title: Toxicity of binary mixtures of enantiomers in chiral organophosphorus insecticides: the significance of joint effects between enantiomers.
abstract: The existence of enantiomer-enriched mixtures of chiral pesticides in the environment is overwhelmingly positive. However, interactions between enantiomers have not been considered so far in risk assessments. Here, we chose three organophosphorus pesticides as representative chiral pesticides to investigate the possible interaction mode between each pair of enantiomers both in in vivo and in vitro. Data show that the enantiomers of methamidophos and profenofos have a simple additive effect, <zaq;1> whereas fensulfothion acts as an antagonist in AChE-inhibition model. In contrast, enantiomers of methamidophos and fensulfothion had an additive effect in an acute toxicity test against Daphnia magna. A synergistic effect was observed in the joint toxicity of the profenofos enantiomers. The ability for enantiospecific biodegradation in the in vivo model contributed to the different interaction observed between the in vitro and in vivo models. Moreover, binding affinities were suspected as another reason for the different mode of action of mixture enantiomers. Our study recommends using a joint research model to treat chiral compounds in the real environment.
authors.affiliation: College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Zhang
authors.forename: Cui
authors.initials: C
authors.lastname: Wang
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D002800:Cholinesterase Inhibitors / Q000737:chemistry* / Q000633:toxicity*; D003621:Daphnia / Q000187:drug effects; D007306:Insecticides / Q000737:chemistry* / Q000633:toxicity*; D009943:Organophosphorus Compounds / Q000737:chemistry* / Q000633:toxicity*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D002800:Cholinesterase Inhibitors; D007306:Insecticides; D009943:Organophosphorus Compounds; D000110:Acetylcholinesterase
keywords: chiral pesticides; enantiomers; factorial design; joint toxicity; risk assessment