Toxins in Nature - Natural Products Chemistry: Sources, Separations, and Structures - page 155

14 Toxins in Nature
One of the biggest “poison” myths is the suggestion that “all-natural” or “organic”
substances are safe and safer than the man-made or derived “chemical” counterparts.
The fact is some of the most toxic substances known are from nature. This chap-
ter provides examples of toxins drawn from various sources: plants, mushrooms,
spiders, marine algae, fish, snails, and frogs. The examples not only represent the
diversity of the chemical sources found in nature but how their different chemical
structures contribute to severe toxic effects and in most cases can lead to death.
14.1 EXAMPLES OF TOXINS FROM PLANTS
Aristolochic acids—Aristolochic acids (Figure 14.1) are commonly used in
Chinese herbal medicine even though they are a family of carcinogenic
mutagenic and nephrotoxic compounds found in Aristolochia and Asarum
(wild ginger). Extreme care of preparation and use is required.
Monkshood ( Aconitum napellus )—The toxin in this plant is known as aconi-
tine (Figure 14.2 and Figure 14.4b). Aconitine and related alkaloids found
in the Aconitum species are highly toxic cardiotoxins and neurotoxins.
Symptoms include tingling, numbness and paralysis, violent gastrointes-
tinal symptoms, and intense pain. Death is usually due to cardiac arrhyth-
mias. However, there are traditional uses of this plant. For example, the
roots of Aconitum ferox yield the Nepalese poison called nabee . It contains
large quantities of the alkaloid pseudaconitine, which is a deadly poison and
used by various Asian communities as arrow poisons to hunt ibex and bear.
In Traditional Chinese Medicine, aconite roots are used only after process-
ing to reduce the toxic alkaloid content. However, the use of a larger than
recommended dose and inadequate processing increases the risk of poison-
ing. The wild plant (especially the roots) is extremely toxic. Reduction of
the toxic alkaloid content is achieved by soaking and boiling to hydrolyze
aconite alkaloids into less toxic and nontoxic derivatives.
Water hemlock ( Cicuta species)—The toxic principle cicutoxin (Figure 14.3 and
Figure 14.4a) is known for causing seizures. Fatal cases have been reported
as a result of people eating a water hemlock plant they thought was a wild
parsnip or other root vegetable. One mouthful can be fatal and in the United
States water hemlock is considered one of North America's most toxic plants
to humans.
Castor bean ( Ricinus communis )—Castor beans contain toxic albumins, which
are cellular toxins. As little as one seed fully chewed and swallowed can
be fatal in a child. The toxins are identified as the Ricin A chain and Ricin
B chain and are of similar molecular weight. Thus, the Ricin A chain is
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