The Metabolism of Atrazine and Related 2-Chloro-4,6-bis(alkylamino)-s-triazines in Plants

Abstract

The metabolism of atrazine and related 2-chloro-4,6-bis(alkylamino)-s -triazine herbicides in plants is reviewed and the structures of 13 metabolites recently identified from mature plants grown in the field are reported. The 2-chloro-4,6-bis(alkylamino)-s-triazines are initially metabolized in plants by three competing reactions: hydrolytic dehalogenation, N-dealkylation, and glutathione (GSH) conjugation. Metabolites produced by N-dealkylation can be further metabolized by hydrolytic dehalogenation or GSH conjugation, those produced by hydrolytic dehalogenation can be further metabolized by N-dealkylation and it is proposed that those from the GSH conjugation pathway may slowly become hydroxylated at the 2-position of the triazine ring. Ten metabolites of atrazine have been identified from the N-dealkylation and hydroxylation pathways and 14 have been identified from the GSH conjugation pathway. Three additional metabolites that have an amino function on the 2-position of the triazine ring have been identified, but their route of formation is uncertain.2-Chloro-4,6-bis(alkylamino)-i-triazine (2-chloro-.s-triazine) metabolism in plants has been extensively studied and comprehensive reviews have been written on the chemical and physical properties, metabolism and mode of action of these compounds (7) and on their metabolism and selectivity in plants (2). Based upon numerous studies conducted since the first patent was filed for these herbicides in 1954, the 2-chloro-5"-triazines such as atrazine (2-chloro-4-ethylamino-6-isopropylamino-5-triazine), simazine (2-chloro-4,6-bis[ethylamino]-s-triazine), and propazine (2-chloro-4,6-bis[isopropylamino]-^-triazine) have been shown to be metabolized in plants by three competing initial reactions: N-dealkylation of the side-4 Current Address: ABC Laboratori es Cal i forni a, Madera, CA 93638 60

Function of phytochelatin synthase in catabolism of glutathione‐conjugates

“…, 1998; Marrs et al. , 1995) as well as a diverse range of xenobiotics, including widely used herbicides, the chloro‐ S ‐triazine herbicides such as atrazine, and the sulphonylurea herbicide chlorimuron ethyl (Lamoureux and Rusness, 1993; Lamoureux et al. , 1991, 1998).…”

Characterization of the Hypothalamic-Pituitary-Adrenal Axis Response to Atrazine and Metabolites in the Female Rat

“…The biotransformation of this compound in the environment and metabolism in plants primarily produces hydroxyatrazine and the chlorinated metabolites desisopropylatrazine (DIA), desethylatrazine (DEA), and diamino-s-chlorotriazine (DACT, Fig. 1) (Koskinen and Clay, 1997;Lamoureux et al, 1998). Studies of ATR metabolism within humans and animals indicate the presence of the chlorinated metabolites as well as mercapturated forms (Bakke et al, 1971;Barr et al, 2007;Catenacci et al, 1990;Ikonen et al, 1988).…”

Transgenic Rice Plants Expressing Human P450 Genes Involved in Xenobiotic Metabolism for Phytoremediation

“…In higher plants, atrazine is metabolized by hydroxylation, dealkylation, and glutathione conjugation. N-dealkylation of atrazine occurs in many plant species, with preferential formation of deethylated atrazine over deisopropylated atrazine [Lamoureux et al, 1998]. N-dealkylation of a single side-chain results in a partial loss of phytotoxicity, and N-dealkylation of both side-chains causes complete loss of phytotoxicity [Shimabukuro et al, 1973].…”