Assessing the Efficacy-Risk of the Widely Used Chiral Glufosinate: Switch from the Racemate to the Single Enantiomer?

Abstract

The chirality of pesticides has emerged as an important issue in pesticide design and applications because enantiomers can differ greatly in their environmental fate and risk. Despite the increasing concern over the unintended effects of inactive or less effective enantiomers, massive amounts of chiral pesticides are applied as racemic mixtures. As a potential substitute for glyphosate, the market of glufosinate is expected to grow rapidly. However, very little information is available on its enantioselective efficacy-risk assessment, especially at the environmentally relevant concentration. The overall aim of this study is to determine if the switch from glufosinate racemic mixture to l-glufosinate was favored regarding environmental health. Thus, we examined (i) the herbicidal activity of Rac- and l-glufosinate to the weed, Echinochloa crus-galli, and (ii) adverse effects on nontarget zebrafish (Danio rerio). Significant higher herbicidal activities were achieved by l-glufosinate at both 1 and 5 mg/L. Embryotoxicity and teratogenicity are significantly different: Rac-glufosinate induced a significantly higher lethality (LC50 = 17.29 mg/L) and malformations. The oxidative stress markers, including superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA), were preferably induced by Rac-glufosinate at mRNA and enzymatic activity levels. In summary, we suggest that l-glufosinate should be applied preferably over Rac-glufosinate.

Glufosinate‐ammonium: a review of the current state of knowledge

“…A recent study has shown that L-phosphinothricin was favored in an efficacy-risk assessment by better inhibiting weed growth and less early life toxicity to offtarget organisms compared to the racemic mixture. 45 Since glufosinate and its metabolites are highly water soluble, they neither volatilize nor accumulate in the food chain (Table 1). 1 Glufosinate does not remain in the soil because it is rapidly degraded by soil bacteria, resulting in no residual activity nor crop rotation restrictions.…”

“…Alternatively, switching from the racemate to the single enantiomer could reduce by half the total amount of glufosinate applied to the environment. A recent study has shown that L‐phosphinothricin was favored in an efficacy‐risk assessment by better inhibiting weed growth and less early life toxicity to off‐target organisms compared to the racemic mixture 45 . Since glufosinate and its metabolites are highly water soluble, they neither volatilize nor accumulate in the food chain (Table 1).…”

The potential future roles of natural compounds and microbial bioherbicides in weed management in crops

“…The commercial product is a racemic mixture of the active, pure L-glufosinate which is identical to phosphinothricin and the inactive D-glufosinate (Copping, Duke, 2007). Efforts are being made to economically produce the L-enantiomer, the use of which would be advantageous to reduce crop injury and for potential toxicological reasons (Takano, Dayan, 2020;Yue et al, 2020). There are numerous other natural GS inhibitors that are not commercialized as herbicides (Lydon, Duke, 1999), perhaps because of high cost and/or inadequate physicochemical properties.…”

A new chiral stationary phase based on noscapine: Synthesis, enantioseparation, and docking study

“…2.3 | Synthesis of the noscapine derivative chiral stationary phase 2.3.1 | Synthesis of N-nornoscapine; (3S)-6,7-dimethoxy-3-[(5R)-4-methoxy-5,6,7,8-tetrahydro- [1,3]dioxolo[4,5-g]isoquinlin-5-yl]-2-benzofuran-1(3H)-one (2)…”

“…Enantioseparation is of great importance in both pharmaceutical and biological industries 1 because in most cases, single enantiomers are mainly more active, selective, preferable, and less toxic as compared to racemates. 2,3 However, it is noteworthy that the development of a chiral pharmaceutical ingredient in a racemic form can be more affordable for the pharmaceutical industry. 4 Resolution of enantiomers is achievable using different techniques such as crystallization, [5][6][7] capillary electrophoresis (CE), [8][9][10] and chromatography.…”