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Molecules 2017, 22(11), 1962; doi:10.3390/molecules22111962

The killer of Socrates: Coniine and Related Alkaloids in the Plant Kingdom

VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, 02044 Espoo, Finland
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Received: 27 October 2017 / Revised: 10 November 2017 / Accepted: 12 November 2017 / Published: 14 November 2017
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Abstract

Coniine, a polyketide-derived alkaloid, is poisonous to humans and animals. It is a nicotinic acetylcholine receptor antagonist, which leads to inhibition of the nervous system, eventually causing death by suffocation in mammals. Coniine’s most famous victim is Socrates who was sentenced to death by poison chalice containing poison hemlock in 399 BC. In chemistry, coniine holds two historical records: It is the first alkaloid the chemical structure of which was established (in 1881), and that was chemically synthesized (in 1886). In plants, coniine and twelve closely related alkaloids are known from poison hemlock (Conium maculatum L.), and several Sarracenia and Aloe species. Recent work confirmed its biosynthetic polyketide origin. Biosynthesis commences by carbon backbone formation from butyryl-CoA and two malonyl-CoA building blocks catalyzed by polyketide synthase. A transamination reaction incorporates nitrogen from l-alanine and non-enzymatic cyclization leads to γ-coniceine, the first hemlock alkaloid in the pathway. Ultimately, reduction of γ-coniceine to coniine is facilitated by NADPH-dependent γ-coniceine reductase. Although coniine is notorious for its toxicity, there is no consensus on its ecological roles, especially in the carnivorous pitcher plants where it occurs. Lately there has been renewed interest in coniine’s medical uses particularly for pain relief without an addictive side effect. View Full-Text
Keywords: Aloe; alkaloids; coniine; poison hemlock (Conium maculatum L.); polyketides; Sarracenia; secondary metabolism; Socrates Aloe; alkaloids; coniine; poison hemlock (Conium maculatum L.); polyketides; Sarracenia; secondary metabolism; Socrates
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Hotti, H.; Rischer, H. The killer of Socrates: Coniine and Related Alkaloids in the Plant Kingdom. Molecules 2017, 22, 1962.

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