References

10 Neurotransmitters, Neuroregulators and Neurotoxins in Plants 143
hallucinogenic plants such as Iboga (Tabernathe iboga), Yopo (Andenanthera
perigrina), Caapi (Banisteriopsis caapi), Angel’s trumpet (Brugmansia
sp.), Peyote (Lophorora williamsii) andEbena(Virola theiodora). Still
others exploit the capacity for manipulation of brain metabolism by plants
such as marijuana (Cannabis sativa), morphine (Papaver somniferum)and
cocaine (Erythroxylon coca).
The examination of even the commonest medicinal plants can reveal
surprising chemical diversity. The efficacy of St. John’s wort (Hypericum
perforatum L.) for treatment of human ailments has a long history, perhaps
beginning with the description of the plant by the Greek physician Hippocrates
in the fifth century bce but one of the greatest challenges in St.
John’s wort research has been the failure to discover a single molecule to
account for the various medicinal efficacies. There have been 193 medicinal
metabolites reported in the literature on St. John’s wort (Hypericum
perforatum L.) and compiled in the NAPRALERT database (Murch et al.,
unpublished results). Hyperforin (Fig. 10.5) is thought to be involved in the
antidepressant activity of St. John’s wort through inhibition of reuptake of
several neurotransmitters and activation of nonselective cation channels
(Treiber et al. 2005). In vitro studies have shown that hyperforin interacts
with neurotransmitter transporter proteins and reduces the accumulation
H 3C
H 3C
O
H 3C
CH 3
N
O
N
CH 3
Caffeine
O
OH
N
N
CH 3
Δ-9-tetrahydrocannbinol
Hyperforin
N
O
CH 3
O
Nicotine
Fig.10.5. Commonly used neuroregulatory molecules from plants
N
O
OH