Novel lipophilic analogues from 2,4-D and Propanil herbicides: Biological activity and kinetic studies

This work describes the synthesis of new lipophilic amides and esters analogues of classical organochlorides herbicides by incorporation of long-chains from fatty acids and derivatives. The new fatty esters and amides were synthesized in 96-99% and 80-89% yields, respectively. In general, all compounds tested showed superior in vitro activity than commercial herbicides against growth L. sativa and A. cepa, in ranges 86-100% of germinative inhibition. The target compounds showed, significantly more susceptible towards acid hydrolysis than 2,4-dichlorophenoxyacetic acid (2,4-D). The kinetic and NMR studies showed that the incorporation of lipophilic chains resulted in a decrease in half-life time of new herbicides compounds (1.5 h) than 2,4-D (3 h). These findings suggest the synthesis of new lipophilic herbicides as potential alternative to traditional formulations, by incorporation of long fatty alkyl chains in the molecular structure of 2,4-D, resulting in superior in vitro herbicidal activity, best degradation behavior and more hydrophobic derivatives.

A psbA mutation (Val219 to Ile) causes resistance to propanil and increased susceptibility to bentazon in Cyperus difformis

BACKGROUND

Propanil-resistant (R) Cyperus difformis populations were recently confirmed in California rice fields. To date, propanil resistance in other weed species has been associated with enhanced aryl acylamidase (AAA)-mediated propanil conversion into 3,4-dichloroaniline. Our objectives were to determine the level of propanil resistance and cross-resistance to other PSII inhibitors in C. difformis lines, and to elucidate the mechanism of propanil resistance.

RESULTS

The propanil-R line had a 14-fold propanil resistance and increased resistance to bromoxynil, diuron and metribuzin, but not to atrazine. The R line, however, displayed a fourfold increased susceptibility to bentazon. Interestingly, susceptible (S) plants accumulated more 3,4-dichloroaniline and were more injured by propanil and carbaryl (AAA-inhibitor) applications than R plants, suggesting that propanil metabolism is not the resistance mechanism. psbA gene sequence analysis indicated a valine-219-isoleucine (Val219 Ile) amino acid exchange in the propanil-R chloroplast D1 protein.

CONCLUSION

The D1 Val219 Ile modification in C. difformis causes resistance to propanil, diuron, metribuzin and bromoxynil but increased susceptibility to bentazon, suggesting that the Val219 residue participates in binding of these herbicides. This is the first report of a higher plant exhibiting target-site propanil resistance. Tank mixing of bentazon and propanil, where permitted, can control both propanil-R and propanil-S C. difformis and prevent the spread of the resistant phenotype. © 2016 Society of Chemical Industry.

Are Portuguese Echinochloa spp. populations still susceptible to propanil?

Propanil is the most important herbicide for rice weed management both at world and national level. Rice growers complains of poor control of Echinochloa was monitored in Mondego and Sorraia river valleys, Portugal. Seed samples were collected from the affected area and tested. After the first screening of 37 populations, the sensitivity of six Echinochloa spp. populations to propanil was assessed in a growth chamber dose response study (with seven rates: 0- 7200 g a.i. ha(-1)). Fresh weight was assessed 21 days after treatment and data was analysed using non-linear regression analysis and sensitivity indices (SI = ED80, less sensitive/ ED80, most sensitive) calculated for the two regions surveyed. The rates of 50% of plant growth inhibition (ED50) was calculated from the fitted equations. Four populations where confirmed susceptible with ED50 values ranging from 89 to 1866 g a.i. ha(-1). Two other populations presented ED50 values of 6538 and 9536 g a.i. ha(-1). Mondego and Sorraia SI were 2.35 and 53.55 respectively. The pattern of propanil use in the two regions could explain the higher sensitivity of Mondego populations compared to Sorraia populations. The response to a single dose Petri dish bioassay (360 g a.i. L(-1)) was similar among the six populations, denoting that this method was not so sensitive as the whole plant assay to discriminate between Echinochloa spp. populations. Further studies are needed with more doses and populations since this method allows for an answer within six days, compared with 41 days with the whole plant bioassay.

Propanil and swep inhibit 4-coumarate:CoA ligase activity in vitro

4-Coumarate:CoA ligase (4CL, EC 6.2.1.12) in the phenylpropanoid pathway in plants has attracted interest as a novel target for developing effective plant growth inhibitors (PGIs). In a previous study in which the 4CL inhibitory activity of 28 existing herbicides was investigated using an optimized in vitro screening assay, 4CL activity was found to be strongly inhibited by propanil and swep at 100 microM. Here, further experimental evidence is provided to substantiate the previous result. Using 4-coumaric acid as substrate, tobacco 4CL activity was inhibited by propanil or swep in a concentration-dependent manner, with 50% inhibition concentrations (I(50)) of 39.6 and 6 microM respectively. These herbicides also exhibited uncompetitive inhibition towards 4-coumaric acid. Furthermore, 4CLs from several plant species were inhibited by the herbicides within a range from 1 to 50 microM. It is proposed that these herbicides have another site of action as a result of the inhibition of 4CL in the phenylpropanoid pathway, and this enzyme represents a new target site for the development of PGI.

Propanil exposure induces delayed but sustained abrogation of cell-mediated immunity through direct interference with cytotoxic T-lymphocyte effectors

The postemergent herbicide propanil (PRN ; also known as 3,4-dichloropropionanilide) is used on rice and wheat crops and has well-known immunotoxic effects on various compartments of the immune system, including T-helper lymphocytes, B lymphocytes, and macrophages. It is unclear, however, whether PRN also adversely affects cytotoxic T lymphocytes (CTLs) , the primary (1 degrees ) effectors of cell-mediated immunity. In this study we examined both the direct and indirect effects of PRN exposure on CTL activation and effector cell function to gauge its likely impact on cell-mediated immunity. Initial experiments addressed whether PRN alters the class I major histocompatibility complex (MHC) pathway for antigen processing and presentation by antigen-presenting cells (APCs) , thereby indirectly affecting effector function. These experiments demonstrated that PRN does not impair the activation of CTLs by PRN-treated APCs. Subsequent experiments addressed whether PRN treatment of CTLs directly inhibits their activation and revealed that 1 degrees alloreactive CTLs exposed to PRN are unimpaired in their proliferative response and only marginally inhibited in their lytic activity. Surprisingly, secondary stimulation of these alloreactive CTL effectors, however, even in the absence of further PRN exposure, resulted in complete abrogation of CTL lytic function and a delayed but significant long-term effect on CTL responsiveness. These findings may have important implications for the diagnosis and clinical management of anomalies of cell-mediated immunity resulting from environmental exposure to various herbicides and other pesticides.

Modeling and predicting stress-induced immunosuppression in mice using blood parameters

Previous studies have shown that the area under the corticosterone concentration vs. time curve (AUC) can be used to model and predict the effects of restraint stress and chemical stressors on a variety of immunological parameters in the mouse spleen and thymus. In order to complete a risk assessment parallelogram, similar data are needed with blood as the source of immune system cells, because this is the only tissue routinely available from human subjects. Therefore, studies were conducted using treatments for which the corticosterone AUC values are already known: exogenous corticosterone, restraint, propanil, atrazine, and ethanol. Immunological parameters were measured using peripheral blood from mice treated with a series of dosages of each of these agents. Flow cytometry was used to quantify MHC II, B220, CD4, and CD8 cells. Leukocyte and differential counts were done. Spleen cell number and NK cell activity were evaluated to confirm similarity to previous studies. Immune parameter data from mouse blood indicate that MHC II expression has consistent quantitative relationships to corticosterone AUC values, similar to but less consistent than those observed in the spleen. Other immune parameters tended to have greater variability in the blood than in the spleen. The pattern observed in the spleen in which the chemical stressors generally produced very similar effects as noted for restraint stress (at the same corticosterone AUC values) was not observed for blood leukocytes. Nevertheless, MHC class II expression seems to provide a reasonably consistent indication of stress exposure in blood and spleen.

Cyanobacteria in Uruguayan rice fields: diversity, nitrogen fixing ability and tolerance to herbicides and combined nitrogen

It has been established that cyanobacteria play a vital role in the maintenance of flooded rice field fertility. To evaluate the potential use of nitrogen-fixing cyanobacteria as a natural biofertilizer for rice in Uruguay, the diversity, abundance and nitrogen fixing ability of these microorganisms were studied in the field and in the laboratory. The effect of urea fertilization on population density and diversity of heterocystous cyanobacteria was determined on a 3-year assay. The highest number of cyanobacteria, 1.6x10(4) CFU x m(-2), was found at the control 8 weeks after flooding. About 90% of the heterocystous cyanobacteria found in both treatments belong to the genera Nostoc and Anabaena. Maximal nitrogenase activity was reached after 12 weeks of flooding in both treatments, with an average of about 20 micromol C2H4 x m(-2) x h(-1). To improve the understanding of the environmental factors that can limit nitrogenase activity in rice fields, two of the most abundant cyanobacteria isolates were tested for tolerance to combined nitrogen and two herbicides. In both isolates 0.2 mM ammonium inhibited nitrogenase activity after 24 h of culture. The addition of field-recommended doses of quinclorac and propanil affected oxygen photoevolution but nitrogenase activity was only inhibited by propanil.

Propanil inhibits tumor necrosis factor-alpha production by reducing nuclear levels of the transcription factor nuclear factor-kappab in the macrophage cell line ic-21

Tumor necrosis factor-alpha (TNF-alpha) is an essential proinflammatory cytokine whose production is normally stimulated by bacterial cell wall components, such as lipopolysaccharide (LPS), during an infection. Macrophages stimulated with LPS in vitro produce several cytokines, including TNF-alpha. LPS-stimulated primary mouse macrophages produced less TNF-alpha protein and message after treatment with the herbicide propanil (Xie et al., Toxicol. Appl. Pharmacol. 145, 184-191, 1997). Nuclear factor-kappaB (NF-kappaB) tightly regulates TNF-alpha transcription. Therefore, as a step toward understanding the mechanism of the effect of propanil on TNF-alpha transcription, IC-21 cells were transfected with a TNF-alpha promoter-luciferase construct, and the effect of propanil on luciferase activity was measured. Cells transfected with promoter constructs containing a kappaB site showed decreased luciferase activity relative to controls after propanil treatment. These observations implicated NF-kappaB binding as an intracellular target of propanil. Further studies demonstrated a marked reduction in the nuclear levels of the stimulatory p65 subunit of NF-kappaB after propanil treatment, as measured by fluorescence confocal microscopy and Western blot analysis. The p50 subunit of NF-kappaB was not found to be reduced after propanil exposure by Western blot. Electrophoretic mobility gel shift assays showed decreased DNA binding of both p65/p50 heterodimers and p50/p50 homodimers to the kappaB3 site of the TNF-alpha promoter of propanil-treated cells. The marked reduction in nuclear p65/p50 NF-kappaB levels and diminished binding to the TNF-alpha promoter in propanil-treated cells are consistent with reduced TNF-alpha levels induced by LPS.

Alteration of macrophage cytotoxicity through endogenous interferon and tumor necrosis factor alpha induction by propanil

The effect of propanil on mouse peritoneal macrophages (m phi) was measured by determining cytotoxicity via the P815 cell line, which is resistant to tumor necrosis factor alpha (TNF-alpha). Although control animals showed a typical pattern of requiring both interferon (IFN)-gamma and lipopolysaccharide (LPS) for m phi activation, m phi from propanil-treated animals were cytotoxic when induced with LPS alone. This suggested that propanil influenced endogenous IFN levels. This was confirmed by the abrogation of cytotoxicity upon addition of anti-IFN to the cultures. When cells were assayed for IFN transcript, mRNA in resident m phi was present in higher concentrations in propanil-treated animals. IFN mRNA was present in even higher concentrations in m phi from propanil-treated animals after 30 min of culture with LPS, whereas control m phi required 4 hr in culture with LPS to produce similar levels. IFN protein levels were also higher in propanil-treated m phi after culture in the presence of LPS. Thus, propanil induces increased levels of endogenous IFN which probably works in conjunction with LPS to induce P815 cytotoxicity. Because of the known influence IFN has on the increased secretion of TNF-alpha, we tested the tumoricidal activity of m phi from propanil-treated animals against TNF-alpha-sensitive cell lines. When using WEHI-164 or L929 cells, m phi from propanil-treated animals revealed tumoricidal activity with just the addition of LPS or IFN-gamma. This implies that the additional endogenous levels of IFN, combined with other propanil-induced effects, caused increased secretion of TNF-alpha from m phi.

Electrophoretic pattern of red blood cell catechol-o-methyltransferase in schizophrenia and manic-depressive illness

Human red blood cell (RBC) catechol-O-methyltransferase (COMT) was analyzed by polyacrylamide gel electrophoresis (PAGE). One major enzyme band (B) is observed after electrophoresis. In addition, a minor band (A) of COMT activity comprising no more than 25% of the total activity, is also detectable. The rate of migration during electrophoresis of both bands of RBC COMT was the same in manic depressive, schizophrenic, and normal individuals. These results did not reveal genetic variations in the COMT molecule among these three groups. Furthermore, when total RBC COMT was measured there were no statistically significant differences between schizophrenic, manic-depressive, and control individuals.

[Reaction of soil microflora to propanide treatment]

Propanide, a herbicide, is hydrolyzed in the soil into 3,4-dichloroaniline and propionic acid. The amount of microorganisms resistant to propanide and 3,4-dichloroaniline increases when the herbicide is added to the soil, and then decreases when these compounds disappear from the soil.