Dimethenamid promotes oxidative stress and apoptosis leading to cardiovascular, hepatic, and pancreatic toxicities in zebrafish embryo.

Dimethenamid, one of the acetamide herbicides, is widely used on soybeans and corns to inhibit weed growth. Although other acetamide herbicides have been reported to have several toxicities in non-target organisms including developmental toxicity, the toxicity of dimethenamid has not yet been studied. In this research, we utilized the zebrafish animal model to verify the developmental toxicity of dimethenamid. It not only led to morphological abnormalities in zebrafish larvae but also reduced their viability. ROS production and inflammation responses were promoted in zebrafish larvae. Also, uncontrolled apoptosis occurred when the gene expression level related to the cell cycle and apoptosis was altered by dimethenamid. These changes resulted in toxicities in the cardiovascular system, liver, and pancreas are observed in transgenic zebrafish models including fli1a:EGFP and L-fabp:dsRed;elastase:GFP. Dimethenamid triggered morphological defects in the heart and vasculature by altering the mRNA levels related to cardiovascular development. The liver and pancreas were also damaged through not only the changes of their morphology but also through the dysregulation in their function related to metabolic activity. This study shows the developmental defects induced by dimethenamid in zebrafish larvae and the possibility of toxicity in other non-target organisms.

Potential secondary metabolite from Indonesian Actinobacteria (InaCC A758) against Mycobacterium tuberculosis.

OBJECTIVES: This study explored Indonesian Actinobacteria which were isolated from Curcuma zedoaria endophytic microbes and mangrove ecosystem for new antimycobacterial compounds. MATERIALS AND METHODS: Antimycobacterial activity test was carried out against Mycobacterium tuberculosis H37Rv. Chemical profiling of secondary metabolite using Gas Chromatography-Mass Spectroscopy (GC-MS) and High Resolution-Mass Spectroscopy (HR-MS) was done to the ethyl acetate extract of active strain InaCC A758. Molecular taxonomy analysis based on 16S rRNA gene and biosynthetic gene clusters analysis of polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) from InaCC A758 have been carried out. Bioassay guided isolation of ethyl acetate extract was done, then structural elucidation of active compound was performed using UV-Vis, FT-IR, and NMR spectroscopy methods. RESULTS: The chemical profiling using HR-MS revealed that InaCC A758 has the potential to produce new antimycobacterial compounds. The 16S rRNA gene sequencing showed that InaCC A758 has the closest homology to Streptomyces parvus strain NBRC 14599 (99.64%). In addition, InaCC A758 has NRPS gene and related to S. parvulus (92% of similarity), and also PKS gene related to PKS-type borrelidin of S. rochei and S. parvulus (74% of similarity). Two compounds with potential antimycobacterial were predicted as 1) Compound 1, similar to dimethenamid (C12H18ClNO2S; MW 275.0723), with MIC value of 100 µg/ml, and 2) Compound 2, actinomycin D (C62H86N12O16; MW 1254.6285), with MIC value of 0.78 µg/ml. CONCLUSION: Actinomycin D has been reported to have antimycobacterial activity, however the compound has been predicted to resemble dimethenamid had not been reported to have similar activity.

Evaluation of confirmatory data following the Article 12 MRL review for dimethenamid-P.

The applicant BASF SE submitted a request to the competent national authority in Germany to evaluate the confirmatory data that were identified for dimethenamid-P in the framework of the maximum residue level (MRL) review under Article 12 of Regulation (EC) No 396/2005 as not available. The data gap refers to the submission of a plant metabolism study investigating the fate of dimethenamid-P following foliar treatment with a short preharvest interval (PHI) in a leafy or bulb vegetable crop. The confirmatory data requirement is considered sufficiently addressed according to the conclusions of the peer review, which, based on available metabolism studies, proposed to modify the existing enforcement and risk assessment residue definitions in all plant commodities, by including additional dimethenamid-P metabolites ((2RS)-3-(2-{(2,4-dimethylthiophen-3-yl)[(2S)-1-methoxypropan-2-yl]amino}-2-oxoethanesulfinyl)-2-hydroxypropanoic acid (M30) and (2RS)-3-[(2-{(2,4-dimethylthiophen-3-yl)[(2S)-1-methoxypropan-2-yl]amino}-2-oxoethyl)sulfanyl]-2-hydroxypropanoic acid (M26). The residue data of metabolites M26 and M30 are currently not available for all authorised uses assessed in the MRL review. Should risk managers decide amending residue definitions, the existing EU MRLs would need to be revised accordingly. The consumer exposure as calculated by the MRL review was updated in two scenarios, using the existing and the new toxicological reference values as derived by the peer review. For the crops under consideration (spring onions, lettuce, escarole and herbs), indicative conversion factors were applied to account for possible metabolite burden. No consumer intake concerns were identified.

Peer review of the pesticide risk assessment of the active substance dimethenamid-P.

The conclusions of EFSA following the peer review of the initial risk assessments carried out by the competent authorities of the rapporteur Member State Germany and co-rapporteur Member State Bulgaria for the pesticide active substance dimethenamid-P and the assessment of applications for maximum residue levels (MRLs) are reported. The context of the peer review was that required by Commission Implementing Regulation (EU) No 844/2012. The conclusions were reached on the basis of the evaluation of the representative uses of dimethenamid-P as a herbicide on annual monocotyledonous and dicotyledonous weeds in winter oilseed rape, maize, sweet corn, soya bean, sunflower and sugar beet. The reliable end points, appropriate for use in regulatory risk assessment and the proposed MRLs, are presented. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.

Biotransformation of Dimethenamid-P by the basidiomycete Irpex consors.

Twenty-nine basidiomycetes were screened in surface and liquid cultures for their capability to biotransform the chloroacetamide herbicide Dimethenamid-P (DMTA-P). The basidiomycete Irpex consors converted 70% of the herbicide (0.5 g L-1 DMTA-P) in liquid cultures within 6 days, applying a minimal medium under non-ligninolytic conditions. Nine transformation products of DMTA-P were identified by liquid chromatography-mass spectrometry analysis of the culture supernatants. The four main metabolites were isolated and subjected to GC-MS analysis and NMR spectroscopy. The analyses revealed that the thiophene ring was oxidized at three different positions. Metabolite M1 was identified as the S-oxide, which was isolable and relatively stable at room temperature. In metabolite M2, one methyl substituent of the thiophene ring was hydroxylated. The two metabolites M3A and M3B were diastereomers, but fully separated by HPLC. Here, oxidation of the aromatic CH carbon resulted in prototropic rearrangement to an αß-unsaturated thiolactone. None of the three major metabolites of DMTA-P has been described before.