Insect Control: Biological and Synthetic Agents - Index of

Figure 2 Structures of pyrazoline-like Na þ channel blockers.
physical, toxicological, and environmental properties
are shown in Table 1; the profile indicates a safe,
environmentally benign compound with relatively
low water solubility.
2.3. Metabolism and Bioavailability
of Indoxacarb
2.3.1. Bioactivation of Indoxacarb
Indoxacarb requires metabolic activation by insects
before it acts as a strong Na þ channel blocker
(Figure 4). An esterase or amidase-type of enzyme(s)
cleaves the carbomethoxy group from the urea
linkage, liberating the free urea DCMP, which then
2: Indoxacarb and the Sodium Channel Blocker Insecticides 37
Figure 3 Structure–activity relationships for oxadiazine insecticides vs. Spodoptera frugiperda.
acts as the voltage-dependent Na þ channel blocker.
This was first demonstrated for the racemic compound
DPX-JW062 (50 : 50 mixture of active S and
inactive R enantiomers) being converted to the corresponding
N-decarbomethoxylated DPX-JW062
(DCJW) (Wing et al., 1998). The enzyme involved
has been only partially characterized. It is clear
that the enzyme is a hydrolase of some type, may
be serine dependent. In Lepidoptera the enzyme
is found in high concentrations in midgut cells (but
not the gut contents) and in fat body, and also
found in high concentrations in several subcellular
fractions (nuclear, mitochondrial, microsomal, and
cytosolic). The enzyme can be inhibited by several