Conjugated diynes

Diacetylene (also known as butadiyne) is the organic compound with the formula or . It is the simplest compound containing two triple bonds. It is first in the series of polyynes, which are of theoretical but not of practical interest.

Cicutoxin is a naturally-occurring poisonous chemical compound produced by several plants from the family Apiaceae including water hemlock (Cicuta species) and water dropwort (Oenanthe crocata). The compound contains polyene, polyyne, and alcohol functional groups and is a structural isomer of oenanthotoxin (also found in water dropwort) and bupleurotoxin (found in Bupleurum longiradiatum). All of these belong to the C17-polyacetylenes chemical class.

Falcarinol (also known as carotatoxin or panaxynol) is a natural pesticide and fatty alcohol found in carrots (Daucus carota), Panax ginseng and ivy. In carrots, it occurs in a concentration of approximately 2 mg/kg. As a toxin, it protects roots from fungal diseases, such as liquorice rot that causes black spots on the roots during storage. The compound is sensitive to light and heat.

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 antagonist of the neurotransmitter gamma-aminobutyric acid. 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.

Panaxytriol is an unsaturated fatty alcohol found in ginseng.

Falcarindiol is a polyyne found in carrot roots which has antifungal activity. Falcarindiol is the main compound responsible for bitterness in carrots. Falcarindiol and other falcarindiol-type polyacetylenes are also found in many other plants of the family Apiaceae, including some commonly used seasonings such as dill and parsley.

Capillin is a toxic naturally occurring organic compound with the chemical formula . The structure contains acetophenone and a polyyne (pentadiynyl) portion, conjugated together as an ynone.