19 June 2017

(S)-(-)-Hyoscyamine - a tropane alkaloid

Natural toxin

Alkaloids are very important phytotoxins occurring in plants all over the world. (S)-(-)-Hyoscyamine is a major tropane alkaloid in Solanaceae and is due to the strong biological activity well investigated.

(S)-(-)-Hyoscyamine. Click image for 3D structure

(S)-(-)-Hyoscyamine (CAS 101-31-5) is a major toxin in several plant species of the nightshade family (Solanaceae) including the in Europe growing Atropa, Brugmansia, Datura, Hyoscyamus and Mandragora genera. In plants, hyoscyamine appears in a mixture of tropane alkaloids and together with scopolamine accounts for the majority of the toxic effect. The alkaloid concentration pattern varies strongly within species, seasons, geographic locations and plant parts. Often the racemic mixture Atropine is described, in which (-)-hyoscyamine is the toxicological relevant form with a 10-20 more effective biological activity compared with the enantiomer.

Hyoscyamine acts as antagonist of acetylcholine receptors blocking the activity of the neurotransmitter acetylcholine and, therefore, leads to effects on the heart rate, respiration and the central nervous system. Hyoscyamine poisonings occur through unintended ingestions in cases of contaminated food or botanical misidentification, but also through intentional ingestion. At low concentrations hyoscyamine has medicinal importance as therapeutic agent and in alternative medicines, but hyoscyamine containing plants are also abused. In the past Mandragora officinarum was used as magical ritual plant and Atropa belladonna was applied to dilate the pupils for aesthetic reasons. Nowadays, Datura species are due to the hallucinogenic effect the most common plants for abuse in Switzerland.

Numerous methods are available to detect hyoscyamine in plant material and biological samples. The method of choice for concentration determination is liquid chromatography (LC) coupled to mass spectrometry (MS), favorable LC-MS/MS. Hyoscyamine is a polar compound (measured logKow 1.83, EPISuite logKow 1.91) and assumed to at least partly leach to the surface water. Unfortunately, the occurrence in the environment is not reported but should be investigated due to the toxicity and wide-spread growth of the tropane alkaloid containing plants.



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