Chemical Warfare - Organic Pollutants: An Ecotoxicological Perspective - page 6

taBLe 1.1
Some toxins Produced by Plants

Pesticides acting
against Same target compounds mode of action comments

Pyrethrins Upon Na+ channel of

axonal membrane

Pyrethroids
p,p ′-DDT

Pyrethroids modeled on
pyrethrins

Veratridine Na + channel of axonal

membrane

Pyrethroids
p,p ′-DDT

Binding site appears to
differ from the one
occupied by pesticides

Physostigmine Anticholinesterase Insecticidal

carbamates

OP insecticides also act in
this way

Coumarol Vitamin K antagonist Warfarin

Superwarfarins

All act as anticoagulants
(Chapter 11)

Strychnine Acts on central nervous

system (CNS)

Used to control some
vertebrate pests

Rotenone Inhibits mitochondrial

electron transport

Used as an insecticide
(Derris powder)

Nicotine Acts on nicotinic receptor

for acetyl choline

Neonicotinoids An insecticide in its own

right and a model for
neonicotinoids

Precocenes Inhibit synthesis of juvenile

hormone in some insects

A model for the
development of novel
insecticides

Ryanodine Acts upon channels that

regulate Ca 2 + release

Phthalic acid
Diamides

Insecticides in the course of
development

Sources: Data from Harborne (1993), Eldefrawi and Eldefrawi (1990), Ballantyne and Marrs (1992),
Brooks, Pratt, and Jennings (1979), Salgado (1999), Copping and Duke (2007).

Copping and Duke 2007). Sabadilla was used by the native people of South and
Central America as an insecticide for many years.
Physostigmine (eserine) is a carbamate found in the calabar bean ( Physostigma
benenosum ), which acts as an anticholinesterase. It was used in West Africa in witch-
craft trials by ordeal. It has also been used in human medicine. Insecticidal carba-
mates are structurally related to it and also act as anticholinesterases (Ballantyne
and Marrs 1992).
Dicoumarol is found in sweet clover and can cause hemorrhaging in cattle because
of its anticoagulant action. It acts as a vitamin K antagonist and has served as a
model for the development of warfarin and related anticoagulant rodenticides.
Strychnine is a complex lipophilic alkaloid from the plant Strychnos nux-vomica ,
which acts as a neurotoxin. It has been used to control vertebrate pests, including
moles. The acute oral LD 50 to the rat is 2 mg/kg.