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O -
OH
+
NH 2
O
O
OH
H
HO
NH
HO
OH
FIGURE 14.10 The chemical structure of the toxin obtained from the blowfish “fugu”
named tetrodotoxin.
14.5 SPIDER VENOM
Agelenopsis aperta , commonly known as the desert grass spider, is a species of spi-
der belonging to the family Agelenidae. It is found in dry regions across the southern
United States and into Mexico. The venom of the spider is composed of a family of
proteins that function as neurotoxins. The biological mechanism of action of the spi-
der toxin is the blockage of calcium channels or acting as potassium channel inhibi-
tory toxins. An example is the compound hanatoxin, a 35-amino acid peptide toxin
isolated from the Chilean rose tarantula venom, which inhibits the voltage-gated
K-channel by altering the energetics of gating.
14.6 CONUS SNAIL TOXINS
Conus snails are large mollusks and they use a toxic venom to immobilize their prey.
The toxin is a mixture of conopeptides and usually consists of between 10 and 30
amino acids. Their mode of action targets different voltage- and ligand-gated ion
channels. Several conopeptides have been taken into the clinic and one peptide has
received approval for the treatment of pain. The peptides are produced synthetically
using solid phase peptide synthesis.
14.7 POISONOUS FROGS
Poisonous substances can be found on the skin of a kind of poison dart frog named
Epipedobates tricolor . These frogs inhabit the rainforests of Ecuador and the poison
is used by Amerindian tribes to make poison arrows. The compound epibatidine
(Figure  14.11), a new class of alkaloid, was discovered in 1992, exhibiting a rare
example of an alkaloid with a Cl substituent. Biological tests showed it is a nonopioid
H
N
CI
N
FIGURE 14.11 The chemical structure of the toxin epibatidine (1R,2R,4S)-(+)-6-(6-chloro-
3-pyridyl)-7 azabicyclo-[2.2.1]heptane.
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