Antioxidative efficacy

Various types of cell-based in vitro studies have shown that carotenoids can exert prooxidant effects under certain conditions. Most of these studies show in fact decreases in antioxidant efficacy of carotenoids with increasing carotenoid concentration examples of true prooxidant effects are rarer. It is also important to pay attention to the experimental conditions and their biological relevance. Indeed, carotenoids have sometimes been proven to (I) exert prooxidant activity in an atmosphere of pure oxygen, (2) never occur in vivo, or (3) appear in concentrations that they would never reach in vivo. 

New toxicological data on some of the synthetic antioxidants cautioned against their use. In the recent past, natural antioxidants attracted the attention of many food manufacturers as a result of the necessity to produce healthy foods. Numerous antioxidative efficacious compounds that are found in animal or plant tissues and that are also available as synthetic molecules are used in several food applications. Herbs and spices occupy a special position in foods as traditional food ingredients and hence are appropriately used directly for their antioxidant characteristics. If they are applied to foods, they do not need to be declared as antioxidants. 

Mitchell JH, Gardner PT, Mcphail DB et al. Antioxidant efficacy of phytoestrogens in chemical and biological model systems. Arch. Biochem. Biophys. 360, 142-148, 1998. 

Examination of 3-indolyl compounds for relationships between antioxidation potential (using in vitro LP assays) and electronic, polar, and steric parameters, including bond dissociation energies, bond lengths, dipole moments, electronic charge densities, and molecular size parameters showed that antioxidant efficacy of 3-indolyl compounds was most strongly predicted... 

Vijayakumar, R.S., Surya, D. and Nalini, N. (2004) Antioxidant efficacy of black pepper (Piper nigrum L.) and piperine in rats with high fat diet induced oxidative stress. Redox Reporter 9(2), 105-110. 

One danger is that because herbal medications are not regulated, few if any clinical trials are performed even for safety or efficacy. One example is bilberry. Bilberry fruit is used to treat diabetes and diabetic retinopathy. Although animal models support the antioxidant role in vasoprotection, no well-designed and conducted clinical trials exist.The antioxidant effect may have benefit in AMD, as well. The antioxidant efficacy in bilberry is likely due to the tannin content, which is also found in grapes. 

Antioxidant activity of a given compound is assessed as resistance to oxidation of lipids in the presence of that particular compound. Therefore, most of the methods described and used to assess antioxidant activity follow oxidation and the stages of oxidation of unsaturated lipid substrates. Many techniques have been developed to determine the antioxidant efficacy of the compounds of interest, but all of these have to be employed and interpreted carefully. Frankel (19, 46) has listed following parameters that are fairly important in choosing methods to evaluate antioxidants. 

Besides scavenging peroxyl radicals, tocopherols and tocotrienols are also excellent quenchers for singlet oxygen and peroxynitrile (39). It has been reported that ot-tocopherol shows a pro-oxidant activity when present at high concentrations (106-108). It was later found that tocopherols do not show a pro-oxidant effect if they are compared with controls devoid of them and other lipid-related antioxidants (109, 110). However, tocopherols lose their antioxidant efficacy at high concentrations because they participate in a number of reactions that lead to production of alkoxyl radicals that consume tocopherols and initiate new reaction chains because of their low selectivity (111, 112). Using a kinetic approach, a number of reactions were found to contribute to the loss of tocopherol antioxidant activity that is greater for a-tocopherol than for y-tocopherol (113). 

Hung LM, Su MJ, Chu WK, Chiao CW, Chan WF, Chen JK. The protective effect of resveratrols on ischaemia-reperfusion injuries of rat hearts is correlated with antioxidant efficacy. Br J Pharmacol 2002 135 1627-1633. 

Phenolics are commonly present in both edible and inedible parts of plants. They act as antioxidants in food systems in order to minimize rancidity and protect cells from oxidative stress in the body. With the growing interest in replacing synthetic antioxidants with natural alternatives, many plant materials including tree nuts have been explored for their phenolic contents and antioxidant efficacies. A variety of phenolic compounds such as phenolic acids, llavonoids, and olher polyphenols have been isolated from almond and identified (Table 8.1). 

Sonaje K, Italia JL, Sharma G, Bhardwaj V, Tikoo K, Kumar MNVR. Development of biodegradable nanoparticles for oral delivery of ellagic acid and evaluation of their antioxidant efficacy against cyclosporine A-induced nephrotoxicity in rats. Pharm Res. 2007 24(5) 899-908. 

D. Chatteijee, P. Bhattacharjee, Comparative evaluation of the antioxidant efficacy of encapsulated and un-encapsulated eugenol-rich clove extracts in soybean oil Shelf-life and frying stability of soybean oil. J. Food Eng. 117, 545-550 (2013)... 

C11-B0DIPY (boron dipyrromethene difiu-oride) is a fluorescent ratio probe for indexing hpid peroxidation and antioxidant efficacy in model membrane systems and hving cells, with excellent characteristics (Drummen et al. 2002) ... 

SIA (4-Hydroxy-3,5-Dimethoxy-Cinnamic Acid) (Fig. 63.2) is a phenylpropanoid compound found in various herbal materials and high-bran cereals. It has been reported that sinapic acid has antioxidant efficacy as a metal chelator due to the orientation of functional groups. Administration of sinapic acid exhibited significant reversal of arsenic-induced toxicity in hepatic tissue [68]. 

Comparative evaluation of OIT indicators for PUE, stabilized by pen-taerythritol tetrakis[3-(3 ,5 -di-tert-butyl-4 -hydroxyphenyl)propionate], depending on the manufacturer, ceteris paribus, revealed significant difference in terms of the protective effect of sterically hindered phenol. In practical terms, this means that prior to making the composition and selecting the stabilizer, as well as planning direct qualitative and quantitative replacement of one brand stabilizer by another in the PUE, one must take into consideration the potential significant differences in antioxidant efficacy of the products. 

There has been considerable interest in recent years in the cytoprotective and neuroprotective effeets of flavonoids, especially in the context of their modes of action as antioxidants. The eleetron-donating properties of flavonoids are well defined to explain their antioxidant properties in vitro [10-14]. Structurally important features defining the reduction potential of flavonoids are the hydroxy-lation pattern, a 3, 4 -dihydroxy eatechol structure in the B-ring, the planarity of the molecule, and the presenee of 2,3 unsaturation in conjugation with a 4-oxo-function in the C-ring. Many studies have described the antioxidant efficacy of flavonoids and demonstrated that these polyphenols can inhibit the oxidation of lipids [12,15,16] and other biomolecules such as proteins and DNA [17-19] in... 

Poomima G, Keknda PTR, Vinayaka KS (2012) Antioxidant efficacy of Olea dioica Roxb (Oleaceae) leaves. Biomedicine 32 506-510... 

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