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Man as a biological species and as a member of the community of
organisms that has evolved over the billions ofyears on this planet
has to face competition for his resources in the same way as any
other species. In the course of evolution organisms have developed
a fascinating variety of weapons, techniques and strategies in this
competitive scramble for food and other essential resources and in
se1f-defense against parasitism and predation. Among these, the
biosynthesis of toxic molecules and their appropriate delivery in
interspecific encounters has proved to be one of the most
successful natural weapons and has been demonstrated in every
branch of the evolutionary tree of all extant species. It is
interesting to note that in this process of generating toxic
molecules both natural se1ection by evolutionary processes and
screening techniques by chemical industry have produced compounds
with very similar target sites. The most potent of these compounds
interfere with the normal signalling of nerve cells. Saxitoxin,
tetrodotoxin, batracho- toxin, grayanotoxin, veratridine, aconitin,
sea anemone venom and scorpion toxin are natural poisons which
interfere with the same membrane bound protein as many potent
synthetic insecticides such as DDT and the pyrethroids: the
voltage-gated Na + channe1 in the nerve cell membrane. In several
cases natural toxins have direct1y provided lead structures for
successful chemical synthesis programmes in the insec- ticide
industry. Eserine, nereistoxin and pyrethrum are outstanding
examples.
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