Calculated antioxidant activity of selected phenolic compounds

Determination of the corresponding bond dissociation enthalpy, ionization potential and proton affinity, dipole moment values, highest occupied molecular orbital eigenvalues, and spin density along with the bioactivity score is central to the antioxidant activity evaluation in this paper. Molecular geometries were optimized with DFT using B3LYP and UB3LYP for parent, ionic, and radical species and 6-311+G(d,p) basis set. Bioactivity, drug likeness, and drug scores were calculated using freely available cheminformatics programs for data visualization and analysis. Overall, the values revealed two structures as promising molecules because of good reaction enthalpies (ΔHr). Lipinski rules were fully satisfied for all molecules.

THEORETICAL STUDY OF THE SUBSTITUENT EFFECTS ON THE REACTION ENTHALPIES OF THE ANTIOXIDANT MECHANISMS OF STOBADINE DERIVATIVES IN THE GAS-PHASE AND WATER

In this paper the reaction enthalpies of three antioxidant action mechanisms, HAT, SET–PT, and SPLET, for mono-substituted Stobadines were calculated in gas-phase and water. Results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP), and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In comparison to gas-phase, water attenuates the substituent effect on all reaction enthalpies. Results show that IP and BDE values can be successfully correlated with the indolic N–H bond length after electron abstraction, R(N–H+•), and the partial charge on the indolyl radical nitrogen atom, q( N ). Furthermore, calculated IP and PA values for mono-substituted Stobadines show linear dependence on the energy of the highest occupied molecular orbital (E HOMO ) of studied molecules in the two environments. SPLET represents the thermodynamically preferred mechanism in water.

Melatonin as a natural ally against oxidative stress: a physicochemical examination

Oxidative stress has been proven to be related to the onset of a large number of health disorders. This chemical stress is triggered by an excess of free radicals, which are generated in cells because of a wide variety of exogenous and endogenous processes. Therefore, finding strategies for efficiently detoxifying free radicals has become a subject of a great interest, from both an academic and practical points of view. Melatonin is a ubiquitous and versatile molecule that exhibits most of the desirable characteristics of a good antioxidant. The amount of data gathered so far regarding the protective action of melatonin against oxidative stress is overwhelming. However, rather little is known concerning the chemical mechanisms involved in this activity. This review summarizes the current progress in understanding the physicochemical insights related to the free radical-scavenging activity of melatonin. Thus far, there is a general agreement that electron transfer and hydrogen transfer are the main mechanisms involved in the reactions of melatonin with free radicals. However, the relative importance of other mechanisms is also analyzed. The chemical nature of the reacting free radical also has an influence on the relative importance of the different mechanisms of these reactions. Therefore, this point has also been discussed in detail in the current review. Based on the available data, it is concluded that melatonin efficiently protects against oxidative stress by a variety of mechanisms. Moreover, it is proposed that even though it has been referred to as the chemical expression of darkness, perhaps it could also be referred to as the chemical light of health.

Ferulenol specifically inhibits succinate ubiquinone reductase at the level of the ubiquinone cycle

The natural compound ferulenol, a sesquiterpene prenylated coumarin derivative, was purified from Ferula vesceritensis and its mitochondrial effects were studied. Ferulenol caused inhibition of oxidative phoshorylation. At low concentrations, ferulenol inhibited ATP synthesis by inhibition of the adenine nucleotide translocase without limitation of mitochondrial respiration. At higher concentrations, ferulenol inhibited oxygen consumption. Ferulenol caused specific inhibition of succinate ubiquinone reductase without altering succinate dehydrogenase activity of the complex II. This inhibition results from a limitation of electron transfers initiated by the reduction of ubiquinone to ubiquinol in the ubiquinone cycle. This original mechanism of action makes ferulenol a useful tool to study the physiological role and the mechanism of electron transfer in the complex II. In addition, these data provide an additional mechanism by which ferulenol may alter cell function and demonstrate that mitochondrial dysfunction is an important determinant in Ferula plant toxicity.

Calculation of the relative acidities and oxidation potentials of para-substituted phenols. A model for α-tocopherol in solution

Relative acidities (Delta pK(a)) of phenols and oxidation potentials (Delta E(ox)) of the phenoxide anions have been calculated for nine para-substituted phenols using density functional theory. Solvent effects were incorporated using the conductor-like polarisable continuum method. Using the calculated Delta pK(a) and Delta E(ox) values in a thermodynamic cycle, the DeltaBDE (bond dissociation enthalpy) of the phenols were also determined with all values calculated to within 1.5 kcal mol(-1) of experiment. The Delta pK(a) and Delta E(ox) values were calculated for 6-hydroxy-2,2,5,7,8-pentamethylchroman (HPMC), a model for alpha-tocopherol for which there are no known experimental values. The acidity of this compound is raised by 2.4 pK(a) units and lowered by -0.79 V relative to phenol with a calculated Delta BDE of -14.9 kcal mol(-1). There is a negative correlation (r(2) = 0.86) between the Delta pK(a) and the Delta BDE values. A stronger and positive correlation is found between the Delta E(ox) (r(2) = 0.98) and the Delta BDE values. Using these correlations it is uncovered that hydrogen abstraction of phenols, as measured by the Delta BDE, is driven by electron transfer rather than by proton transfer.

Perturbing effects of carvedilol on a model membrane system: Role of lipophilicity and chemical structure

Carvedilol, a beta-adrenergic blocker used to treat cardiovascular diseases, protects cell membranes from lipid peroxidative damage. Previous studies suggested the drug resides in a non-polar environment and partitions into cell membranes, perturbing their fluidity. Here differential scanning calorimetry (DSC) and fluorescence spectroscopy were applied to further investigate interactions of carvedilol with a liposome model. Results indicate the association is relatively unaffected by pH or temperature, but could be sensitive to liposome composition. The drug's carbazole group plays the dominant role in bilayer perturbation. Compared with other beta-blockers examined, carvedilol produced the strongest liposome DSC perturbation. Locations of carbazole and carvedilol in the liposome were determined using depth-dependent fluorescent probes. Both compounds are situated in the middle of the bilayer, consistent with strong hydrophobic interactions. This combination of high lipophilicity and specific chemical structure appear required for carvedilol's novel antioxidant activity, and may enhance cardioprotection.

Imidazolopyrazinones as potential antioxidants

A series of imidazolopyrazinones 3, substituted at C-2, and C-2/C-6, has been prepared. The compounds behaved as quenchers of superoxide anion. The more active compounds are structurally related to coelenterazine, a natural substrate of marine bioluminescence. Theoretical parameters based on Hartree-Fock instabilities have been examined.

Clinical Pharmacology of Carvedilol

BACKGROUND: There is now a wealth of data supporting the use of beta-blockers in heart failure and the additional pharmacological properties of carvedilol are thought to play an important role in the therapeutic efficacy of carvedilol in this disease. METHODS AND RESULTS: Carvedilol is licensed for the treatment of essential hypertension, chronic stable angina, and mild to moderate chronic heart failure. This article provides an up-to-date review of the clinical pharmacology of carvedilol, with particular emphasis on its clinical effects in heart failure. CONCLUSION: Carvedilol is a multiple-action neurohormonal antagonist that offers nonselective beta-blockade, alpha-1 blockade, antioxidant, anti-ischemic mortality, and anti-proliferative properties. In addition to reductions in hospitalization and mortality rates, benefits of carvedilol in heart failure include dramatic improvements in left ventricular function and other parameters of cardiac remodeling.

Structure-activity relationships in a series of melatonin analogues with the low-density lipoprotein oxidation model

Despite an increasing number of publications concerning the antioxidant activity of melatonin, little is known about the structural features responsible for this kind of activity. To understand the role played by the different elements of melatonin structure in its antioxidant activity, we have designed and tested several compounds related to this molecule in the low-density lipoprotein peroxidation model. We present here the results of this study in terms of structure-activity relationships focusing on the influence of the acetamidoethyl side chain, the methoxy group, and the indole heterocycle. In this model, we found that changing the acyl residue generally resulted in more active products. We obtained particularly good results with the nonanoyl derivative which showed a level of activity comparable to that of phenols despite lacking a phenolic function. The presence of a methoxy group in position 5 generally had a beneficial influence on the activity, but when located in position 6, the effects were various. The substitution of a hydroxy for the methoxy group led to phenolic compounds endowed with very high antioxidant activity. Replacing the amide with a ketone function did not affect the activity while replacement with an amine group in some cases resulted in prooxidant compounds. Finally, we compared the efficacy of different aromatic rings. The indole heterocycle proved to be better than benzofurane and naphthalene rings.