Pesticide Metabolism in Plants
glu-cys-gly
I
_" ¢' ,O,
/ ", +6
FLUORODIFEN
o
II H
CH 3 -C-N- y H-COOH
yH2
¢c
CF 3 \
H2N- y HCOOH
yH2
¢' ,O,
CF 3
EXCRETED
IN URINE
o
0
II
II
N02
jPEANUT
GLUCSIDE +
MALONYL GLUCOSIDE
HO-C-CH2-C-N-9H-COOH
9 H2
¢',~
/
CF 3
INSOLUBLE
RESIDUE?
Figure 2.25. Metabolism of ftuorodifen by glutathione conjugation in peanuts and rats.
53
detoxication of chlorfenprop-methyl in resistant wheat coleoptiles was postulated
to be a direct displacement of the alkyl chlorine by cysteine (Collet and Pont,
1978) following partial detoxication by deesterification. The cysteine conjugation
showed very little physiological activity as compared to the parent methyl ester
and free acid (Collet and Pont, 1978). No mercapturic acids were identified as
metabolites of the two cysteine conjugates.
The limited number of examples indicates that because an appropriate substrate is metabolized by an initial reaction with glutathione in one system, e.g.,
an animal system, it is no assurance that it will be metabolized in a corresponding
manner in another system, e.g., a plant system. The chloro-s-triazines are metabolized to a large extent in plants by glutathione conjugation, and animals
appear to have the necessary enzymes to metabolize these compounds similarly.
However, glutathione conjugation is not a general method of metabolism of 2-