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PubMed1983

Hypolipidemia and peroxisome proliferation induced by phenoxyacetic acid herbicides in rats.

Male Wistar rats were treated daily by gavage with two phenoxy herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D)(100-200 mg/kg body wt) and 4-chloro-2-methylphenoxyacetic acid (MCPA) (100-200 mg/kg body wt), and with the chemically different glyphosate N-phosphonomethyl glycine (300 mg/kg body wt) 5 days per week for 2 weeks. A hypolipidemic drug, clofibrate [ethyl-2-(4-chlorophenoxy)-2-methylpropionate], which is structurally related to phenoxy acids, was used as a positive control (200 mg/kg body wt). 2,4-D and MCPA had several effects similar to those of clofibrate: all three compounds induced proliferation of hepatic peroxisomes, decreased serum lipid levels, and increased hepatic carnitine acetyltransferase and catalase activities. 2,4-D and MCPA, but not clofibrate, decreased lipoprotein lipase activity in the adipose tissue to about a third of the control value but did not change the lipoprotein lipase activity in the heart muscle. The data suggest that these compounds cause hypolipidemia not by enhancing the storage of peripheral lipids in adipose tissue but by preferentially increasing lipid utilization in the liver. Glyphosate caused no peroxisome proliferation or hypolipidemia, suggesting that these effects are associated with the structural similarity between phenoxy acid herbicides and clofibrate.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2005

The evaluation of different sorbents for the preconcentration of phenoxyacetic acid herbicides and their metabolites from soils.

A procedure using alkaline extraction, solid-phase extraction (SPE) and HPLC is developed to analyze the polar herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) together with their main metabolites in soils. An ion-pairing HPLC method is used for the determination as it permits the baseline separation of these highly polar herbicides and their main metabolites. The use of a highly cross-linked polystyrene-divinylbenzene sorbent (PS-DVB) gives the best results for the analysis of these compounds. This sorbent allows the direct preconcentration of the analytes at the high pH values obtained after quantitative alkaline extraction of the herbicides from soil samples. Different parameters are evaluated for the SPE preconcentration step. The high polarity of the main analytes of interest (2,4-D and MCPA) makes it necessary to work at low flow rates (< or =0.5 mL min(-1)) in order for these compounds to be retained by the PS-DVB sorbent. A two stage desorption from the SPE sorbent is required to obtain the analytes in solvents that are appropriate for HPLC determination. A first desorption with a 50:50 methanol:water mixture elutes the most polar analytes (2,4-D, MCPA and 2CP). The second elution step with methanol permits the analysis of the other phenol derivatives. The humic and fulvic substances present in the soil are not efficiently retained by PS-DVB sorbents at alkaline pH's and so do not interfere in the analysis. This method has been successfully applied in the analysis of soil samples from a golf course treated with a commercial product containing esters of 2,4-D and MCPA as the active components.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2005

Radiolytic degradation of herbicide 4-chloro-2-methyl phenoxyacetic acid (MCPA) by gamma-radiation for environmental protection.

Reversed-phase HPLC determination of the herbicide MCPA and its products of radiolytic degradation has been optimized. The radiolytic degradation was carried out using gamma-irradiation and was optimized in terms of irradiation dose and pH of irradiated MCPA solution. Decomposition of 100 ppm MCPA in pure solutions required irradiation with a 3 kGy dose. The main products of irradiation in the dose range up to 10-kGy were various phenolic compounds and carboxylic acids. The developed method was applied for treatment of industrial waste from production of MCPA. The 10-kGy dose was needed for decomposition of 500 ppm of MCPA in the industrial waste samples; however, the presence of stoichiometric amount of hydrogen peroxide in the irradiated waste allowed a 50% reduction of the gamma-irradiation dose. Despite complete decomposition of MCPA in the industrial waste, in order to reduce the toxicity of irradiated waste, measured by the Microtox bioluminescence test, higher than a 10 kGy irradiation dose was needed.

2-Methyl-4-chlorophenoxyacetic Acid↗
PubMed2001

Carboxylic acids and skeletal muscle chloride channel conductance: effects on the biological activity induced by the introduction of an aryloxyalkyl group alpha to the carboxylic function of 4-chloro-phenoxyacetic acid.

2-(4-Chloro-phenoxy)propanoic and 2-(4-chloro-phenoxy)butanoic acids are compounds known to block chloride membrane conductance in rat striated muscle by interaction with a specific receptor. In the present study, a series of chiral analogues has been prepared and tested to evaluate the influence of a second aryloxy moiety introduced in the side-chain at a variable distance from the stereogenic centre. The results show that this chemical modification is detrimental for biological activity which, however, is increased by lengthening the alkyl chain up to three methylenic groups, then decreases to remain constant in the next analogues of the series. A possible explanation for this is proposed on the basis of steric effects and/or different approach of the molecules to the receptor.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2003

Toxicity of chlorinated phenoxyacetic acid herbicides in the experimental eukaryotic model Saccharomyces cerevisiae: role of pH and of growth phase and size of the yeast cell population.

The inhibitory effect of the herbicides 2-methyl-4-chlorophenoxyacetic acid (MCPA) and 2,4-dichlorophenoxyacetic acid (2,4-D) in Saccharomyces cerevisiae growth is strongly dependent on medium pH (range 2.5-6.5). Consistent with the concept that the toxic form is the liposoluble undissociated form, at values close to their pK(a) (3.07 and 2.73, respectively) the toxicity is high, decreasing with the increase of external pH. In addition, the toxicity of identical concentrations of the undissociated acid form is pH independent, as observed with 2,4-dichlorophenol (2,4-DCP), an intermediate of 2,4-D degradation. Consequently, at pH values above 3.5 (approximately one unit higher than 2,4-D pK(a)), 2,4-DCP becomes more toxic than the original herbicide. A dose-dependent inhibition of growth kinetics and increased duration of growth latency is observed following sudden exposure of an unadapted yeast cell population to the presence of the herbicides. This contrasts with the effect of 2,4-DCP, which essentially affects growth kinetics. Experimental evidences suggest that the acid herbicides toxicity is not exclusively dependent on the liposolubility of the toxic form, as may essentially be the case of 2,4-DCP. An unadapted yeast cell population at the early stationary-phase of growth under nutrient limitation is significantly more resistant to short-term herbicide induced death than an exponential-phase population. Consequently, the duration of growth latency is reduced, as observed with the increase of the size of the herbicide stressed population. However, these physiological parameters have no significant effect either on growth kinetics, following growth resumption under herbicide stress, or on the growth curve of yeast cells previously adapted to the herbicides, indicating that their role is exerted at the level of cell adaptation.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1998

Phenoxyacetic acids: separation and quantitative determination.

The various chromatographic methods suitable for the separation and quantitative determination of phenoxyalkyl acid herbicides in environmental samples are reviewed, with special emphasis being placed on sample preparation methods such as liquid-liquid, solid-phase and supercritical fluid extractions. Techniques are classified (high-performance liquid chromatography, gas-liquid chromatography, capillary zone electrophoresis, micellar electrokinetic chromatography) and discussed separately. The advantages and disadvantages of the various preparation and separation methods and their combinations are evaluated.

Chromatography, Gas↗