Evolution of Toxicity Upon Hydrolysis of Fenoxaprop-P-Ethyl

Jing Lin, Jingwen Chen, Xiyun Cai, Xianliang Qiao, Liping Huang, Degao Wang, Zhuang Wang

J Agric Food Chem. 2007 Sep 5;55(18):7626-9.

PMID: 17685541

Abstract:

Hydrolysis of fenoxaprop-p-ethyl (FE), a widely used herbicide, was studied in aqueous buffer solutions at pH ranging from 4.0 to 10.0. The degradation kinetics, strongly dependent on pH values, followed first-order kinetics. FE was relatively stable in neutral media, whereas it degraded rapidly with decreasing or increasing pH. In acidic conditions (pH = 4, 5), the benzoxazolyl-oxy-phenyl ether linkage of FE was cleaved to form ethyl 2-(4-hydroxyphenoxy)propanoate (EHPP) and 6-chloro-2,3-dihydrobenzoxazol-2-one (CDHB). While in basic conditions (pH = 8, 9, 10), herbicidal activity fenoxaprop-p (FA) was formed via breakdown of the ester bond of the herbicide. Both the two pathways were concurrent in neutral conditions (pH = 6, 7). Toxicity studies on Daphnia magna showed that FE was most toxic to D. magna with 48 h EC(50) of 14.3 micromol/L, followed by FA (43.8 micromol/L), CDHB (49.8 micromol/L), and EHPP (333.1 micromol/L). Mode of toxic action analysis indicated that EHPP exhibited toxicity via polar narcosis, whereas CDHB belonged to reactive acing compound. The mixture toxicity of CDHB and EHPP was nonadditive and can be predicted by a response addition model. Therefore, the evaluation of overall FE toxicity to D. magna in the aquatic systems needs to consider the degradation of FE.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP71283802	Fenoxaprop-P-ethyl		71283-80-2	Price

Catalog Number

Product Name

Structure

CAS Number

Price

AP71283802

Fenoxaprop-P-ethyl

71283-80-2

Price

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