Emamectin benzoate (Proclaim^®) is a macrocyclic lactone semi-synthetic derivative of the avermectins. It is a mixture of at least 90% avermectin B1a benzoate (MAB1a) and at most 10% MAB1b salts [1Sun Y., et al. Bioaccumulation and elimination of avermectin B1a in the earthworms (Eisenia foetida) Chemosphere 2005 ;  60 : 699-704 [cross-ref]

Cliquez ici pour aller à la section Références]. The aim of this study is to investigate the plasma and kidney distribution of EMB in rats by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) and to evaluate the protective effects of vitamin C against toxicity of this biopesticide after a subacute toxicity study.

Male rats (n=21) were allocated into 3 groups of seven each: group I served as control rats; group II was given daily EMB at dose of 10mg/kg b.w. by gavage; group III received EMB (10mg/kg b.w.) and were co-administered with vitamin C intraperitoneally (200mg/kg/day) during 28days. Rats were followed-up for an additional 14 day-period to detect delayed occurrence or persistence of toxic effects. The residual concentrations of emamectin benzoate mixture B1a and B1b were determined in control, EMB, and EMB+VitC groups. Plasma and tissue homogenates were pretreated by protein precipitation with acetonitrile. In plasma samples at 14, 21, 28 and 42days of experiment and in kidneys at 28 and 42days of experiment, B1a and B1b concentrations were determined.

A decrease in body weight, absolute and relative kidney weights in EMB-treated rats and a significant increase in EMB +VitC group, after 28 and 42days of experiment, were observed. Emamectin B1a and B1b were found in all plasma samples of EMB and EMB+VitC rats in a time-dependent manner at 14days [EMB group (B1a: 531.95±98.31; B1b: 20.25±10.71) and EMB+VitC (B1a: 436.70±200.39; B1b: 15.12±2.97)], 21days [EMB group (B1a: 566.29±103.91; B1b: 19.73±3.00) and EMB+VitC group (B1a: 315.97±73.72; B1b: 16.02±4.00)] and 28days of treatment [EMB group (B1a: 626.35±159.32; B1b: 23.03±8.19) and EMB+VitC group (B1a: 368.50±152.22; B1b: 14.88±7.28)]. However, those concentrations were higher in the EMB-treated group when compared with the EMB+VitC group. Moreover, at 42days, there was no more residue detectable in the plasma of all treated rats. In EMB-treated rats, the drug kidney concentrations were significantly lower in EMB+VitC compared with EMB-treated rats at 28days [EMB group (B1a: 24.98±1.85; B1b: 3.63±0.34) and EMB+VitC (B1a: 14.14±1.24; B1b: 1.26±0.29)] and 42days post-treatment [EMB group (B1a: 0.87±0.30; B1b: 0.04±0.01) and EMB+VitC (B1a: 0.31±0.15; B1b: 0.01±0.00)]. Elevated concentrations of residues in plasma and kidneys of EMB-treated rats compared to those in EMB+Vit C-treated rats suggest an ameliorative effect of vitamin C.

EMB was widely distributed in rat plasma and kidneys and its concentrations in kidney increased in a time-dependent manner. Vitamin C, when administered at moderate doses and maintained for a long period, could reduce the accumulation of EMB in plasma and kidneys.