DNA damage in a solution containing copper(II) ions and ascorbic acid: Effect of the presence of sulfite

Some antioxidant compounds have a pro-oxidant effect in the presence of transition metal ions, due to the reduction of Mn+ to M(n-1)+ with simultaneous formation of free radicals, which then promote DNA damage. In the present study, we evaluated the pUC19 DNA damage in a solution containing Cu(II) and ascorbic acid (AA) or S(IV) saturated with air by agarose gel electrophoresis. Our results showed that this damage decreases if AA and S(IV) are simultaneously added. This study also illustrates the importance of Cu(II) in this process, as no DNA damage was observed when AA or S(IV) were present in the absence of this metallic ion. Our data showed that DNA preservation depends on the concentration of AA and S(IV) and occurs when the [S(IV)]:[AA] ratio ranges from 1:1 to 20:1. Absorbance measurements and thermodynamic data show that no reaction occurs between AA and S(IV) when this mixture (pH 5.5) is added to pUC-19 DNA. The presence of dissolved oxygen may be the cause of AA consumption in the mixture of these two antioxidants, which subsequently decreases DNA damage.

Actividad gastroprotectora, tamizaje fitoquímico y actividad atrapadora de radicales libres de Aloysia Gratissima (Verbenaceae) / Phytochemical screning, gastroprotective activity and free radical scavenging activity of Aloysia gratissima (Verbenaceae)

Se evaluó la actividad gastroprotectora de la infusión proveniente de las hojas de Aloysia gratissima (Verbenaceae), especie nativa de interés medicinal que se desarrolla en el sudoeste bonaerense, utilizando un modelo de inducción de úlceras gástricas con etanol en ratones. Se realizó un tamizaje fitoquímico para detectar la presencia de compuestos que podrían ser responsables de la actividad gastroprotectora de la planta. Se determinó el contenido de fenoles totales y la capacidad atrapadora de radicales libres mediante el método del Folin-Ciocalteu y del 2,2'-difenil-1-picrilhidrazilo (DPPH), respectivamente. Los ensayos demostraron que la infusión de la planta, administrada por vía oral en dosis de 100, 500 y 1000 mg/kg, ejerció una gastroprotección significativa frente a la inducción de úlceras. Se detectó una actividad atrapadora de radicales libres de 47,5%, similar a la sustancia de referencia (BHT). El estudio fitoquímico detectó la presencia de flavonoides y otros polifenoles, sustancias con reconocida capacidad antioxidante. Estos metabolitos ejercen efectos protectores en diferentes modelos experimentales de inducción de úlceras mediante mecanismos que pueden involucrar la neutralización de radicales libres, lo que podría explicar la actividad gastroprotectora de la planta. Estos hallazgos requieren estudios adicionales de A. gratissima como una posible terapia frente a la úlcera gástrica. (AU)

The gastroprotective activity of the infusion from the leaves of Aloysia gratissima (Verbenaceae), a native species of medicinal interest growing in South West Buenos Aires, was evaluated in an ethanol-induced gastric ulcer model in mice. Phytochemical screening was carried out in order to determine the presence of compounds that could be responsible for the pharmacological effects of the plant. Total phenolic content and the free radical scavenging activity of the plant were determined using the Folin-Ciocalteu and the 2,2'-diphenyl1-picrylhydrazyl (DPPH) method, respectively. Assays demonstrated that the infusion, orally administered at 100, 500, and 1000 mg/kg doses, exerted a significant gastroprotection effect against ulcer induction (P<0,05). A free radical scavenging activity of 47.5% -similar to the reference substance (BHT)- was detected. Phytochemical screening revealed the presence of antioxidant compounds such as flavonoids and other phenolic compounds. These compounds exert protective effects in different experimental models of ulcer induction that could involve free radical neutralization, which could explain the gastroprotective activity of the plant. These promising results support additional studies of A. gratissima as a potential therapy against gastric ulcer. (AU)

Estresse oxidativo: conceito, implicações e fatores modulatórios / Oxidative stress: concept, implications and modulating factors

O estresse oxidativo decorre de um desequilíbrio entre a geração de compostos oxidantes e a atuação dos sistemas de defesa antioxidante. A geração de radicais livres e/ou espécies reativas não radicais é resultante do metabolismo de oxigênio. A mitocôndria, por meio da cadeia transportadora de elétrons, é a principal fonte geradora. O sistema de defesa antioxidante tem a função de inibir e/ou reduzir os danos causados pela ação deletéria dos radicais livres e/ou espécies reativas não radicais. Esse sistema, usualmente, é dividido em enzimático (superóxido dismutase, catalase e glutationa peroxidase) e não-enzimático. No último caso, é constituído por grande variedade de substâncias antioxidantes, que podem ter origem endógena ou dietética. Objetivou-se revisar os principais mecanismos de geração de radicais livres, bem como a ação dos agentes mais relevantes do sistema de defesa antioxidante, ressaltando suas implicações sobre os marcadores do estresse oxidativo. Também serão abordados os principais fatores exógenos moduladores do estresse oxidativo.

There is evidence that oxidative stress, defined as a persistent imbalance between the production of highly oxidative compounds and antioxidant defenses, leads to tissue damage. Oxygen metabolism generates free radicals and/or non-radical reactive oxygen species. The mitochondria, through the electron transport chain, are the main generator of these species. The antioxidant defense system has the function of inhibiting and/or reducing the damage caused by the deleterious free radicals and/or non-radical reactive oxygen species. This system is divided into enzymatic (superoxide dismutase, catalase and glutathione peroxidase), and nonenzymatic. The nonenzymatic system consists of a variety of antioxidant substances, which may be endogenous or dietary. This study proposed to review the main mechanisms of reactive oxygen species generation and the role of the most relevant agents of the antioxidant defense system on the biomarkers of oxidative stress. The main exogenous factors that modulate oxidative stress will also be discussed.

Antioxidant activity of extract from Polygonum cuspidatum

Numerous diseases are induced by free radicals via lipid peroxidation, protein peroxidation and DNA damage. It has been known that a variety of plant extracts have antioxidant activities to scavenge free radicals. Whether Polygonum cuspidatum Sieb. et Zuce has antioxidant activity is unknown. In this study, dried roots of Polygonum cuspidatum were extracted by ethanol and the extract was lyophilized. Free radical scavenging assays, superoxide radical scavenging assays, lipid peroxidation assays and hydroxyl radical-induced DNA strand scission assays were employed to study antioxidant activities. The results indicate that the IC50 value oí Polygonum cuspidatum extract is 110 µg/ml in free radical scavenging assays, 3.2 µg/ml in superoxide radical scavenging assays, and 8 µg/ml in lipid peroxidation assays, respectively. Furthermore, Polygonum cuspidatum extract has DNA protective effect in hydroxyl radical-induced DNA strand scission assays. The total phenolics and flavonoid content of extract is 641.1 ± 42.6 mg/g and 62.3 ± 6.0 mg/g. The results indicate that Polygonum cuspidatum extract clearly has antioxidant effects.

The effects of DPPH on cochlear microcirculation / 华中科技大学学报（医学）（英德文版）

To investigate the effects of the free radical, 1,1-Diphenyl-2-picylhydrazyl, on cochlear blood flow, 20 guinea pigs were divided into 3 groups at random, 6 for control group, 6 for 1 mmol/L group and 8 for 0.1 mmol/L group. 2 microliters vehicle or drugs were dropped into round window membrane (RWM). Cochlear microcirculation was monitored by laser Doppler flowmeter (LDF), and mean arterial blood flow (MABP), which was transferred by pressure conductor sensor and preamplifier, was simultaneously recorded on the computer. Our results showed that MABP was stable throughout the experiment. Cochlear blood flow (CBF) increased by 10.32% (P < 0.05) in 1 mmol/L group, and decreased by 4.89% in 0.1 mmol/L group (P < 0.05). In control group cochlear microcirculation showed no significant changes. It is concluded that DPPH exerted effects on cochlear microcirculation.

A novel strategy of oxygen restriction by some diazotrophic enteric bacteria.

Protection of nitrogenase against oxygen inactivation in diazotrophs involves numerous strategies. Glutathione is known to play an important role in scavenging oxyradicals in many living systems. The involvement of glutathione (reduced) (GSH), glutathione peroxidase (GPX) and glutathione reductase (GR) in the protection of nitrogenase in free living diazotrophs is reported here for the first time. Reduced glutathione content and the activity of glutathione peroxidase and glutathione reductase increased with increase in oxygen concentration under nitrogen fixing conditions but decreased under anaerobic and nitrogenase repressed conditions. This correlation is used to postulate a protecting role for GSH-GPX-GR system against oxygen inactivation of nitrogenase.

Antioxidantes: mitos y realidades / Antioxidants: myths and reallity

La homeostasis de los seres vivos aeróbicos se ve constantemente amenazada por la formación de moléculas químicamente inestables y altamente reactivas llamadas radicales libres. Estos pueden generarse por agresores metabólicos endógenos (metabolismo celular) o exógenos, como el tabaco, el ozono y la radiación ultravioleta. Se les relaciona con una serie de condiciones patológicas, como la carcinogénesis, la aterosclerosis y el envejecimiento tisular. Los antioxidantes son sustancias que al interactuar con estos radicales libres previenen o demoran su acción deletérea. En la dieta se encuentran diversos compuestos que pueden contribuir a la modulación interna de los antioxidantes, apartándolos en forma directa o como cofactores. Es importante conocer estos antioxidantes dietarios, saber sus requerimientos mínimos y los potenciales riesgos por uso inapropiado

Estrés oxidativo, una enfermedad de nuestro tiempo: el beneficio de la suplementación de la dieta con sustancias antioxidantes / Oxidative stress, a recent disease: benefit of the dietary supplement with antioxidants

El oxígeno es fundamental para la gran mayoría de los organismos vivos, ya que participa en reacciones de oxidación que son a su vez fundamentales en el proceso de generación de energía, indispensable para la vida. Sin embargo, bajo ciertas circunstancias el consumo de oxígeno molecular puede desencadenar reacciones no controladas de oxidación, las que dañan la estructura y función de los organismos vivos, produciendo lo que se denomina un estrés oxidativo, proceso que se relaciona con diferentes enfermedades. Este fenómeno surge como consecuencia de un desequilibrio entre la actividad de los sistemas orgánicos de protección (sistema antioxidantes) y la agresión prooxidante derivada del medio ambiente, de la edad y de desequilibrios nutricionales. La alimentación cumple un papel fundamental para proveer antioxidantes a nuestro organismo, ya que muchas sustancias, principalmente de origen vegetal, son capaces de aportar una protección al desarrollo del estrés oxidativo, especialmente cuando las condiciones de vida del individuo han disminuido el potencial de sus sistemas antioxidantes

Physiology of aging.

Aging could be due to reduced ability to adapt to stress and/or aging of immune system. It is suggested that body cells (except germ cells and transformed cells) bear specific 'death' genes responsible for aging process. However, current concepts of free radicals (chemical intermediate) and aging, postulate that intermolecular linkages between degradation products of lipid oxidation (when free radical is a polysaturated fatty acid) results in inactive polymers interfering with cell activity which could be inactivated by natural or artificial antioxidants (e.g. vit.E, vit.C) With aging body composition and conformation changes resulting in diminished activity of vital organs and structural changes in the body involving skin, muscle, bones etc. with altered look, diminished movements, hearting, vision etc. However, changes in higher function cause decline in intelligence, memory, ability to take decision, slow reaction and decrease ability to learn new skills resulting in more rigid attitude in elderly. Balanced diet plays an important role in delaying aging process and sexual activity promotes active life span.

Evaluation of the hepatoprotective effect of some drugs in paracetamol-induced liver cell toxicity in the rat

This study aimed to clarify the hepatocellular injury induced by paracetamol and the possible hepatoprotective effect of fructose, cocktail of fructose, cyclosporin A and trifluoperazine, Nigella sativa oil, vitamin C and vitamin E

Radicais Livre / Free Radicals

Os autores fazem revisäo e atualizaçäo dos radicais livres e sua influência na fisiologia e patologia humana