Oxidative stress is a phenomenon caused by an imbalance between production and accumulation of oxygen reactive species (ROS) in cells and tissues and the ability of a biological system to detoxify these reactive products. ROS can play, and in fact they do it, several physiological roles (i.e., cell signaling), and they are normally generated as by-products of oxygen metabolism; despite this, environmental stressors (i.e., UV, ionizing radiations, pollutants, and heavy metals) and xenobiotics (i.e., antiblastic drugs) contribute to greatly increase ROS production, therefore causing the imbalance that leads to cell and tissue damage (oxidative stress). Several antioxidants have been exploited in recent years for their actual or supposed beneficial effect against oxidative stress, such as vitamin E, flavonoids, and polyphenols. While we tend to describe oxidative stress just as harmful for human body, it is true as well that it is exploited as a therapeutic approach to treat clinical conditions such as cancer, with a certain degree of clinical success. In this review, we will describe the most recent findings in the oxidative stress field, highlighting both its bad and good sides for human health.

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Oxidative Stress: Harms and Benefits for Human Health

https://bibliotecadigital.ipb.pt/bitstream/10198/8534/4/Ferreira%20FCT-D-12-01230%20Word%20original%20%20%20edits%20revised.pdf

A review on antioxidants, prooxidants and related controversy: natural and synthetic compounds, screening and analysis methodologies and future perspectives.

Phenolic compounds including phenolic acids, flavonoids and proanthocyanidins are widely distributed in plants as a protective mechanism against biotic and abiotic stresses. Fruits, vegetables, grains, spices and herbs are the richest source of dietary polyphenols. High intake of these foods has been linked to lowered risk of most common degenerative and chronic diseases that are known to be caused by oxidative stress. This review intends to summarize briefly recent progress on the chemistry and biochemistry of dietary polyphenols, their antioxidant and anti-inflammatory activities, and the underlying molecular mechanisms of their involvement in inflammation mediated metabolic diseases are also discussed. Perspectives for future research are also briefly discussed.

Dietary polyphenols, oxidative stress and antioxidant and anti-inflammatory effects

Antioxidants are substances that may protect cells from the damage caused by unstable molecules such as free radicals. Flavonoids are phenolic substances widely found in fruits and vegetables. The previous studies showed that the ingestion of flavonoids reduces the risk of cardiovascular diseases, metabolic disorders, and certain types of cancer. These effects are due to the physiological activity of flavonoids in the reduction of oxidative stress, inhibiting low-density lipoproteins oxidation and platelet aggregation, and acting as vasodilators in blood vessels. Free radicals are constantly generated resulting in extensive damage to tissues leading to various disease conditions such as cancer, Alzheimer's, renal diseases, cardiac abnormalities, etc., Medicinal plants with antioxidant properties play a vital functions in exhibiting beneficial effects and employed as an alternative source of medicine to mitigate the disease associated with oxidative stress. Flavonoids have existed over one billion years and possess wide spectrum of biological activities that might be able to influence processes which are dysregulated in a disease. Quercetin, a plant pigment is a potent antioxidant flavonoid and more specifically a flavonol, found mostly in onions, grapes, berries, cherries, broccoli, and citrus fruits. It is a versatile antioxidant known to possess protective abilities against tissue injury induced by various drug toxicities.

Overviews of Biological Importance of Quercetin: A Bioactive Flavonoid.

Oxidative stress plays an essential role in the pathogenesis of chronic diseases such as cardiovascular diseases, diabetes, neurodegenerative diseases, and cancer. Long term exposure to increased levels of pro-oxidant factors can cause structural defects at a mitochondrial DNA level, as well as functional alteration of several enzymes and cellular structures leading to aberrations in gene expression. The modern lifestyle associated with processed food, exposure to a wide range of chemicals and lack of exercise plays an important role in oxidative stress induction. However, the use of medicinal plants with antioxidant properties has been exploited for their ability to treat or prevent several human pathologies in which oxidative stress seems to be one of the causes. In this review we discuss the diseases in which oxidative stress is one of the triggers and the plant-derived antioxidant compounds with their mechanisms of antioxidant defenses that can help in the prevention of these diseases. Finally, both the beneficial and detrimental effects of antioxidant molecules that are used to reduce oxidative stress in several human conditions are discussed.

/pdf/lifestyle-oxidative-stress-and-antioxidants-back-and-forth-27lvucs2ay.pdf

Lifestyle, Oxidative Stress, and Antioxidants: Back and Forth in the Pathophysiology of Chronic Diseases.

Antioxidant and prooxidant properties of flavonoids.

Exploring patterns and causes of intraspecific trait variation is crucial for a better understanding of the effects of climate change on plant populations and ecosystems. However, our current understanding of the intraspecific trait variation is mainly based on structural (morphological) traits, and we have limited knowledge on patterns and causes of variation in biochemical traits (e.g., leaf pigments), which are also crucial for plant adaptation. As a result, we also do not know how similar the climatic effects on structural versus biochemical traits are. Using plant traits from 110 genotypes representing 11 Festuca rubra populations grown in 4 different climates, we studied trait covariation among structural traits (linked to fitness, resource use, gas exchange, and reproduction) and biochemical traits (linked to photosynthesis, photoprotection, and oxidative stress). We also disentangled the relative role of the climate of origin and the climate of cultivation in the structural versus biochemical traits and tested for adaptive plasticity in the traits. We found that 1) biochemical traits did not covary with structural traits and represent independent ‘photoharvesting – photoprotection’ strategy dimension of functional variation; 2) interactive effects of climate of origin and cultivation were more pronounced for biochemical than structural traits. 3) Trait plasticity was affected by the climate of origin (precipitation and temperature as well as their interaction); 4) F. rubra showed both adaptive and mal-adaptive plasticity, and adaptiveness depended upon trait type, cultivation climate, and climate of origin. Overall, our results suggest that structural and biochemical plant traits respond differentially to climate and thus the response of one group of traits cannot be predicted from the other. Responses are also strongly determined by interactions between the climate of origin and cultivation. Thus, more studies on variation in biochemical traits, their correspondence to other traits, and their variation with climate are needed.

Differential effect of climate on structural and biochemical plant traits

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/1365-2435.14291

N. Wilhelmová

Papers

Antioxidant and prooxidant properties of flavonoids.

Differential effect of climate on structural and biochemical plant traits

Differential effect of climate of origin and cultivation climate on structural and biochemical plant traits