Structural changes of flavylium salts. II. Polargographic and spectrometric investigation of 4'-Hydroxyflavylium perchlorate

1967 ◽  
Vol 20 (4) ◽  
pp. 745 ◽  
Author(s):  
KA Harper ◽  
BV Chandler
Keyword(s):  
Structural Changes ◽  
Polarographic Reduction ◽  
Spectrometric Investigation ◽  
High Ph ◽  
Low Concentration ◽  
Methanolic Solution ◽  
Electrode Reactions ◽  
Wide Ph Range ◽  
Ph Range

4?-Hydroxyflavylium perchlorate is examined polarographically and spectrometrically in aqueous methanolic solution over a wide pH range. In solutions below pH 3 the flavonoid moiety exists solely as the flavylium ion, which establishes an equilibrium with the pseudobase, the anhydrobase, and the 2-hydroxychalcone above this pH. The flavylium ion disappears from solution above pH 5, the anhydrobase remains at a constant low concentration, and the ratio of pseudobase to chalcone fluctuates as the pH is increased. Electrode reactions for the various reductions are the same as those previously described for 7,4?- dihydroxyflavylium perchlorate. Without influencing the polarographic reduction, the presence of mercury in the polarographic cell favours chalcone formation in neutral solutions and suppresses resonance in the chalcone ion at high pH, probably through formation of a mercuric chelate.

Structural changes of flavylium salts. IV. Polarographic and spectrometric examination of pelargonidin chloride

1968 ◽  
Vol 21 (1) ◽  
pp. 221 ◽  
Author(s):  
KA Harper
Keyword(s):  
Ring Opening ◽  
Structural Changes ◽  
Equilibrium Mixture ◽  
Ring Cleavage ◽  
Alkaline Solutions ◽  
Similar Reaction ◽  
Anodic Wave ◽  
Wide Ph Range ◽  
Phenolic Group ◽  
Ph Range

Pelargonidin chloride has been examined polarographically and spectrometrically in aqueous methanol over a wide pH range and the molecular changes determined. In strongly acid solutions the flavylium ion is stable, but between pH3 and pH8 ring opening to the α-diketone occurs, the process involving the pseudo-base and its 3-keto tautomer. The pseudo-base is present in the equilibrium mixture from pH3 to pH12 in amount varying with the pH. The anhydrobase, detected in the equilibrium mixture at pH6, is stable above pH7, becoming ionized as the pH is raised. Unlike the anhydrobase of the simpler flavylium salts, the anhydrobase of pelargonidin chloride does not undergo ring cleavage in strong alkali under the conditions of these experiments. Ionization of the phenolic group at C5 was indicated by a, small anodic wave in the polarograms above pH9.5, due to mercuration at C6. A similar reaction, analogous to the known catalytic mercuration of ketones, was observed for phloroglucinol and resorcinol in alkaline solutions.

Morphogenesis-Associated/Dissociated Production of Epothilone in Wild Sorangium Cellulosum Strains

2011 ◽  
Vol 343-344 ◽  
pp. 951-957
Author(s):  
Xin Li Liu ◽  
Lin Zhao ◽  
Wei Hu ◽  
Yue Zhong Li
Keyword(s):  
Fruiting Body ◽  
Fruiting Bodies ◽  
Sorangium Cellulosum ◽  
Strongly Coupled ◽  
High Ph ◽  
Ph Values ◽  
Wide Ph Range ◽  
Ph Range

To investigate the characters ofSorangiumstrains and the approaches for improving the production of epothilone, correlation of epothilone production and morphogenesis was studied in strains So0157-2, So0007-3andSo0003-3. On lean medium, So0157-2 could produce epothilones in a wide pH range (5.0-12.0), but formed fruiting bodies at high pH values (9.0-14.0). Formation of fruiting body did not affect the yield of epothilones in So0157-2. In So0007-3 and So0003-3, producing of epothilone was strongly coupled with the process of morphogenesis. It suggests that reduction of the association between morphogenesis and epothilone producing would prominently improve the epothilone production.

scholarly journals The spectroabsorptiometric and voltammetric behavior of malvin in buffered solutions and its antioxidant properties

2002 ◽  
Vol 67 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Ljubisa Ignjatovic ◽  
Jasmina Dimitric-Markovic ◽  
Dragan Markovic ◽  
Jelisaveta Baranac
Keyword(s):  
Electronic Absorption ◽  
Structural Changes ◽  
Electronic Absorption Spectra ◽  
Antioxidant Properties ◽  
Oxidation Potential ◽  
Molecular Structures ◽  
Wide Ph Range ◽  
Voltammetric Behavior ◽  
Ph Range

In the present work the structural transformations of malvin in aqueous acetate buffer solutions were investigated over a wide pH range under in vitro conditions using electronic absorption spectroscopy. In addition to the spectroabsorptiometric investigation, the voltammetric behavior and the mechanism of the redox process of this molecule were studied, in order to define its antioxidant properties. The electronic absorption spectra reveal that the structural changes of malvin, caused by changes in the pH of the medium, lead to changes in the voltammetric behaviour of this molecule. The dependence of the oxidation potential of malvin on pH, which can be explained by the presence of different electroactive molecular structures of malvin at different pH values, indicates different mechanisms of the electrode process. The voltammetric activity of malvin is compared semiquantitatively with the voltammetric activity of a standard synthetic antioxidant, BHA, and a natural antioxidant, quercetin.

Transport methods as complementary tools for speciation purposes

2005 ◽  
Vol 93 (11) ◽  
Author(s):  
B. Fourest ◽  
V. Sladkov
Keyword(s):  
Capillary Electrophoresis ◽  
Radioactive Waste ◽  
Waste Management ◽  
Present Article ◽  
Fission Products ◽  
Radioactive Waste Management ◽  
Low Concentration ◽  
Capillary Method ◽  
Wide Ph Range ◽  
Ph Range

SummaryTransport methods, and especially capillary electrophoresis, are shown to bring with a high simplicity and efficiency useful complementary data to solve some speciation problems. Their application in this aim is particularly interesting in the case of actinides or solutions resulting from the radioactive waste management. In the present article, three examples are proposed to illustrate this point. In the first one, the open-end capillary method is applied to point out the hydrolyzed species of Pa(V) over a wide pH range. The difficulties overcome in this case are related to the very low concentration and specific properties of the element under consideration. The second illustration concerns the complexation of uranyl by the anionic forms of some long-lived fission products (MO

Polarographic and spectrophotometric behaviour of some N-p-phenyl substituted benzamidines

1991 ◽  
Vol 56 (12) ◽  
pp. 2791-2799 ◽  
Author(s):  
Juan A. Squella ◽  
Luis J. Nuñez-Vergara ◽  
Hernan Rodríguez ◽  
Amelia Márquez ◽  
Jose M. Rodríguez-Mellado ◽  
...  
Keyword(s):  
Spectrophotometric Study ◽  
Absorption Bands ◽  
Electrochemical Parameters ◽  
Wide Ph Range ◽  
Group A ◽  
Substituent Constants ◽  
Ph Range ◽  
The Waves

Five N-p-phenyl substituted benzamidines were studied by DC and DP polarography in a wide pH range. Coulometric results show that the overall processes are four-electron reductions. Logarithmic analysis of the waves indicate that the process are irreversible. The influence of the pH on the polarographic parameters was also studied. A UV spectrophotometric study was performed in the pH range 2-13. In basic media some variations in the absorption bands were observed due to the dissociation of the amidine group. A determination of the pK values was made by deconvolution of the spectra. Correlations of both the electrochemical parameters and spectrophotometric pK values with the Hammett substituent constants were obtained.

High degradation efficiency of sulfamethazine with the dual-reaction-center Fe-Mn-SiO2 Fenton-like nanocatalyst in a wide pH range

2021 ◽  
Author(s):  
Manoj Kumar Panjwani ◽  
Qing Wang ◽  
Yueming Ma ◽  
Yuxuan Lin ◽  
Feng Xiao ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Reaction Center ◽  
Degradation Efficiency ◽  
Heterogeneous Fenton ◽  
Wide Ph Range ◽  
Ph Range

The development of a heterogeneous Fenton-like catalyst, possessing high degradation efficiency in a wide pH range, is crucial for wastewater treatment. The Fe-Mn-SiO2 catalyst was designed, and prepared by a...

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