Antioxidant Paradoxes of Phenolic Compounds: Peroxyl Radical Scavenger and Lipid Antioxidant, Etoposide (VP-16), Inhibits Sarcoplasmic Reticulum Ca2+-ATPase via Thiol Oxidation by Its Phenoxyl Radical

Hydroxycinnamic acids (such as ferulic, caffeic, sinapic, andp-coumaric acids) are a group of compounds highly abundant in food that may account for about one-third of the phenolic compounds in our diet. Hydroxycinnamic acids have gained an increasing interest in health because they are known to be potent antioxidants. These compounds have been described as chain-breaking antioxidants acting through radical scavenging activity, that is related to their hydrogen or electron donating capacity and to the ability to delocalize/stabilize the resulting phenoxyl radical within their structure. The free radical scavenger ability of antioxidants can be predicted from standard one-electron potentials. Thus, voltammetric methods have often been applied to characterize a diversity of natural and synthetic antioxidants essentially to get an insight into their mechanism and also as an important tool for the rational design of new and potent antioxidants. The structure-property-activity relationships (SPARs) correlations already established for this type of compounds suggest that redox potentials could be considered a good measure of antioxidant activity and an accurate guideline on the drug discovery and development process. Due to its magnitude in the antioxidant field, the electrochemistry of hydroxycinnamic acid-based antioxidants is reviewed highlighting the structure-property-activity relationships (SPARs) obtained so far.

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Oxidative damage to sarcoplasmic reticulum Ca2+-pump induced by Fe2+/H2O2/ascorbate is not mediated by lipid peroxidation or thiol oxidation and leads to protein fragmentation

Molecular and Cellular Biochemistry ◽

10.1007/bf00420912 ◽

1996 ◽

Vol 159 (2) ◽

pp. 105-114 ◽

Cited By ~ 46

Author(s):

Roger F. Castilho ◽

Paulo C. Carvalho-Alves ◽

Anibal E. Vercesi ◽

S�rgio T. Ferreira

Keyword(s):

Lipid Peroxidation ◽

Sarcoplasmic Reticulum ◽

Oxidative Damage ◽

Thiol Oxidation ◽

Protein Fragmentation

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Stimulation of the cyanide-resistant alternative respiratory pathway by oxygen in Acremonium chrysogenum correlates with the size of the intracellular peroxide pool

Canadian Journal of Microbiology ◽

10.1139/w03-029 ◽

2003 ◽

Vol 49 (3) ◽

pp. 216-220 ◽

Cited By ~ 2

Author(s):

Levente Karaffa ◽

Erzsébet Sándor ◽

Erzsébet Fekete ◽

József Kozma ◽

Attila Szentirmai ◽

...

Keyword(s):

Glucose Uptake ◽

Respiratory Activity ◽

Peroxyl Radical ◽

Radical Scavenger ◽

Acremonium Chrysogenum ◽

Alternative Respiration ◽

Respiratory Pathway ◽

Submerged Cultures ◽

Alternative Respiratory Pathway ◽

The Relationship

The relationship between oxygen input and activity of the cyanide-resistant alternative respiration of submerged cultures of Acremonium crysogenum was investigated. The volumetric oxygen transfer coefficient of the respective cultures correlated positively within almost two ranges of magnitude with the size of the intracellular peroxide pool, which in turn, correlated with the activity of the cyanide-resistant alternative respiratory pathway. Increased aeration also stimulated the glucose uptake rate but had no effect on the total respiration rate or the growth rate. Addition of the lipid peroxyl radical scavenger DL-α-tocopherol to A. chrysogenum cultures decreased the rate of intracellular peroxide production as well as glucose uptake. An increase in the cyanide-resistant fraction of total respiration was observed, while growth and the total respiratory activity remained unchanged. We conclude that intracellular peroxides may stimulate the alternative respiration in A. chrysogenum.Key words: Acremonium chrysogenum, alternative respiration, oxygen, peroxide, Kla.

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