212
13
flowers of zonal geranium (Pelargonium, Geraniaceae). It is responsible for causing paralysis in some beetles.
L-canavanine is a structural analogue of L-arginine and a plant-derived insecticide,
detected by the gustatory receptor (GR), a G-protein-coupled receptor of insects, to avoid
intoxication. L-canavanine is occurring in several Fabaceae and is considered as a strong
allelochemical, which is often stored in seeds. Its biosynthesis involves the conversion of
L-canavaninosuccinic acid to L-canavanine and fumaric acid
Caramboxin is similar to phenylalanine with additions at the phenol ring. It acts as a
neurotoxin, especially the caramboxin from star fruit (Syn. carambola, Averrhoa carambola, Oxalidaceae). Patients with kidney disease can accumulate caramboxin after digestion of bananas, oranges, tomatoes, nuts, broccoli, beans and star fruit, and the neurotoxin
can enter the brain, where it overactivates glutamate receptors in the brain leading to hiccups, vomiting, weakness, mental confusion and psychomotor agitation and to unusually
long- lasting epileptic seizures, coma and death (Garcia-Cairasco et al. 2013).
13.5 Acetylcholine
The neurotransmitter acetylcholine is mainly known from humans and animals, but it is
also present in many plant species as well as in bacteria and fungi (Tretyn and Kendrick
1991). The biosynthesis in plants seems similar to the production pathway in animals,
as choline acetyltransferase, which participates in acetylcholine synthesis from its precursors, choline and acetyl-CoA, and other corresponding enzymes (choline acetyltransferase, and the acetylcholine degrading enzyme, choline esterase) have been found in
plants. The synthesis seems to take place mainly in young leaves. High concentrations of
acetylcholine have been found in Urtica dioica (stinging nettle, Urticaceae) and related
species but also in Viscum album (mistletoe, Santalaceae) and Digitalis species (foxglove,
Plantaginaceae). In the stinging hair of nettles, acetylcholine can be found besides formic
acid and histamine (Otles and Yalcin 2012); all are probably contributing to the stinging
sensation.
References
Aza-Gonzalez C, Nunez-Palenius HG, Ochoa-Alejo N (2011) Molecular biology of capsaicinoid biosynthesis
in chili pepper (Capsicum spp). Plant Cell Rep 30:695–706. https://doi.org/10.1007/s00299-0100968- 8
Berger M, Chen Y, Bampali K, Ernst M, Maulide N (2018) Expeditious synthesis of polyacetylenic water
hemlock toxins and their effects on the major GABAA receptor isoform. Chem Commun (Camb)
54:2008–2011. https://doi.org/10.1039/c7cc09801d
Take-Home Messages
5 The best-known polyketide is Δ9-tetrahydrocannabinol (THC) from Cannabis
sativa.
5 Fatty acid-derived metabolites are polyacetylenes (such as falcarinol and cicutoxin), N-acylethanolamines, alkylamides (such as capsaicin) and coniine.
5 Non-protein amino acids can interfere with human receptors.
Chapter 13 · Minor Groups of Secondary Metabolites
13
flowers of zonal geranium (Pelargonium, Geraniaceae). It is responsible for causing paralysis in some beetles.
L-canavanine is a structural analogue of L-arginine and a plant-derived insecticide,
detected by the gustatory receptor (GR), a G-protein-coupled receptor of insects, to avoid
intoxication. L-canavanine is occurring in several Fabaceae and is considered as a strong
allelochemical, which is often stored in seeds. Its biosynthesis involves the conversion of
L-canavaninosuccinic acid to L-canavanine and fumaric acid
Caramboxin is similar to phenylalanine with additions at the phenol ring. It acts as a
neurotoxin, especially the caramboxin from star fruit (Syn. carambola, Averrhoa carambola, Oxalidaceae). Patients with kidney disease can accumulate caramboxin after digestion of bananas, oranges, tomatoes, nuts, broccoli, beans and star fruit, and the neurotoxin
can enter the brain, where it overactivates glutamate receptors in the brain leading to hiccups, vomiting, weakness, mental confusion and psychomotor agitation and to unusually
long- lasting epileptic seizures, coma and death (Garcia-Cairasco et al. 2013).
13.5 Acetylcholine
The neurotransmitter acetylcholine is mainly known from humans and animals, but it is
also present in many plant species as well as in bacteria and fungi (Tretyn and Kendrick
1991). The biosynthesis in plants seems similar to the production pathway in animals,
as choline acetyltransferase, which participates in acetylcholine synthesis from its precursors, choline and acetyl-CoA, and other corresponding enzymes (choline acetyltransferase, and the acetylcholine degrading enzyme, choline esterase) have been found in
plants. The synthesis seems to take place mainly in young leaves. High concentrations of
acetylcholine have been found in Urtica dioica (stinging nettle, Urticaceae) and related
species but also in Viscum album (mistletoe, Santalaceae) and Digitalis species (foxglove,
Plantaginaceae). In the stinging hair of nettles, acetylcholine can be found besides formic
acid and histamine (Otles and Yalcin 2012); all are probably contributing to the stinging
sensation.
References
Aza-Gonzalez C, Nunez-Palenius HG, Ochoa-Alejo N (2011) Molecular biology of capsaicinoid biosynthesis
in chili pepper (Capsicum spp). Plant Cell Rep 30:695–706. https://doi.org/10.1007/s00299-0100968- 8
Berger M, Chen Y, Bampali K, Ernst M, Maulide N (2018) Expeditious synthesis of polyacetylenic water
hemlock toxins and their effects on the major GABAA receptor isoform. Chem Commun (Camb)
54:2008–2011. https://doi.org/10.1039/c7cc09801d
Take-Home Messages
5 The best-known polyketide is Δ9-tetrahydrocannabinol (THC) from Cannabis
sativa.
5 Fatty acid-derived metabolites are polyacetylenes (such as falcarinol and cicutoxin), N-acylethanolamines, alkylamides (such as capsaicin) and coniine.
5 Non-protein amino acids can interfere with human receptors.
Chapter 13 · Minor Groups of Secondary Metabolites