Relationships between Insecticidal Activity of 6-Alkylthio-2-pyridyl Methanesulfonates and Acetylcholinesterase Inhibition of their Sulfone Derivatives against <i>Nephotettix cincticeps</i>

Abstract

The inhibitory activity (I50) of fifteen sulfone analogs of 6-alkylthio-2-pyridyl methanesulfonates was measured against acetylcholinesterase preparations from Ageo and Izumi strains of Nephotettix cincticeps. The insecticidal activity of 6-alkylthio derivatives to both strains was highly related to the acetylcholinesterase-inhibitory activity of the corresponding sulfones when hydrophobicity factors (log h) of the molecule perhaps participating in the transport process were taken into account.Variations in insecticidal activity was due to the total of structure-activity relationships in enzyme inhibition and transport process. The combination of hydrophobicity and steric parameter terms was quite similar in the two strains.

Cholinergic Activity of Selected Methanesulfonate Insecticides. A Pharmacological Profile

“…Our tests on B. germanica (German cockroach) confirmed the insecticidal activity of the parent compound 6 This activity most probably results from inhibition of cholinesterase, as indicated in biochemical assays of fly head acetylcholinesterase. However, the sulfone (111) was found to be inactive when applied to the blowfly, L. cuprina, which may be due to its lower lipid solubility and consequent lack of penetration through the insect cuticle.…”

Insecticidal and Antiacetyicholinesterase Activities of Isobutylthioaryl Methanesulfonates

“…To P. xylostella, only the 2-isobutylthio-4pyridyl (5) and -5-thiadiazolyl (13) derivatives were active. With seven compounds (1)(2)(3)(4)(5)(6)9) the mortality of C. pipiens reached 100%. Only 6-isobutylthio-2-pyridyl methanesulfonate (2) was active to T. urticae.…”

“…Optimum hydrophobicity2) and stability against hydrolysis are two important factors for compound to be highly active. Among the aryl methanesulfonates shown in Table 2, the hydrophobicity of 3-isobutylthio-phenyl derivative (1) was far apart from the optimum, which has been shown to be 0.19 to the Ageo and 0.22 to the Izumi strain of N. cincticeps in terms of log k'.4) This may be one reason for the lower activity of phenyl derivative (1) compared with pyridyl derivatives (2)(3)(4). Two pyrimidine analogs (7,8) which were less active than the pyridine analogs (2-4) were labile against hydrolysis, while the pyrazinyl (6) and thiazolyl (9) analogs were moderately stable.…”