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      Free radicals, antioxidants and functional foods: Impact on human health

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          Abstract

          In recent years, there has been a great deal of attention toward the field of free radical chemistry. Free radicals reactive oxygen species and reactive nitrogen species are generated by our body by various endogenous systems, exposure to different physiochemical conditions or pathological states. A balance between free radicals and antioxidants is necessary for proper physiological function. If free radicals overwhelm the body's ability to regulate them, a condition known as oxidative stress ensues. Free radicals thus adversely alter lipids, proteins, and DNA and trigger a number of human diseases. Hence application of external source of antioxidants can assist in coping this oxidative stress. Synthetic antioxidants such as butylated hydroxytoluene and butylated hydroxyanisole have recently been reported to be dangerous for human health. Thus, the search for effective, nontoxic natural compounds with antioxidative activity has been intensified in recent years. The present review provides a brief overview on oxidative stress mediated cellular damages and role of dietary antioxidants as functional foods in the management of human diseases.

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          Most cited references83

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          Glutathione transferases.

          This review describes the three mammalian glutathione transferase (GST) families, namely cytosolic, mitochondrial, and microsomal GST, the latter now designated MAPEG. Besides detoxifying electrophilic xenobiotics, such as chemical carcinogens, environmental pollutants, and antitumor agents, these transferases inactivate endogenous alpha,beta-unsaturated aldehydes, quinones, epoxides, and hydroperoxides formed as secondary metabolites during oxidative stress. These enzymes are also intimately involved in the biosynthesis of leukotrienes, prostaglandins, testosterone, and progesterone, as well as the degradation of tyrosine. Among their substrates, GSTs conjugate the signaling molecules 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2) and 4-hydroxynonenal with glutathione, and consequently they antagonize expression of genes trans-activated by the peroxisome proliferator-activated receptor gamma (PPARgamma) and nuclear factor-erythroid 2 p45-related factor 2 (Nrf2). Through metabolism of 15d-PGJ2, GST may enhance gene expression driven by nuclear factor-kappaB (NF-kappaB). Cytosolic human GST exhibit genetic polymorphisms and this variation can increase susceptibility to carcinogenesis and inflammatory disease. Polymorphisms in human MAPEG are associated with alterations in lung function and increased risk of myocardial infarction and stroke. Targeted disruption of murine genes has demonstrated that cytosolic GST isoenzymes are broadly cytoprotective, whereas MAPEG proteins have proinflammatory activities. Furthermore, knockout of mouse GSTA4 and GSTZ1 leads to overexpression of transferases in the Alpha, Mu, and Pi classes, an observation suggesting they are part of an adaptive mechanism that responds to endogenous chemical cues such as 4-hydroxynonenal and tyrosine degradation products. Consistent with this hypothesis, the promoters of cytosolic GST and MAPEG genes contain antioxidant response elements through which they are transcriptionally activated during exposure to Michael reaction acceptors and oxidative stress.
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            Superoxide dismutase multigene family: a comparison of the CuZn-SOD (SOD1), Mn-SOD (SOD2), and EC-SOD (SOD3) gene structures, evolution, and expression.

            Superoxide dismutases are an ubiquitous family of enzymes that function to efficiently catalyze the dismutation of superoxide anions. Three unique and highly compartmentalized mammalian superoxide dismutases have been biochemically and molecularly characterized to date. SOD1, or CuZn-SOD (EC 1.15.1.1), was the first enzyme to be characterized and is a copper and zinc-containing homodimer that is found almost exclusively in intracellular cytoplasmic spaces. SOD2, or Mn-SOD (EC 1.15.1.1), exists as a tetramer and is initially synthesized containing a leader peptide, which targets this manganese-containing enzyme exclusively to the mitochondrial spaces. SOD3, or EC-SOD (EC 1.15.1.1), is the most recently characterized SOD, exists as a copper and zinc-containing tetramer, and is synthesized containing a signal peptide that directs this enzyme exclusively to extracellular spaces. What role(s) these SODs play in both normal and disease states is only slowly beginning to be understood. A molecular understanding of each of these genes has proven useful toward the deciphering of their biological roles. For example, a variety of single amino acid mutations in SOD1 have been linked to familial amyotrophic lateral sclerosis. Knocking out the SOD2 gene in mice results in a lethal cardiomyopathy. A single amino acid mutation in human SOD3 is associated with 10 to 30-fold increases in serum SOD3 levels. As more information is obtained, further insights will be gained.
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              Diversity of structures and properties among catalases.

              More than 300 catalase sequences are now available, divided among monofunctional catalases (> 225), bifunctional catalase-peroxidases (> 50) and manganese-containing catalases (> 25). When combined with the recent appearance of crystal structures from at least two representatives from each of these groups (nine from the monofunctional catalases), valuable insights into the catalatic reaction mechanism in its various forms and into catalase evolution have been gained. The structures have revealed an unusually large number of modifications unique to catalases, a result of interacting with reactive oxygen species. Biochemical and physiological characterization of catalases from many different organisms has revealed a surprisingly wide range of catalatic efficiencies, despite similar sequences. Catalase gene expression in micro-organisms generally is controlled either by sensors of reactive oxygen species or by growth phase regulons, although the detailed mechanisms vary considerably.
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                Author and article information

                Journal
                Pharmacogn Rev
                PRev
                Pharmacognosy Reviews
                Medknow Publications & Media Pvt Ltd (India )
                0973-7847
                0976-2787
                Jul-Dec 2010
                : 4
                : 8
                : 118-126
                Affiliations
                [1] Department of Botany, Birla College, Kalyan – 421 304, Maharastra, India.
                Author notes
                Address for correspondence: Mrs. Vijaya Chavan Lobo, Department of Botany, Birla College, Kalyan - 421 301, India. E-mail: vijayalobo@ 123456rediffmail.com
                Article
                PRev-4-118
                10.4103/0973-7847.70902
                3249911
                22228951
                77222829-4ce5-453a-ba69-64b5400e8f20
                Copyright: © Pharmacognosy Reviews

                This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 04 March 2010
                : 08 March 2010
                Categories
                Review Article

                Pharmacology & Pharmaceutical medicine
                antioxidant,ageing,oxidative stress,free radicals
                Pharmacology & Pharmaceutical medicine
                antioxidant, ageing, oxidative stress, free radicals

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