4. Glycoalkaloids & Tropane Alkaloids
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Early chemical discoveries

Unknown to the ancients, some interesting chemistry underlies the mystical properties of nightshades. Glycoalkaloids are complex organic molecules that tend towards high biological activity. (For the chemists among you, here is a structural description: “Glycoalkaloids consist of a six-ring steroid structure [aglycon)] with a sugar moiety attached to the 3-position of the first ring and a nitrogen atom in the sixth ring end of the molecule.”)1

Glycoalkaloids were first isolated from nightshade plants in the 1820s by a French apothecary and a Swiss chemist. A formulary from 1827 provides a recipe for isolating solanine, found in many nightshades and particularly potatoes. It reports that a cat and dog given small doses vomited. “The solanine has not yet been tried upon the sick, but it may be used in cases where the extract of nightshade or that of bitter sweet are indicated,” it concluded.2 (Despite their imperfections, let us give thanks for modern medical standards and clinical trials!)

tl;dr Glycoalkaloids and tropane alkaloids are complex and bioactive molecules discovered in nightshades beginning in the early 1800s. Their easy availability and action on nerve cells helped unravel the chemistry of nerve transmission, leading to a 1936 Nobel Prize.

In 1833 Philipp L. Geiger, working with Ludwig Hesse, reported isolating the psychoactive3 poisons atropine and hyoscyamine. (Chemists now understand that atropine is actually a combination of two variants of hyoscyamine.4) Poisons when used in quantity, these tropane alkaloids also proved to have medicinal value. They are used even today as medications for stimulating heart rate and as an antidote for nerve gas and some pesticide poisonings.

Atropine was first cracked from belladonna roots in 1831 by a German apothecary, but can be isolated from other nightshade plants including jimsonweed. Experimenters discovered it had a deadening effect on cells of the nervous system. It does this by chemically jamming acetylcholinesterase, the enzyme that breaks down acetylcholine. (Acetylcholine is a neurotransmitter, a chemical that allows neurons to communicate with one another. Without acetylcholinesterase there is too much of a good thing.)

After chemists mastered the challenge of producing atropine in quantity, Sir Henry Hallett Dale and Otto Loewi used it to help unravel the chemical nature of nerve transmission. This achievement won them the 1936 Nobel in Physiology or Medicine.5

1948: Discovery of Tomatine

Tomatine, the predominant glycoalkaloid found in tomatoes, was chemically isolated by scientists working at the Eastern Regional Research Center of the United States Department of Agriculture in 1948.6 Initial research noted its damping effect on the human pathogens Escherichia coli and Staphylococcus aureus. This research also noted strong anti-fungal properties.7

NEXT: James Roddick Explores Glycoalkaloids

  1. Molecular basis of glycoalkaloid induced membrane disruption []
  2. page 79, Formulary for the Preparation and Employment of Several New Remedies, 1827 edition []
  3. “Psychoactivity of atropine in normal volunteers” []
  4. “Tropane alkaloids as medicinally useful natural products and their synthetic derivatives as new drugs” []
  5. “The Chemical Transmission of Nerve Action,” Otto Loewi Nobel Lecture, December 12, 1936 []
  6. “Isolation and partial characterization of crystalline tomatine, an antibiotic agent from the tomato plant” []
  7. “Tomato glycoalkaloids: role in the plant and in the diet” []

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