What is the species name of the ergot fungus used to produce the drug ergotamine?

The species name of the ergot fungus used to produce ergotamine is Claviceps purpurea.

Claviceps purpurea is best known as the ergot fungus of rye and other grasses. It replaces a host plant’s developing grain with a hard, dark structure called a sclerotium, commonly known as ergot. These structures contain ergot alkaloids, a chemically diverse family of compounds that includes ergotamine.

Ergotamine is an ergopeptine alkaloid and a potent vasoconstrictor. It became historically important in migraine treatment, particularly after its isolation in 1918. Modern production can use selected strains grown in controlled culture rather than relying only on naturally infected rye. Research has demonstrated ergotamine biosynthesis in submerged cultures of Claviceps purpurea.

The distractors are related species but are associated with different alkaloid profiles. Claviceps paspali is known for producing lysergic-acid derivatives, while Claviceps fusiformis is associated with clavine alkaloids; Claviceps africana produces other ergot alkaloids. This is why Claviceps purpurea is the canonical answer for ergotamine, even though related fungi can make members of the broader ergot-alkaloid family. The fungus is also responsible for ergotism when contaminated grain is consumed.