111
7
alkaloids such as melanin or catecholamine and some plants enrich L-DOPA in their
leaves and bean pods (Sathiyanarayanan and Arulmozhi 2007).
L-DOPA can be converted by DOPA carboxylase to dopamine and thus increase dopamine concentrations in the central and the peripheral nervous system. This appears to be
part of a defence system since velvet beans seem to be well protected against attacks by
small mammals and insects. It was shown that larvae of the Southern armyworm show an
increased mortality when fed with either velvet seeds or L-DOPA (Rehr et al. 1973) indicating that this compound is directly involved in the protection. By contrast, the macro
algae Ulvaria obscura seems to use dopamine itself as an anti-herbivore to reduce consumption by snails and isopods (Van Alstyne et al. 2014). As observed before, some animal can overcome these defences and even use them for their own advantages. In case of
L-DOPA, the pea aphid Acyrthosiphon pisum can feed on broad beans without detrimental effects. Even more, it sequesters L-DOPA and even passes it on to the next generation.
Zhang and co-workers (2015) further suggested that it might be used to improve wound
healing and to protect against UV-A damage. Similar to caffeine it was suggested that
plants might use L-DOPA for allelopathy (Nishihara et al. 2004; Soares et al. 2012) since
they extrude the compound from the roots into the soil where it reaches high enough
concentrations to become inhibitory for plant growth.
7.6 5HT2A Receptors: Ergotamine and Mescaline
The 5HT2A receptor agonists psilocybin and ergotamine come from mushrooms and not
plants. The alkaloid psilocybin is one of the major psychoactive substances of “magic
mushrooms” such as members of the genus Psilocybe (Hofmann et al. 1959). Ergotamine,
which also binds dopamine receptors and adrenergic receptors with high affinity, is a
derivative of ergoline and part of the ergot family of alkaloids found in lower fungi (Schardl
et al. 2006). It is best known as the causal agent of ergotism, a poisoning that occurs in
humans and other mammals who consume rye grains contaminated with the fungus
Claviceps purpurea. Medicinal usage of ergot fungus began in the sixteenth century to
hasten childbirth (or induce abortion), yet dosage uncertainties discouraged the use. It
has also been employed to prevent post-partum haemorrhage (Lonitzer, 1593).
Ergotamine was first isolated from the ergot fungus by Arthur Stoll at Sandoz in 1918,
and it was in connection with his work on ergotamine that the German chemist Albert
Hofmann synthesized LSD in 1938 (Hofmann 1980). Ergotamine is not restricted to rye
grain since infection of grass seeds with endophytic fungi producing mycotoxins is quite
common (Czarnoleski et al. 2010). Ergotamine is also found in the seeds of certain dicotyledonous plants, and it is believed that in all cases it is of fungal origin (Steiner et al. 2006).
It is further believed that the formation of ergotamine and other mycotoxins might be part
of a mutual benefit situation, where the compound made by fungi protects the seeds from
pathogen infection and herbivores, while the fungus obtains nutrients from the plant.
A plant-derived secondary metabolite known to interact with the 5HT2A receptor is
the phenethylamine alkaloid mescaline (. Fig. 7.10), which is found in several members of
the Cactaceae (Poisson 1960; Crosby and McLaughlin 1973). Buttons from peyote cacti
(Lophophora williamsii) and mescal bean (Sophora secundiflora) are used by native North
Americans to brew a hallucinating drink for spiritual purposes and archaeoethnobotany
evidence suggest that this habit might have been around for at least 5500 years (El-Seedi
et al. 2005; Bruhn et al. 2002). Mescaline is a nonselective serotonin receptor agonist, inter7.6 · 5HT2A Receptors: Ergotamine and Mescaline
7
alkaloids such as melanin or catecholamine and some plants enrich L-DOPA in their
leaves and bean pods (Sathiyanarayanan and Arulmozhi 2007).
L-DOPA can be converted by DOPA carboxylase to dopamine and thus increase dopamine concentrations in the central and the peripheral nervous system. This appears to be
part of a defence system since velvet beans seem to be well protected against attacks by
small mammals and insects. It was shown that larvae of the Southern armyworm show an
increased mortality when fed with either velvet seeds or L-DOPA (Rehr et al. 1973) indicating that this compound is directly involved in the protection. By contrast, the macro
algae Ulvaria obscura seems to use dopamine itself as an anti-herbivore to reduce consumption by snails and isopods (Van Alstyne et al. 2014). As observed before, some animal can overcome these defences and even use them for their own advantages. In case of
L-DOPA, the pea aphid Acyrthosiphon pisum can feed on broad beans without detrimental effects. Even more, it sequesters L-DOPA and even passes it on to the next generation.
Zhang and co-workers (2015) further suggested that it might be used to improve wound
healing and to protect against UV-A damage. Similar to caffeine it was suggested that
plants might use L-DOPA for allelopathy (Nishihara et al. 2004; Soares et al. 2012) since
they extrude the compound from the roots into the soil where it reaches high enough
concentrations to become inhibitory for plant growth.
7.6 5HT2A Receptors: Ergotamine and Mescaline
The 5HT2A receptor agonists psilocybin and ergotamine come from mushrooms and not
plants. The alkaloid psilocybin is one of the major psychoactive substances of “magic
mushrooms” such as members of the genus Psilocybe (Hofmann et al. 1959). Ergotamine,
which also binds dopamine receptors and adrenergic receptors with high affinity, is a
derivative of ergoline and part of the ergot family of alkaloids found in lower fungi (Schardl
et al. 2006). It is best known as the causal agent of ergotism, a poisoning that occurs in
humans and other mammals who consume rye grains contaminated with the fungus
Claviceps purpurea. Medicinal usage of ergot fungus began in the sixteenth century to
hasten childbirth (or induce abortion), yet dosage uncertainties discouraged the use. It
has also been employed to prevent post-partum haemorrhage (Lonitzer, 1593).
Ergotamine was first isolated from the ergot fungus by Arthur Stoll at Sandoz in 1918,
and it was in connection with his work on ergotamine that the German chemist Albert
Hofmann synthesized LSD in 1938 (Hofmann 1980). Ergotamine is not restricted to rye
grain since infection of grass seeds with endophytic fungi producing mycotoxins is quite
common (Czarnoleski et al. 2010). Ergotamine is also found in the seeds of certain dicotyledonous plants, and it is believed that in all cases it is of fungal origin (Steiner et al. 2006).
It is further believed that the formation of ergotamine and other mycotoxins might be part
of a mutual benefit situation, where the compound made by fungi protects the seeds from
pathogen infection and herbivores, while the fungus obtains nutrients from the plant.
A plant-derived secondary metabolite known to interact with the 5HT2A receptor is
the phenethylamine alkaloid mescaline (. Fig. 7.10), which is found in several members of
the Cactaceae (Poisson 1960; Crosby and McLaughlin 1973). Buttons from peyote cacti
(Lophophora williamsii) and mescal bean (Sophora secundiflora) are used by native North
Americans to brew a hallucinating drink for spiritual purposes and archaeoethnobotany
evidence suggest that this habit might have been around for at least 5500 years (El-Seedi
et al. 2005; Bruhn et al. 2002). Mescaline is a nonselective serotonin receptor agonist, inter7.6 · 5HT2A Receptors: Ergotamine and Mescaline