Chemistry Reference
In-Depth Information
Carbamates include aldicarb, methiocarb, methomyl, carbofuran, ben-
diocarb and oxamyl. Although they are broad-spectrum insecticides, with
moderate toxicity and persistence, they rarely bioaccumulate or cause major
environmental impacts [25].
O
N
O
Carbamate linkage
O
CH
3
O
H
N
CH
3
H
3
C
S
CH
3
N
O
H
3
C
S
CH
3
N
CH
3
O
N
CH
3
O
S
CH
3
Methiocarb
O
Aldicarb
Methomyl
O
O
CH
3
CH
3
N
N
H
O
N
H
O
N
O
O
O
O
N
CH
3
S
CH
3
O
O
Carbofuran
Bendiocarb
Oxamyl
Pyrethroid insecticides are widely used because of their high activity as an
insecticide and low mammalian toxicity. Pyrethroids are in group 3, sodium
channel modulators. The pyrethroids have a highly nonpolar nature, low water
solubility, and high affinity to soil and sediment particulate matter. Natural
pyrethrin is extracted from the flowers of
Chrysanthemum
spp., and its use
was already known in China in the first century A.D. Pyrethroids, synthetic
analogues of pyrethrin, have been produced since 1940 [26].
The six pyrethrins, Pyrethrin I, Jasmolin I, Cinerin I, Pyrethrin II, Jas-
molin II, and Cinerin II were found to be present in the leaf extract of the
Chrysanthemum cinerariaefolium
seedlings. Pyrethrins are thought to act as
defense mechanisms that prevent insects from feeding on the plant [27]. The
pyrethrins repel insects and also paralyze flying insects, thereby exhibiting a
“knock-down” effect. The active components occur to a small extent in all
parts of the plant, but especially in the flower heads [28].
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