Ametryn metabolism

Figure 5. Proposed Pathways of Ametryn Metabolism in the Rat (Continued)...

Plant Ametryn is metabolized by tolerant plants into nontoxic hydroxy and dealkylated derivatives (Humburg et al., 1989). 

Alkylthiotriazines. In our laboratory we have studied the metabolic fate of 2-(4-ethylamino-6-methylthio- -triazin-2-ylamino)-2-methylpropionitrile (cyanatryn, 1, Fig. 1). This compound is a member of a class of herbicidal -triazines which also includes ametryne, prometryne and terbutryne. We were interested to note ( ) that two of the major metabolites of cyanatryn were the mercapturic acids 2-[A-ethylamino-6-(N-acetylcysteinyl)- -triazin-2-ylamino]-2-methylpropionitrTle (2.1) and its N-de-ethyl derivative (2.2) (Fig. 2). This pathway had not hitherto been reported for this class of compound. 

The triazine herbicides can be divided into four different structural classes chlorotriazines, methylthiotriazines, methoxytriazines, and atypical or asymmetrical triazines. The chlorotriazine group includes atrazine, simazine, pro-pazine, terbuthylazine, and cyanazine. The methylthiotriazine group includes ametryn, prometryn, and terbutryn. The methoxytriazine group will include prometon and secbumeton. Hexazinone and metribuzin were chosen to represent the atypical triazine group. The plant metabolism of the most researched member of each triazine group will be discussed in detail to cover all major biological and chemical transformations reported in the literature. 

Ametryn is used for preemergence and postemergence control of both monocotyledonous and dicotyledonous weeds in corn, sugarcane, banana, pineapple, and noncrop areas. The metabolism of ametryn in com (Detra and Chib, 1990a), sugarcane (Detra and Chib, 1990b), and banana (Thalaker and Ash, 1996) has recently been studied, and the major findings will be summarized by individual crop. 

Figure 7.8 The metabolic pathway of ametryn in banana (Thalaker and Ash, 1996).

Detra, R.L. and J.S. Chib (1990a). Metabolism of Triazine-I4C-Ametryn in Com. Submitted to USEPA. 

For the goat metabolism study, three lactating goats (one control and two treated) were dosed for a period of 3 days. The goats were orally administered approximately 75 mg/day ( 50 ppm dietary intake) of [i ]-ametryn for 3 consecutive days. 

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