Browsing by Author "Silva, A. M. S."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Electrochemical and spectroscopic studies of the oxidation mechanism of the herbicide propanilPublication . Garrido, E. Manuela; Lima, J. L. F. C.; Delerue-Matos, Cristina; Borges, F.; Silva, A. M. S.; Piedade, J. A. P.; Oliveira-Brett, A. M.Electrochemical oxidation of propanil in deuterated solutions was studied by cyclic, differential pulse, and square wave voltammetry using a glassy carbon microelectrode. The oxidation of propanil in deuterated acid solutions occurs at the nitrogen atom of the amide at a potential of +1.15 V vs Ag/ AgCl. It was also found that, under the experimental conditions used, protonation at the oxygen atom of propanil occurs, leading to the appearance of another species in solution which oxidizes at +0.60 V. The anodic peak found at +0.79 V vs Ag/AgCl in deuterated basic solutions is related to the presence of an anionic species in which a negative charge is on the nitrogen atom. The electrochemical data were confirmed by the identification of all the species formed in acidic and basic deuterated solutions by means of NMR spectroscopy. The results are supported by electrochemical and spectroscopic studies of acetanilide in deuterated solutions.
- Electrochemical oxidation of propanil and related N-substituted amidesPublication . Garrido, E. Manuela; Lima, J. L. F. C.; Delerue-Matos, Cristina; Borges, F.; Silva, A. M. S.; Oliveira-Brett, A. M.The electrochemical behaviour of propanil and related N-substituted amides (acetanilide and N,N-diphenylacetamide) was studied by cyclic and square wave voltammetry using a glassy carbon electrode. Propanil has been found to have chemical stability under the established analytical conditions and showed an oxidation peak at +1.27V versus Ag/AgCl at pH 7.5. N,N-diphenylacetamide has a higher oxidation potential than the other compounds of +1.49V versus Ag/AgCl. Acetanilide oxidation occurred at a potential similar to that of propanil, +1.24V versus Ag/AgCl. These results are in agreement with the substitution pattern of the nitrogen atom of the amide. A degradation product of propanil, 3,4-dichloroaniline (DCA), was also studied, and showed an oxidation peak at +0.66V versus Ag/AgCl. A simple and specific quantitative electroanalytical method is described for the analysis of propanil in commercial products that contain propanil as the active ingredient, used in the treatment of rice crops in Portugal.
- Revealing the immunomodulatory potential of pyrazoles and exploring structure-activity relationshipsPublication . Silva, Jorge Miguel Almeida; Rocha, S.; Silva, V. L. M.; Silva, A. M. S.; Moreira, Fernando; Fernandes, E.; Freitas, M.Inflammation is a complex and tightly regulated process by a cascade of events that involves the production of prostaglandins (PG) by the inducible isoform cyclooxygenase 2 (COX-2) and the production of reactive pro-oxidant species. Conversely, COX-1, which is consistently present in a variety of tissues, has traditionally been categorized as the primary isoform responsible for maintaining the balance of prostaglandin production. Given the adverse effects associated with currently employed antiinflammatory agents, there is an urgent need to develop novel and efficacious compounds capable of regulating the inflammatory cascade. In this sense, a panel of 28 structurally related pyrazoles were evaluated through the inhibition of human COX-2 and ovine COX-1 activity; the ex vivo production of PGE2 in human whole blood; COX-2 expression in human leukocytes; and human leukocytes’ oxidative burst. The results revealed that some of the tested pyrazoles had a significant inhibitory effect on COX- 2 activity. Pyrazoles 4 and 11B (Fig. 1) stood out as the most potent inhibitors. Pyrazole 11B exhibited greater inhibitory activity against COX-2 than COX-1, while pyrazole 14 displayed selective inhibition of COX-1, with an IC50 value lower than 1 μM. Interestingly, pyrazoles 14 and 16 (Fig. 1) downregulated the COX-2 expression in human leukocytes. Several of the tested pyrazoles, namely compound 4, showed a potential suppressive effect (IC50 5 μM) against human leukocytes’ oxidative burst. In addition, various pyrazoles were able to inhibit both COX-2 activity and oxidative burst, particularly the pyrazoles 1B, 4 and 11B.