Plants have an innate ability to biosynthesize a wide range of antioxidants capable of attenuating Reactive oxygen species (ROS) induced oxidative damage Plants. Most of the time, the production of free radicals is genetically planned since they function as signaling molecules. However, overproduction of free radicals can also sometimes damage biomolecules such as DNA, proteins and lipids.
Plants have efficient complex enzymatic and non-enzymatic antioxidant defense systems to avoid the toxic effects of free radicals.
Enzymatic Systems: include SOD, catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR).
Non-enzymatic systems: consist of low molecular weight antioxidants (ascorbic acid, glutathione, proline, carotenoids, phenolic acids, flavonoids, etc.) and high molecular weight secondary metabolites such as tannins
Low molecular weight antioxidants function as redox buffers that interact with numerous cellular components and influence plant growth and development. In addition, these antioxidants may influence gene expression associated with biotic and abiotic stress responses to maximize defense against microbial pathogens and animal herbivores.
Secondary metabolites as antioxidants:
Secondary metabolites provide passive and active resistance. In passive resistance, metabolites are continuously available, despite the presence of stressors, whereas in active resistance, metabolites are produced in response to specific stressors.
Among all secondary metabolites, phenolic antioxidants appear to be the most important. Plant phenolics are mainly classified into five major groups, phenolic acids, flavonoids, lignans, stilbenes and tannins. It has commonly been assumed that the antioxidant capacity of phenolics will increase with the number of free hydroxyls and conjugation of side chains to the aromatic rings. Moreover, they are known to interact with other physiological antioxidants such as ascorbate or tocopherol and to synergistically amplify their biological effects.
Antioxidants play an important role in fields as varied as:
Food quality and nutrition: Antioxidants play a major part in ensuring that food keep their taste and colour and remain edible over a longer period. Their use is particularly important for avoiding oxidation of fats and fat-containing products. Another important reason is that certain vitamins and various amino acids can easily be destroyed by exposure to air, and antioxidants serve to protect them. They also help to slow down the discoloration of fruit and vegetables.
Supplements: Antioxidant supplements or antioxidant containing foods may be used to prevent oxidative damage, and it can decrease the risk of many diseases, such us diabetes, heart complications, neurologic disorders, etc. Furthermore, the comsuption of antioxidants help to delay the aging process,and to support inmune system, among others.
Study of diseases: When the antioxidant protection is unbalanced by a series of factors, deterioration of physiological functions may occur, and in this way diseases and accelerated ageing can appear.
Stability measurement of extract products and nutracuticals: Plant extracts have many utilities due to their properties, so it is important to know the conditions of the extract to ensure that the extraction is stable.
Storage conditions testing: antioxidants protect against the oxdation of many compounds, so the sample can be kept longer.
Methods for the determination of antioxidant activity
Attending to the mechanism underlying the antioxidant– oxidant reaction, the methods were divided in hydrogen atom transfer (HAT) and single electron transfer (SET) techniques. HAT-based methods measure the capacity of an antioxidant to trap free radicals by hydrogen donation, while SET methods rely on the one-electron transfer reductive ability of an antioxidant compound versus a radical species.
There are many analytical methods for the determination of antioxidant activity reported that can be classified into several main categories: electroanalytical, chromatographic, spectroscopic and other methods.
There is a discrepancy in choosing the most adequate method, and it’s going to depend on the type of sample and what you want to measure. A quick and easy way to quantify the total amount of antioxidants is with ebqc-NI. This device is based on electrochemical technology, and it measures the antioxidant capacity in plant and vegetable extracts, directly. Furthermore, many samples extracted from plants have a lot of colors and it can interfere with the signal in colorimetric tests. With ebqc-ni, the measure has no interference with the color of the sample.
Based on the eBQC electrochemical technology: without radical initiators, it represents a measure of the global antioxidant status of the sample
Pisoschi, Aurelia Magdalena, Aneta Pop, Carmen Cimpeanu, and Gabriel Predoi. 2016. “Antioxidant Capacity Determination in Plants and Plant-Derived Products: A Review.” Oxidative Medicine and Cellular Longevity 2016 (ID 9130976): 36. https://doi.org/10.1155/2016/9130976
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