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.

scholarly journals Antioxidant properties, quantification and stability of betalains from pitaya (Hylocereus undatus) peel

2014 ◽  
Vol 45 (2) ◽  
pp. 323-328 ◽  
Author(s):  
Fernanda Robert de Mello ◽  
Claudia Bernardo ◽  
Caroline Odebrecht Dias ◽  
Luciano Gonzaga ◽  
Edna Regina Amante ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Phenolic Compounds ◽  
Antioxidant Properties ◽  
Raw Material ◽  
High Concentration ◽  
Natural Colorant ◽  
Wide Ph Range ◽  
Hylocereus Undatus ◽  
Ph Range ◽  
Promising Source

Pitaya peel can be used as a raw material for betalains extraction. The aim of this research was to quantify phenolic compounds, antioxidant activity and betalains on pitaya peel. Furthermore, evaluate the betalains stability against various pH conditions and exposure time of heating. The results showed that pitaya peel contains phenolic compounds and presented antioxidant activity. Moreover it showed high concentration of betalains (101.04mg equivalent to betanin. 100g-1) which were stable over a wide pH range (3.2 - 7.0) and were resistant to heating (100oC) up to 10 minutes at pH range from 3.7 to 5.5. Therefore, pitaya peel is a promising source of betalains which can be applied as a natural colorant for food.

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.

scholarly journals Melatonin as a Reducer of Neuro- and Vasculotoxic Oxidative Stress Induced by Homocysteine

Antioxidants ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1178
Author(s):  
Kamil Karolczak ◽  
Cezary Watala
Keyword(s):  
Oxidative Stress ◽  
Structural Changes ◽  
Clinical Evidence ◽  
Neuronal Degeneration ◽  
Antioxidant Properties ◽  
In Vitro Models ◽  
In Vivo Models ◽  
Initial Research

The antioxidant properties of melatonin can be successfully used to reduce the effects of oxidative stress caused by homocysteine. The beneficial actions of melatonin are mainly due to its ability to inhibit the generation of the hydroxyl radical during the oxidation of homocysteine. Melatonin protects endothelial cells, neurons, and glia against the action of oxygen radicals generated by homocysteine and prevents the structural changes in cells that lead to impaired contractility of blood vessels and neuronal degeneration. It can be, therefore, assumed that the results obtained in experiments performed mainly in the in vitro models and occasionally in animal models may clear the way to clinical applications of melatonin in patients with hyperhomocysteinemia, who exhibit a higher risk of developing neurodegenerative diseases (e.g., Parkinson’s disease or Alzheimer’s disease) and cardiovascular diseases of atherothrombotic etiology. However, the results that have been obtained so far are scarce and have seldom been performed on advanced in vivo models. All findings predominately originate from the use of in vitro models and the scarcity of clinical evidence is huge. Thus, this mini-review should be considered as a summary of the outcomes of the initial research in the field concerning the use of melatonin as a possibly efficient attenuator of oxidative stress induced by homocysteine.

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.

Molecular geometry of (E)- and (Z)-9-(β-Styryl)anthracenes

1984 ◽  
Vol 37 (11) ◽  
pp. 2215 ◽  
Author(s):  
H Becker ◽  
VA Patrick ◽  
AH White
Keyword(s):  
Fine Structure ◽  
Double Bond ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Molecular Geometry ◽  
Diels Alder ◽  
Molecular Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Limited Mobility

The molecular structures of (Z)-9-(8-styryl)anthracene, C22H16,(I),(E)-9-(P-styryl)anthracene, (2), and the photo-Diels-Alder dimer of 9-phenylethynylanthracene, C44H28, (3), containing a (Z)-9- (β-styryl) anthracene moiety of limited mobility have been determined by X-ray diffraction. Crystals of (1) are monoclinic, P21/c, a 5.507(4), b 13.050(7), c 21.425(10)�, β 95.73(5)�, Z 4; R was 0.047 for No 1604 independent 'observed' reflections. Crystals of (2) are monoclinic, P21/n, a 11.77(1), b 24.35(2), c 5.503(5) �, β 107.38(7)�, Z 4; R 0.050 for No 1100. Crystals of (3) are monoclinic, P21/c, a 10.719(7), b 18.627(8), c 15.509(8) �, β 101.10(5)�, Z 4; R 0.070 for No 1055. Increase in angle between the plane of the anthracene and the plane of the ethylenic double bond (78.4, 65.5, 81.9� respectively) is reflected in the electronic absorption spectra by an enhancement of the fine structure typical of the anthracene chromophore.

scholarly journals In Vitro Evaluation of Pro- and Antioxidant Effects of Flavonoid Tricetin in Comparison to Myricetin

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5850
Author(s):  
Vladimir Chobot ◽  
Franz Hadacek ◽  
Gert Bachmann ◽  
Wolfram Weckwerth ◽  
Lenka Kubicova
Keyword(s):  
Structural Changes ◽  
Antioxidant Properties ◽  
Differential Pulse ◽  
Mesomeric Effect ◽  
Physiological Processes ◽  
Phenolic Constituents ◽  
Deoxyribose Degradation ◽  
Signal Cascades ◽  
Antioxidant Effects

Flavonoids are rather common plant phenolic constituents that are known for potent antioxidant effects and can be beneficial for human health. Flavonoids with a pyrogallol moiety are highly efficient reducing agents with possible pro- and antioxidant effects, depending on the reaction milieu. Therefore, the redox properties of myricetin and tricetin were investigated by differential pulse voltammetry and deoxyribose degradation assay. Tricetin proved to be a good antioxidant but only showed negligible pro-oxidant activity in one of the deoxyribose degradation assay variants. Compared to tricetin, myricetin showed pro- and antioxidant effects. The more efficient reducing properties of myricetin are probably caused by the positive mesomeric effect of the enolic 3-hydroxy group on ring C. It is evident that the antioxidant properties of structurally similar flavonoids can be converted to apparent pro-oxidant effects by relatively small structural changes, such as hydroxylation. Since reactive oxygen species (ROS) often serve as secondary messengers in pathological and physiological processes in animal and plant cells, the pro- and antioxidant properties of flavonoids are an important part of controlling mechanisms of tissue signal cascades.

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