197
12
It contains a tetracyclic bis-quinolizidine ring system and is formed by incorporation of
a third lysine or cadaverine molecule. Cytisine, a tricyclic quinolizidine alkaloid found in
Baptisia, Cytisus, Laburnum and Sophora species, has nicotine-like effects on the gastrointestinal tract and on the central nervous system. These plants are sometimes smoked recreationally for their stimulant effects and mild hallucinogenic properties. Cytisine is probably
formed from a tetracyclic system by loss of carbon atoms. N-methylcytisine is often found
in herbal preparations of blue cohosh, an abortifacient (from Caulophyllum thalictroides,
Berberidaceae) (Rao and Hoffman 2002; Dugoua et al. 2008). Anagyrine is a partial agonist
at NAchR and is nematicidal (Green et al. 2013). It can cause deformities and cleft palate in
cattle (“crooked calf disease”) fed on Lupinus, but not in sheep (Lee et al. 2007).
The majority of quinolizidine alkaloids are synthesized in the aerial parts of plants.
They can accumulate in seeds, sometimes being synthetized in the seeds, but often translocated to the seeds by phloem (Lee et al. 2007). During germination, their concentration
is reduced.
Lycopodium alkaloids, which are only found in plants of the families Lycopodiaceae
and Huperziaceae are probably derived from quinolizidine alkaloids and are characterized
by four six-membered rings. Huperzine A (from Huperzia serrata) acts as an inhibitor of
acetylcholine esterase and is used in the treatment of Alzheimer’s disease to increase the
levels of acetylcholine (Xing et al. 2014; Zheng et al. 2016).
Indolizidine alkaloids are characterized by fused six- and five-membered rings, with a
nitrogen atom at the ring fusion, and are formed from L-Lys via L-pipecolic acid. Typical
indolizidine alkaloids are castanospermine (from chestnut, Castanospermum austral,
Fabaceae), an inhibitor of some glucosidase enzymes, and swainsonine (from Swainsona
canescens, Astragalus sp., Fabaceae), which is actually not produced by the plant but by
fungal endophytes (Ren et al. 2017). Swainsonine can cause poisoning in livestock. It is an
inhibitor of the Golgi alpha-mannosidase II, thus inducing accumulation of mannose oligosaccharides. The resulting lysosomal storage disease affects many reproductive functions
in cattle.
12.11 Steroidal Alkaloids (From Steroids Derived
from the MVA Pathway)
Steroidal alkaloids are based on a C 27 cholestane skeleton and include, for instance, solasodine and tomatidine, two nitrogen-containing analogues of steroids. Cholesterol, produced through the cytosolic MVA pathway, is the precursor in their biosynthesis (see
7 Sect. 10.6 in 7 Chap. 10). Similar to saponins they are also present in plants as glycosides. They often occur in Solanaceae, solasonine in several Solanum species and tomatine
in tomato (Solanum lycopersicum). The toxic and bitter α-solanine, the glycoside of solanidine, can also be found in potatoes (Solanum tuberosum) and is mainly accumulating in
green tissues (but also in green parts of the potato tuber). These compounds inhibit acetylcholine esterase (AChE) that is required to hydrolyse and inactivate the neurotransmitter
acetylcholine. Therefore, some of these substances from the Solanaceae are also discussed
as bioinsecticides (Chowanski et al. 2016).
Cyclopamine isolated from corn lily (Veratrum californicum, Melanthiaceae) antagonizes a signalling pathway that is overactive in basal cell carcinoma and other cancers.
Veratridine from Liliaceae prevents the inactivation of voltage-gated sodium ion channels
and can be used as an insecticide.
12.11 · Steroidal Alkaloids (From Steroids Derived from the MVA Pathway)
12
It contains a tetracyclic bis-quinolizidine ring system and is formed by incorporation of
a third lysine or cadaverine molecule. Cytisine, a tricyclic quinolizidine alkaloid found in
Baptisia, Cytisus, Laburnum and Sophora species, has nicotine-like effects on the gastrointestinal tract and on the central nervous system. These plants are sometimes smoked recreationally for their stimulant effects and mild hallucinogenic properties. Cytisine is probably
formed from a tetracyclic system by loss of carbon atoms. N-methylcytisine is often found
in herbal preparations of blue cohosh, an abortifacient (from Caulophyllum thalictroides,
Berberidaceae) (Rao and Hoffman 2002; Dugoua et al. 2008). Anagyrine is a partial agonist
at NAchR and is nematicidal (Green et al. 2013). It can cause deformities and cleft palate in
cattle (“crooked calf disease”) fed on Lupinus, but not in sheep (Lee et al. 2007).
The majority of quinolizidine alkaloids are synthesized in the aerial parts of plants.
They can accumulate in seeds, sometimes being synthetized in the seeds, but often translocated to the seeds by phloem (Lee et al. 2007). During germination, their concentration
is reduced.
Lycopodium alkaloids, which are only found in plants of the families Lycopodiaceae
and Huperziaceae are probably derived from quinolizidine alkaloids and are characterized
by four six-membered rings. Huperzine A (from Huperzia serrata) acts as an inhibitor of
acetylcholine esterase and is used in the treatment of Alzheimer’s disease to increase the
levels of acetylcholine (Xing et al. 2014; Zheng et al. 2016).
Indolizidine alkaloids are characterized by fused six- and five-membered rings, with a
nitrogen atom at the ring fusion, and are formed from L-Lys via L-pipecolic acid. Typical
indolizidine alkaloids are castanospermine (from chestnut, Castanospermum austral,
Fabaceae), an inhibitor of some glucosidase enzymes, and swainsonine (from Swainsona
canescens, Astragalus sp., Fabaceae), which is actually not produced by the plant but by
fungal endophytes (Ren et al. 2017). Swainsonine can cause poisoning in livestock. It is an
inhibitor of the Golgi alpha-mannosidase II, thus inducing accumulation of mannose oligosaccharides. The resulting lysosomal storage disease affects many reproductive functions
in cattle.
12.11 Steroidal Alkaloids (From Steroids Derived
from the MVA Pathway)
Steroidal alkaloids are based on a C 27 cholestane skeleton and include, for instance, solasodine and tomatidine, two nitrogen-containing analogues of steroids. Cholesterol, produced through the cytosolic MVA pathway, is the precursor in their biosynthesis (see
7 Sect. 10.6 in 7 Chap. 10). Similar to saponins they are also present in plants as glycosides. They often occur in Solanaceae, solasonine in several Solanum species and tomatine
in tomato (Solanum lycopersicum). The toxic and bitter α-solanine, the glycoside of solanidine, can also be found in potatoes (Solanum tuberosum) and is mainly accumulating in
green tissues (but also in green parts of the potato tuber). These compounds inhibit acetylcholine esterase (AChE) that is required to hydrolyse and inactivate the neurotransmitter
acetylcholine. Therefore, some of these substances from the Solanaceae are also discussed
as bioinsecticides (Chowanski et al. 2016).
Cyclopamine isolated from corn lily (Veratrum californicum, Melanthiaceae) antagonizes a signalling pathway that is overactive in basal cell carcinoma and other cancers.
Veratridine from Liliaceae prevents the inactivation of voltage-gated sodium ion channels
and can be used as an insecticide.
12.11 · Steroidal Alkaloids (From Steroids Derived from the MVA Pathway)