Chemistry Reference
In-Depth Information
HISTORICAL NOTE
In the 1970s, scientist John Daly began a collection of poisonous frogs from
the Ecuadorian Highland, and through this work discovered an alkaloid
possessing interesting biological properties. However, due to ecological con-
siderations, the research was banned by the protection of endangered species.
Furthermore, scientists were unable to raise these frogs with secretion-
containing alkaloids in their laboratories.
analgesic compound and hope was given this would be a lead compound for analge-
sic drug development.
Chemically, epibatidine is a hygroscopic oily substance that can act as a base.
The ive-membered ring is part of the 7-azabicyclo [2.2.1] heptane structure with
exo-oriented chloro and pyridyl substituents.
From X-ray diffraction studies epibatidine is levorotatory and the configuration is
established as 1R, 2R, and 4S. The frog skin extracts were further purified on a pre-
packed silica gel 60 column (chloroform-methanol-aqueous ammonia and after con-
centration purified by HPLC using aqueous (NH 4 ) 2 CO 3 as a solvent). Biologically,
these actives behave as neurotoxins, with high affinity to the acetylcholine recep-
tors: nicotinic and muscarinic acetylcholine receptors. Thus, they have the effect of
causing analgesia at low doses, however, reports of paralysis, loss of consciousness,
coma, and even death were seen at high doses.
SUMMARY
This final chapter highlights nature's toxic compounds. Examples are shown
of spider, conus snail, and frog venoms. Examples of marine toxins from algae
include the saxitoxins and brevitoxins. Marine toxins from fish include ciguatoxin
and tetrodotoxin.
QUESTIONS
1. How might you isolate red tide toxins from marine sources?
2. What spectroscopic techniques would be useful to help and finally deter-
mine the structure of a brevitoxin compound?
3. How might you isolate the saxitoxin compounds?
4. Some saxitoxins contain an SO3 group. How might this group be identified?
5. How might its position in the molecule be determined?
6. Epibatidine is an alkaloid found in certain frogs. How might you undertake
the isolation of such a compound?
 
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