Organophosphorus and Carbamate Insecticides - Organic Pollutants: An Ecotoxicological Perspective - page 198

S CH 3

CH 3

C 2 H 5 O
C 2 H 5 O

N CH 3

P O

N

Glutathione-
dependent
desethylase

Diazinon

CH 3

MO

-OH

O

CH 3
CH 3

CH 3
CH 3

C 2 H 5 O
C 2 H 5 O

N N

CH CH

Mainly
'A' esterase

P O HO

N N

MO

CH 3 CH 3

Uncharacterised
metabolites

Diazoxon

S

C 2 H 5 O
C 2 H 5 O

P S CH 2 CH 2 S C 2 H 5 Disyston

MO

MO

S O O

C 2 H 5 O
C 2 H 5 O

C 2 H 5 O
C 2 H 5 O

P S CH 2 CH 2 S C 2 H 5 P S CH 2 CH 2 S C 2 H 5

Oxon form

MO MO MO

S O O O

C 2 H 5 O
C 2 H 5 O

C 2 H 5 O
C 2 H 5 O

P S CH 2 CH 2 S C 2 H 5 P S CH 2 CH 2 S C 2 H 5

Sulphoxide

O

MO

S O O

C 2 H 5 O
C 2 H 5 O

C 2 H 5 O
C 2 H 5 O

P OH P SCH 2 CH 2 SC 2 H 5 S

O

+

O

HS CH 2 CH 2 S C 2 H 5

Sulphone

O

Principally
'A' esterase

O

C 2 H 5 O
C 2 H 5 O

P OH

HSCH 2 CH 2

O

+

SC 2 H 5

O

S S S

CH 3 O
CH 3 O

CH 3 O
CH 3 O

CH 3 O
CH 3 O

SH + P P OH P S CHCOOC 2 H 5 Malathion

monoacid

CH 2 COOH

Carboxyesterase
( 'B' esterase )

S

CH 3 O

*

P S CHCOOC 2 H 5

CH 2 COOC 2 H 5

Malathion

CH 3 O

*

MO

O

CH 3 O

*

P S CHCOOC 2 H 5

CH 2 COOC 2 H 5

Malaoxon

CH 3 O

*

Principally
'A' esterase

* Removable by MO attack

O

CH 3 O
CH 3 O

P OH

fIgure 10.2 Metabolism of OPs.