Hydroxyl radical scavenging action of capsaicin

Method for assessing X-ray-induced hydroxyl radical-scavenging activity of biological compounds/materials

A method for correctly assessing hydroxyl radical scavenging activity of antioxidative chemicals and/or biological compounds/materials was proposed. This method can simultaneously assess two factors, i.e. hydroxyl radical-scavenging and 5,5-dimethyl-2-hydroxy-1-pyrrolidine-N-oxide (hydroxyl radical adduct of 5,5-dimethyl-1-pyrroline-N-oxide)-reducing ability, as antioxidative properties. In this paper, some biologically common hydrophilic molecules, cell culture media, and rat plasma were tested. X-ray-induced hydroxyl radical can be detected using the electron paramagnetic resonance spin trapping technique. Using X-ray irradiation of the reaction mixture as the hydroxyl radical source, the true hydroxyl radical-scavenging ability of the subjected antioxidant can be assessed. In addition, the method simultaneously measures the reduction of 5,5-dimethyl-2-hydroxy-1-pyrrolidine-N-oxide, to estimate the reducing ability of the antioxidant. Biological materials, such as sugars and proteins, could abolish hydroxyl radical at the biological concentration. Ascorbic acid showed reducing ability at the biological concentration. The simultaneous assessment of hydroxyl radical-scavenging and reducing ability of antioxidants can be an informative index for antioxidants.

Quercetin and naringenin reduce abnormal development of mouse embryos produced by hydroxyurea

OBJECTIVES

There is limited evidence about the impact of quercetin and naringenin on embryonic development. The purpose of this work was to evaluate in vitro their direct teratogenic potential as well as their protective activity against teratogenesis mediated by oxidative damage on mouse embryos.

METHODS

Quercetin and naringenin toxicity on whole mouse cultured embryos, as well as their ability to protect embryos against hydroxyurea-induced insult were evaluated.

KEY FINDINGS

Quercetin 100 microm and naringenin 300 microm produced significant reduction of developmental and growth parameters, in comparison with those of the control group. Embryos exposed to the concurrent administration of quercetin or naringenin with hydroxyurea (2 microm, 2 h) were significantly protected from growth and developmental retardation, and abnormalities induced by hydroxyurea. Interestingly, embryos exposed to hydroxyurea and dimethyl sulfoxide 0.1%, the vehicle employed to dissolve flavonoids, also showed significant damage amelioration.

CONCLUSIONS

These results indicate that quercetin and naringenin have not only a minor toxic effect on development, but also a protective effect against hydroxyurea-induced embryonic damage.

Antioxidant activity of thiosulfinates derived from garlic

Garlic extract significantly inhibited the oxidation of methyl linoleate in homogeneous acetonitrile solution, whereas the antioxidant effect of allicin-free garlic extract, prepared by removing allicin by prepared by removing allicin by preparative HPLC, was much lower than that of the garlic extract. These results suggest that the antioxidant properties are mostly attributed to the presence of allicin in the garlic extract. Allicin a major component of the thiosulfinates in garlic extract, was found to be effective for inhibiting methyl linoleate oxidation, but its efficiency was less than that of alpha-tocopherol. Next, the reactivity of allicin toward the peroxyl radical, which is a chain-propagating species, was investigated by direct ESR detection. The addition allicin to 2,2'-azobis(2,4-dimethylvaleronitrile)-peroxyl radical solution caused the signal intensity of the peroxyl radical to dose-dependently decrease, indicating that allicin is capable of scavenging the the peroxyl radical and acting as an antioxidant. Finally, we studied the structure-anioxidant activity relationship for thiosulfinates and suggested that the combination of the allyl group (-CH2CH=CH2) and the -S(O)S- group is necessary for the antioxidant action of thiosulfinates in the garlic extract. In addition, one of the two possible combinations, -S(O)S-CH2CH=CH2, was found to make a much larger contribution to the antioxidant activity of the thiosulfinates than the other, CH2=CH-CH2-S(O)S-.

Oxidative stress and electron spin resonance

The body constantly reacts with oxygen as part of the energy producing processes of cells. Oxidative stress is a dysbalance between the production of free radicals as products of these reactions and antioxidant properties of cells. The factors influencing the production of free radicals are physical agents, chemical agents and biological agents. Free radicals are paramagnetic molecules with short time-period for their detection by electron spin resonance (ESR) spectroscopy. The free radical stabilization can be gained by freezing a solution of an organic radical or bonding to spin trapping agents. The spin trapping agents are diamagnetic compounds which rapidly scavenge transient radicals to form stable paramagnetic spin adducts radicals. Because this secondary radical retains an unpaired electron, it can often be detected by electron spin resonance. From ESR spectra can be obtained structural information and kinetic information, information about the formation and decay of the radicals. To study the process of free radical generation is an important step towards reducing the deteriorating effects of oxidative stress.