Table 1
Pyrethroid enantiomers and their isomer ratios on commercial formulations
Pyrethroids
Type
Chiral
carbons
cis-Isomers
a
trans-Isomers
a
Isomer ratio
(cis/trans)
Total
isomers
References
Permethrin
I
2
1R-cis;
1S-cis
1R-trans;
1S-trans
80:20; 40:60;
25:75
b
4
[ 24–26]
cis-Bifenthrin
I
2
1R-cis;
1S-cis
–
cis
!97%
2
[8, 17]
Resmethrin
I
2
1R-cis;
1S-cis
1R-trans;
1S-trans
20–30:70–80
c
4
[ 3, 24]
Bioresmethrin
I
2
–
1R-trans
Isomer
!90%
1
[8, 24]
Phenothrin
I
2
1R-cis;
1S-cis
1R-trans;
1S-trans
50:50
4
[8]
Cypermethrin
II
3
1R-cis-αR; 1S-cis-αS; 1R-cisαS; 1S-cis-αR
1R-trans-αR; 1S-trans-αS; 1S-transαR; 1R-trans-αS
45:55
8
[24, 27]
alphaCypermethrin
II
3
1R-cis-αS;
1S-cis-αR
–
–
2
[ 8]
beta-Cypermethrin
II
3
1R-cis-αS;
1S-cis-αR
1S-trans-αR; 1R-trans-αS
40:60
4
[8]
theta-Cypermethrin
II
3
–
1S-trans-αR; 1R-trans-αS
50:50
2
[8]
zeta-Cypermethrin
II
3
1S-cis-αS; 1R-cis-αS
1S-trans-αS; 1R-trans-αS
45–55:55–45
c
4
[ 8, 27]
Deltamethrin
II
3
1R-cis-αS
–
Isomer
!98%
1
[8]
Fenvalerate
II
2
2S-αS;
2R-αR
2R-αS; 2S-αR
50:50
4
[28]
Esfenvalerate
II
2
2S-αS
–
Isomer
!75%
1
[8, 28]
lambdaCyhalothrin
II
3
1R-cis-αS;
1S-cis-αR
–
–
2
[ 8, 17]
gamma-Cyhalothrin
II
3
1R-cis-αS
–
Isomer
!98%
1
[29]
Cyfluthrin
II
3
1R-cis-αR;
1S-cis-αS; 1R-cisαS; 1S-cis-αR
1R-trans-αR; 1S-trans-αS; 1S-transαR; 1R-trans-αS
45–55:55–45
c
8
[ 27, 30]
beta-Cyfluthrin
II
3
1R-cis-αS; 1S-cis-αR
1S-trans-αR; 1R-trans-αS
33:66
4
[8]
Bold enantiomers have higher insecticidal activity than the other enantiomers
a
cisand trans-isomerism
from pyrethroids are related to their Ror S-configurations
of chiral carbons (C-1 and C-3) on the cyclopropane ring
b
Different permethrin isomeric ratios are related to the manufacturing processes; however, technical formulation with predominance of trans-isomers,
e.g. 40:60
and 25:75, is more common [25]
c
Expected variation during the manufacturing process
156
C. E. T. Parente et al.