early spring. Contrary to most poisonous plants that contain bitter tastes or burning sensations, the water dropwort has a rather sweet and pleasant taste and odor. Water dropwort is characterized by a yellow liquid that changes color due to air exposure. The roots are the most toxic part, although the entire plant contains poisonous properties. The discovery and use of plants containing oenanthotoxin predates Socrates and Homer and its first use as a poison is thought to have been implemented between 1800 BCE and 800 BCE in Pre-Roman Sardinia. In Ancient Sardinia, it was considered to be a humane form of euthanasia. Elderly people who were unable to care for themselves were given water dropwort and dropped from a high rock to ensure death. It is also believed that Socrates ingested the plant when executed. A common symptom of oenanthotoxin is risus sardonicus, better known as the Sardonic Grin, coined by Homer in the 8th century BCE, due to the victim's rigid smile after ingestion. Furthermore, as a muscle relaxant, it is believed to have cosmetic botox-like properties in small amounts.