Hemlock alkaloids from Socrates to poison aloes

The toxicity of hemlock (Conium maculatum L.) is due to a group of simple piperidine alkaloids represented by coniine and γ-coniceine. Levels of the various compounds depend very much on variety, environmental conditions and provenance of the plants. Surprisingly the alkaloids turned up in a quite unrelated genus, Aloe but only in a very few species, the rest not being thought of as poisonous. They have also been found in other unrelated plants. The compounds are neurotoxins and the acute effect is death by respiratory failure. Chronic non-lethal ingestion by pregnant livestock leads to foetal malformations. It has been suggested that they may function in respiratory dinucleotides. Many aspects of their physiology and biochemistry invite new research.