Metabolic Fate of Phenothrin in Plants and Soils

Abstract

+)-Traps and (+)-cis isomers of phenothrin [3-phenoxybenzyl (+)-cis, traps-chrysanthemate] labeled with 14C at the methylene group of the alcohol moiety disappeared rapidly from the treated leaves of bean and rice plants with half-lives of less than one day under greenhouse conditions. On and/or in these plants, both isomers underwent ozonolysis at the isobutenyl double bond to yield ozonides of phenothrin isomers which were rapidly decomposed to the corresponding aldehydes and carboxylic acids. These ester products were further metabolized via cleavage of the ester linkage, hydroxylation at 2'-and 4'-positions of the alcohol moiety, and oxidation of benzyl alcohols to benzoic acids. The resulted alcohols and carboxylic acids were subsequently conjugated with sugars. Bean plant seedlings planted in Kodaira soil, Katano soil and Muko sand treated with 1. 0 ppm of 14C-phenothrin isomers took up very little 14C into shoots, and pods and seeds, whereas roots retained 0. 21-3. 48 ppm of 14C. No parent compounds were detected in shoots. 14C-Phenothrin isomers were rapidly decomposed in Kodaira and Katano soils with half-lives of 1 to 2 days under upland conditions. On the other hand, degradation of both isomers was much slower under flooded conditions, and half-lives were 2 to 4 weeks and 1 to 2 months for the (+ )-traps and (+)-cis isomers, . respectively.Degradation of phenothrin isomers in the soils proceeded via cleavage of the ester linkage, hydroxylation at 4'-position of the alcohol moiety, cleavage of the Biphenyl ether linkage and oxidation of benzyl alcohols to benzoic acids. These products were not persistent in the soils under both conditions and the labeled carbon was finally decomposed to 14CO2.

Photodegradation of insecticide metofluthrin on soil, clay minerals and glass surfaces

“…The typical concentration of atmospheric O 3 is known to be 20-70 ppb 4) and its participation in the degradation of pesticides has been reported on soil and glass surfaces, 20,21) and plant foliage. 13,21) Ozonolysis of alkenyl bond is a typical reaction and has been previously reported for some pyrethroids. 13,22) Under light conditions at Ͼ290 nm, O 3 is scarcely photo-produced from molecular oxygen (O 2 ) because higher energy at Յ240 nm is required for the reaction; 23) therefore, ozonide IX (1,2,4-trioxolane) was most likely to be formed from the primary ozonide (1,2,3-trioxolane) via reaction with atmospheric O 3 introduced into the reaction chamber.…”

“…The non-radiolabeled isomers of I, the corresponding chrysanthemic acid derivatives (VII and VIII) and alcohols (V and VI) together with the oxidized esters (II, III and IV) were synthesized in our laboratory according to the reported methods. 1,11,12) The ozonide derivative IX, consisting of four isomers, was prepared by ozonolysis 13) of I-RTZ. Ozone gas generated via electrical discharge was introduced by gentle bubbling to nhexane solution (5 mL) of I-RTZ (35 mg) for 3 min at Ϫ78ºC.…”

Aerobic metabolism and adsorption of pyrethroid insecticide imiprothrin in soil

“…28) The major degradation product from the acid moiety of IP by ester cleavage is most likely to be 2,2-dimethyl-3-(2-methylprop-1-enyl) cyclopropanecarboxylic acid which undergoes rapid degradation to carbon dioxide and/or is bound to soils, as reported for other pyrethroids such as phenothrin. 2) Based upon the decline and formation profiles of the identified degradates (Table 3), degradation pathways of IP under aerobic conditions are proposed in Fig. 4.…”

“…1) The metabolic profiles of synthetic pyrethroids such as phenothrin, 2) permethrin, 3) cypermethrin 4,5) and fenvalerate, 6,7) have been extensively investigated in aerobic soils and their variable degradability with half-lives of 1 day-16 weeks was found to significantly depend on either soil characteristics or microbial activity. 8,9) Their main degradation pathways are the hydrolytic cleavage of an ester linkage, stepwise hydration of a cyano group, cleavage of a diphenyl ether bond and ring hydroxylation of a phenoxybenzyl moiety.…”

Hydrolysis and photolysis of insecticide metofluthrin in water

“…7) The main photoproduct IV can be synthesized by exposure to ozone in the presence of triphenylphosphine, which indicates a reaction through ozonide, whose existence was reported for the plant metabolism study of phenothrin. 20) This indicates that both direct and indirect photolytic reactions play an important role in the dissipation of I under environmental aquatic conditions.…”