Bipyridylium quaternary salts and related compounds. Part IV. Pyridones derived from paraquat and diquat

Calderbank, A.; Charlton, D. F.; Farrington, John A.; James, R Pankhurst

doi:10.1039/p19720000138

Cited by 29 publications

(22 citation statements)

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“…The paraquat peak is still visible after 3 h, accompanied by a hump for l >270 nm, already noticeable for the spectrum recorded after 1.5 h. An increase of absorbance occurs between 220 and 240 nm for the spectra acquired at t = 1.5 h followed by a decrease, probably due to formation of intermediate species, which is in accordance with other authors [28,32]. The comparison of the bands for the paraquat electrolyzed solutions and those for possible by-products such as paraquat monopyridone: 225, 257, and 345 nm [33] or 222, 260, 347 nm [34], and paraquat dipyridone: 224 and 320 nm [33], indicates that these compounds are the main by-products of paraquat in neutral medium. This assumption is in accordance with published data [18,21,28,32].…”

Section: Uv-vis Absorption Spectroscopysupporting

confidence: 75%

Electrochemical oxidation of paraquat in neutral medium

Cartaxo

Borges

Pereira

et al. 2015

Electrochimica Acta

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Section: Uv-vis Absorption Spectroscopysupporting

confidence: 75%

Electrochemical oxidation of paraquat in neutral medium

Cartaxo

Borges

Pereira

et al. 2015

Electrochimica Acta

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“…Identification of the APMV peptides was carried out by treatment of aliquots of the lyophilized fractions eluted from the HPLC column with 2 M NAOH for 5 hours. Where APMV was present, a blue fluorescent pyridone was observed (Calderbank et al, 1972).…”

Section: Photochemical Reduction Of Chemically Modified Fnr (Fnr-apmv)mentioning

confidence: 99%

“…The method followed included the proteolytic digestion of the modified enzyme and separation of the peptides by HPLC for further sequencing. Several methods failed to identify the viologen bound to the corresponding amino acid until it was found in the literature that treatment of viologens with 2 M NAOH produced a strong fluorescent derivative with blue fluorescence (Calderbank et al, 1972) each time. Both procedures gave a different peptide, but lead to similar results, indicating that the fluorescent label was present in a peptide with the following sequence: Glu-Met-Leu-LeuPro-Asp-Asp-Pro-Glu-Ala.…”

Section: Potential (V)mentioning

confidence: 99%

The Covalent Linkage of a Viologen to a Flavoprotein Reductase Transforms it into an Oxidase

Bes

Lacey

Peleato

et al. 1995

European Journal of Biochemistry

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Chemical cross-linkage of the positively charged viologen N-methyl-K-(aminopropyl)-4-4'-bipyridinium dibromide (APMV) to the enzyme ferredoxin-NADP' reductase from the cyanobacterium Anabaenu PCC 71 19 has been performed using the carbodiimide 1 -ethyl[3-(3-dimethylaminopropyl)]carbodiimide. 0.5-1 mol, depending on the preparation, is introduced for each mol enzyme. The residue involved in the covalent linkage with the viologen, Glu139, has been identified using HPLC separation of the modified proteolytic peptides and subsequent sequencing. Modification of the enzyme changes its catalytic specificity since it is able to react directly with oxygen; this is observed by a high NADPH oxidase activity, which is completely absent in the native enzyme. More important, this new enzymic activity is indicative of the intramolecular electron transfer between the natural redox cofactor FAD and the artificially introduced viologen. Electrons can also flow in the reverse direction, from the viologen to the FAD group, then to NADP', when the reaction is performed using glassy-carbon electrodes to reduce the viologen. Cyclic voltammetry experiments have shown that there is a small catalytic current between the electrode and the enzyme which is not observed in the native enzyme.

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“…The metabolic turnover rate of DQ is higher than that of PQ in liver homogenates [10]. The present yellow derivative does not correspond to either of the two metabolites reported previously [11], because the absorption peak of both metabolites is 357 nm and both metabolites are quite soluble in chloroform, whereas this derivative absorbs light at 420 nm and is insoluble in chloroform. DQ is photodegraded more easily than PQ [12,13] but the present yellow derivative is none of the photodegraded products reported previously [13] because they only absorb light at wavelengths shorter than 270 nm [12].…”

Section: Resultsmentioning

confidence: 54%

“…Previously we reported a red DQ derivative which was produced by moderate reduction in alkaline pH [8]. The present yellow derivative has a higher molar absorptivity (ε 420 = 27 600) than DQ itself (ε 310 = 19 200) [6], its radical (ε 430 = 4140) [6], its metabolites (ε 357 = 14 900) [11] and its red derivative (ε 495 = 20 700) [8] reported before. We are now investigating the structure of the derivative.…”

Section: Resultsmentioning

confidence: 86%

A new diquat derivative appropriate for colourimetric measurements of biological materials in the presence of paraquat

Minakata¹,

Сузукі²,

Saito³

et al. 2000

International Journal of Legal Medicine

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A new colourimetric method is described for the quantification of diquat using a yellow-coloured derivative produced by heating diquat in alkaline solution at 80 degrees C. The absorption maximum of the yellow derivative is 420 nm and the molar absorption coefficient is 2.76 x 10(4) (0.15 in 1 microgram diquat/ml with 1 cm light path). The absorption at 420 nm shows a linear concentration dependence in the range 0.1-10 micrograms/ml and fading of the colour is about 5% after 1 h. Under the same conditions, paraquat does not produce any coloured products. The concentration of diquat in the solution containing both diquat and paraquat can be determined by the absorption of diquat derivative at 420 nm without interference from paraquat. By adding sodium dithionite to the solution the concentration of paraquat can be determined by the absorption of paraquat radicals at 600 nm without interference from diquat, because the yellow derivative does not react with dithionite. This yellow diquat derivative can be extracted completely with cyclohexanol by saturating the solution with Na2SO4. The absorption maximum in cyclohexanol shifts to 440 nm with the same molar absorbance and the same half-band width as in water. Fading of the colour is less than 5% after 24 h in cyclohexanol. Perchloric acid (3%) and trichloroacetic acid (4.5%) which are often used for deproteinization of tissue homogenates, do not inhibit production of the coloured derivative at pH 13.5 or extraction of the derivative with cyclohexanol. This method is suitable for a quick determination of small amounts of diquat in tissues, since the extraction with cyclohexanol not only concentrates the derivative rapidly but also quite efficiently eliminates the coloured substances in tissue homogenates. The detection limit of diquat is 0.02 microgram/ml for blood and 0.05 microgram/g for liver when 1 ml or 1 g is used for analysis. In three human cases of fatal intoxication, both paraquat and diquat were quantified using 50 microliters of serum. In non-toxic dosing of diquat to rats for 14 days, the diquat level was highest in the spleen followed by the kidneys.

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Bipyridylium quaternary salts and related compounds. Part IV. Pyridones derived from paraquat and diquat

Cited by 29 publications

References 0 publications

Electrochemical oxidation of paraquat in neutral medium

Electrochemical oxidation of paraquat in neutral medium

The Covalent Linkage of a Viologen to a Flavoprotein Reductase Transforms it into an Oxidase

A new diquat derivative appropriate for colourimetric measurements of biological materials in the presence of paraquat

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