A specific and sensitive assay to quantify the herbicidal activity of chloroacetamides

Abstract

: Based on a recently discovered property of chloroacetamide herbicidesÈthe inhibition of the incorporation of oleic acid into sporopollenin of Scenedesmus acutusÈa rapid quantitative test was developed for chloroacetamide-type herbicidal activity. In this test, algal cells are incubated for 3 h with [14C]oleic acid, saponiÐed and the lipids (including non-saponiÐable ones) extracted and discarded. The radioactivity incorporated into the residual non-lipid fraction is determined, and inhibition of this incorporation is used as a marker of chloroacetamide-type activity. Twenty-two agrochemical compounds were screened in this assay, which was found to be very sensitive, a 50% inhibition being reached with submicromolar herbicide concentrations. It is speciÐc to chloroacetamides and related amides, since all these herbicides tested were potent inhibitors, while other herbicides were not. Highest inhibition was shown by cafenstrole followed by butachlor, Ñuthiamid, metazachlor, alachlor, dimethenamid, metolachlor and mefenacet. For these herbicides (with the exception of butachlor) sensitivity in the test was positively correlated (r \ 0É984) with their phytotoxic e †ect on the alga.1998 SCI ( Pestic. Sci., 52, 381È387 (1998)

Finding the Target Site of Chioroacetamides: A Thorny Subject

“…It should be noted that growth inhibition of Scenedesmus correlates excellently with the inhibition of oleate incorporation. 30 Oxyacetamides like fluthiamid responded as expected. Apparently they share a primary target with chloroacetamides.…”

Very-Long-Chain Fatty Acid Biosynthesis is Inhibited by Cafenstrole, N,N-Diethyl-3-mesitylsulfonyl-1H-1,2,4-triazole-1-carboxamide and Its Analogs

“…(Couderchet et al, 1998) One-day old cultures of Scenedesmus acutus (no. 276-3a, Algae Collection, Göttingen, Germany) were concentrated to 50 [ig chlorophyll (Chi) ml-1.…”

“…Although the approximate I50 value for oleic acid elongation in Scenedesmus for com pounds 4, 5 and 6 were about 10_ 6m , the I50 value Table II Matthes et al (1998). * 2 for the assay with Scenedesmus cells see Couderchet et al (1998). The compounds were applied in water three days after transplanting of rice.…”

“…Its phytotoxic symptoms, namely impaired seedling emergence and stunting have been reported as very similar to those of chloroacetamide herbicides, such as alachlor or butachlor (Fukazawa et al, 1995). Re cently, a strong inhibition of very-long-chain fatty acid (VLCFA) biosynthesis by cafenstrole has been found in unicellular Scenedesmus cells (Couderchet et al, 1998), in cucumber cotyledons (Matthes et al, 1998), and with a cell-free micro somal preparation from leek seedlings (Allium porrum-, Böger et al, 2000). Incorporation of exog enously applied [14C]-oleic acid into an insoluble non-lipid fraction of Scenedesmus acutus cells was drastically decreased by the herbicide.…”

Synthesis and characterization of new soluble polyamides from Acenaphtohydrazinomercaptotriazole diamine

“…We have synthetized a diamin that produced of reaction of acenaphtochinon with Triazole derivatives and is used for production of thermally stable polyamides. Polyamides are characterized as high temperature resistant materials with a favorable balance of other physical and chemical properties [3] . Aromatic polyamides have the poor process ability due to their insolubility in common organic solvents and extremely high glass transition or melt temperature.…”