Alteration of Diphenamid Metabolism in Tomato by Ozone

Abstract

Fumigation of tomato (Lycopersicon esculentumMill. ‘Sheyenne’) with low levels of O3had little effect on root absorption, translocation, or conversion of diphenamid (N,N-dimethyl-2,2-diphenylacetamide) to water-soluble conjugates. However, the proportion of specific conjugates was markedly altered in O3-fumigated plants. Twenty-four hours after treatment, the predominant conjugates formed in nonfumigated and fumigated tomato were the β-glucoside (MDAG), and the β-gentiobioside (MDAGB), respectively, ofN-hydroxymethyl-N-methyl-2,2-diphenylacetamide. The ratio MDAG:MDAGB was 8.2:1.0 in nonfumigated tissue and 0.6:1.0 in O3-fumigated tissue. This marked shift toward production of the more polar MDAGB was accompanied by a trend toward increased production of methanol-insoluble residues. A compound having limited stability was extracted from tomato; its probable structure wasN-hydroxymethyl-N-methyl-2,2-diphenylacetamide (MODA). It is a postulated intermediate in the formation of MDAG and MDAGB from diphenamid.

Translocation and Metabolism of the Acaricide Fenothiocarb in Citrus

“…The enzyme specificity to the conjugate of a pesticide has been reported in the study of /3-glucoside of N-hydroxymethylated diphenamid herbicide. 21 To identify the acidic glycoside moiety, the conjugate purified by TLC was hydrolyzed in 1 N HCl (in 50 ,al, 12 hr at room temp.). The hydrolysate was spotted directly on the TLC plate, and developed with solvent system C or D. Glucose and malonic acid are tentatively identified by comparison with the standards.…”

Pesticide Conjugates-Glycosides

“…Studies with the herbicide, diphenamid (N,N-dimethyl-2,2-diphenylacetamide), have shown that a primary oxidation product, N-hydroxymethyl-N-methyl-2,2-diphenylacetamlde, is conjugated as a 3-glucoside and a 3-gentiobioside (59). Structures were determined by MS of acetylated derivatives and analysis of hydrolysis products.…”

“…It is also interesting to note that the activities of these enzymes are affected by environmental factors such as ozone levels (59,60) or light intensity and humidity (63).…”

“…The isolation and identification of the glucoside and gentiobioside of N-hydroxymethyl-N-methyl-2,2-diphenylacetamide presented some interesting and challenging problems (59). The most difficult problem was the separation of the highly polar gentiobioside from naturally occurring glycolipids.…”

“…The mild conditions needed for the recovery of the unchanged glycoside are also helpful in situations where the glycoside is easily hydrolyzed. Another interesting lesson learned in diphenamid metabolism studies (59) was that failure to demonstrate metabolite hydrolysis with emulsin does not preclude the presence of a 3-D-glucoside. The glucoside metabolite of N-hydroxymethyl-Nmethyl-2, 2-diphenylacetamide was not hydrolyzed by emulsin, and the gentiobioside was hydrolyzed partially at the 3-1,6 linkage to yield the glucoside.…”