Trifloxystrobin: a very broad spectrum foliar fungicide

Introduction

Methyl (E)-methoxyimino-{(E)-α-[l-(α, α, α-trifluoro-m-tolyl)ethylidene-aminooxy]-o-tolyl} acetate (also known as Trifloxystrobin ), CAS Reg. No. 141517-21-7 was discovered by Novartis Crop Protection, Inc. and is described by Margot et al. (1998). It is a broad-spectrum foliar fungicide registered on fruits, vegetables, turf, and ornamentals. Trade names include Compass, Flint, and Stratego[1].

Chemical property

It exists as a white powder, m.p. 73°c, v.p. 3.4 × 10−6 Pa (25°C), w.s. 0.61 ppm (25°C), log P4.5, HLC 2.3 × 10−3 Pa m3 mol−1. Trifloxystrobin has two oxime linkages, each showing geometrical isomerism. The commercial compound is the E, E-isomer. The hydrolysis half-life is 11.4 weeks at pH 7 and 27 hr at pH 9. It is stable at pH 5.

Mechanism of action and uses

Trifloxystrobin (TFS), as a strobilurin fungicide, binds to the region (Qo) of complex III and stops respiratory activities in mitochondria. As a result, it interrupts the vital energy cycle in fungi by inhibiting the generation of adenosine triphosphate in fungi5. TFS is widely used in rice, cereals, fruits, vegetables, grapes, potatoes, and soybeans to combat sheath blight and rice blast fungus[2].

Environmental Fate and Toxicity

Strobilurin-type fungicides such as TFS can cause environmental pollution due to their intense use, as well as their ability to remain in water, air, soil, and products after being applied to plants. Despite all its advantages, TFS has a slow rate of hydrolysis in non-acidic environments, so its half-life can be several years as Trifloxystrobin acid (TFSA). In addition, TFSA, the major metabolite of TFS, is more soluble in water and is more environmentally hazardous than TFS.

Trifloxystrobin has a low acute toxicity to birds. Prolonged dietary exposure at 320 ppm (bobwhite quail) or 500 ppm had no effects on health or reproduction. It is highly toxic to fish and several kinds of aquatic invertebrates. The LC50 to mysid shrimp is 9 ppb. Bioconcentration in fish is limited, probably due to rapid metabolism and depuration. Trifloxystrobin is rapidly degraded in surface water by microbial action with a half-life of a few hours. The photolysis half-life in water is 31.5 hr, with the initial reaction being E to Z isomerization. Trifloxystrobin binds firmly to soil particles (log Koc 1642–3745 in five soils), and its half-life in soils in field studies ranges from 1.9 to 16 (mean 5.4) days, indicating a low environmental persistence and leaching potential.

[1] Trifloxystrobin - an overview | ScienceDirect Topics https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/trifloxystrobin

[2] Oksal Macar. “Acute multiple toxic effects of Trifloxystrobin fungicide on Allium cepa L.” Scientific Reports (2022): 15216.

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