Napropamide (Napropamid)

Napropamide

THE TITLE COMPOUND [SYSTEMATIC NAME: N,N-diethyl-2-(naphthalen-1-yl-oxy)propanamide], C17H21NO2, crystallizes with two independent mol-ecules in the asymmetric unit in which the dihedral angles between the naphthalene ring systems and the amide groups are 88.1 (9) and 88.7 (3)～. Four C-H?O hydrogen bonds stabilize the crystal structure.

Enantioselective phytotoxicity and bioacitivity of the enantiomers of the herbicide napropamide

Enantioselectivity of chiral pesticide enantiomers should be taken into consideration in pesticide application and environmental risk assessment. The phytotoxicity of the enantiomers of napropamide to cucumber, soybean, and the bioactivity to the target weeds Poa annua and Festuca arundinacea have been studied in this work. To the nontarget crops, the influences of napropamide on the root, shoot, fresh weight, chlorophyll, superoxide dismutase (SOD) and catalase (CAT) activities and membrane lipid peroxides have been studied. (-)-Napropamide was more toxic than the racemate and (+)-napropamide to soybean and cucumber in terms of root, shoot and fresh weight. The content of chlorophyll was not affected by napropamide. The impacts on the activities of SOD, CAT and membrane lipid peroxides showed that napropamide could induce the oxidative stress and rac-napropamide caused a stronger oxidative damage to cucumber and soybean than (-)-napropamide and (+)-napropamide. For the target weeds, the influences of napropamide on root, shoot and fresh weight have been studied. (-)-Napropamid was more active to P. annua, while rac-napropamide was more active to F. arundinacea. To reduce environmental pollution and improve the effectiveness of chiral pesticide, single enantiomer should be developed and produced. This work may provide evidence for developing optical pure product.

Enantioselectivity and allelopathy both have effects on the inhibition of napropamide on Echinochloa crus-galli

Napropamide is a chiral acetamide herbicide commonly applied to control Echinochloa crus-galli in maize. The inhibition effect may be enantioselective for Echinochloa crus-galli and maize. It may also be affected by the potential allelopathy at field condition. To investigate this, we have examined the inhibition effect of napropamide on Echinochloa crus-galli mono-cultured or co-cultured with maize at field conditions. Our results on morphology, physiology, chlorophyll content and chlorophyll fluorescence suggest that R-napropamide has stronger inhibitory effect than Rac-napropamide and S-napropamide on Echinochloa crus-galli, while none of them affects maize. We found that both glutathione-S-transferase (GST) genes and oxidative enzymes (superoxide dismutase, malondialdehyde) played roles in the inhibition. Accumulations of napropamide in Echinochloa crus-galli were more prominent in roots than in shoots, and no enantioselectivity was found in medium dissipation. We have observed relative allelopathy when applying napropamide to Echinochloa crus-galli co-cultured with maize. The results warrant further field studies on the enantioselectivity and allelopathy of herbicides.

Accumulation and residue of napropamide in alfalfa (Medicago sativa) and soil involved in toxic response

Napropamide belongs to the amide herbicide family and widely used to control weeds in farmland. Intensive use of the herbicide has resulted in widespread contamination to ecosystems. The present study demonstrated an analysis on accumulation of the toxic pesticide napropamide in six genotypes of alfalfa (Medicago sativa), along with biological parameters and its residues in soils. Soil was treated with napropamide at 3 mg kg(-1) dry soil and alfalfa plants were cultured for 10 or 30 d, respectively. The maximum value for napropamide accumulation is 0.426 mg kg(-1) in shoots and 2.444 mg kg(-1) in roots. The napropamide-contaminated soil with alfalfa cultivation had much lower napropamide concentrations than the control (soil without alfalfa cultivation). Also, the content of napropamide residue in the rhizosphere was significantly lower than that in the non-rhizosphere soil. M. sativa exposed to 3 mg kg(-1) napropamide showed inhibited growth. Further analysis revealed that plants treated with napropamide accumulated more reactive oxygen species (O(2)(-) and H(2)O(2)) and less amounts of chlorophyll. However, not all cultivars showed oxidative injury, suggesting that the alfalfa cultivars display different tolerance to napropamide.

Enantiomer/stereoisomer-specific residues of metalaxyl, napropamide, triticonazole, and metconazole in agricultural soils across China

In this study, the residual status of four chiral pesticides including metalaxyl, napropamide, triticonazole, metconazole, and their enantiomers/stereoisomers were investigated in agricultural soils across China. The levels in the soils were detected as non-detected (n.d.)-16.67 ng/g for metalaxyl with a median of 0.14 ng/g; 0.004-32.99 ng/g for napropamide with a median of 0.29 ng/g; n.d.-207.39 ng/g for triticonazole with a median of 1.29 ng/g; and n.d.-71.83 ng/g for metconazole with a median of 1.03 ng/g, respectively. Enantiomer/stereoisomer-specific residues were observed for metalaxyl and triticonazole. R-Metalaxyl and R-triticonazole were identified as the major enantiomers in the soils for the two pesticides. There was no obvious enantioselective residue for napropamide in most of the soils. As for metconazole, metconazole-1 and metconazole-4 were identified as the major stereoisomers in the soils. These results suggest that enantiomer/stereoisomer-specific risk should be considered when assessing the ecological safety of these pesticides in soils.