Phenols, antioxidant activity

Pomegranate Phenolic Antioxidant Activities Protect against Cardiovascular Diseases... 

Litwinienko et al. (1997) reported that non-isothermal (conventional) DSC and P-DSC analyses can evaluate antioxidant activity in linolenic (Ci8 3) acid doped with phenolic antioxidants. Activation energies were inferred by applying the Ozawa-Flynn-Wall analytical method. Results showed that increasing BHT loading from 0.3 to 4.0mM increased the activation energy of oxidation from 73.0 to 97.8kJ/mol. 

The phenolic antioxidant activity in the corn oil emulsions of 17 selected Spanish wines and two Californian wines was examined for their preventive capability for lipid oxidation as dietary antioxidants. The inhibition of hydroperoxide formation [measured as percent of control for 10 iM gallic acid equivalents (GAE)] was increased from 8.4 to 40.2% in the presence of the red wines, from 20.9 to 45.8% with the rose wines, and from 6.5 to 47.0% with the white wines. The inhibition of hydroperoxide formation at 20 xM GAE was increased from 11.9 to 34.1% in the presence of red wines, from 0.1 to 34.5% with the rose wines, and from 3.3 to 37.2% with the white wines. The inhibition of the hexanal formation at 10 (jlM GAE was increased from 23.6 to 64.4% in the presence of red wines, from 42.7 to 68.5% with the rose wines, and from 28.4 to 68.8% with the white wines. Moreover, the inhibition of the hexanal formation at 20 xM GAE was increased from 33.0 to 46.3% in the presence of red wines, from 11.3 to 66.5% with the rose wines, and from - 16.7 to + 21.0% with the white wines. The antioxidant effect declined apparently with increasing concentration. The antioxidant activity might be ascribed to the five main groups of phenolics identified in the wines benzoic acids, anthocyanins, flavan-3-ols, flavonols, and hexanal [38]. 

Natural phenolic antioxidative activity is an additional benefit in the use of these smoke flavourings. The higher boiling point phenolics, in particular, possess antioxidative functionality similar to that of commercially used synthetic phenolic antioxidants. 

Total Phenols, Antioxidant Activity Protein Analysis... 

Variety Total Phenols Antioxidant Activity Protein ... 

Vattem DA, Shetty K. EUagic acid production and phenolic antioxidant activity in cranberry pomace Vaccinium macrocarpon) mediated by Lentinus edodes using a solid-state system. Process Biochem 2003 39 367-79. 

Long-chain esters of pentaerythritol have been prepared by a variety of methods. The tetranonanoate is made by treatment of methyl nonanoate [7289-51-2] and pentaerythritol at elevated temperatures using sodium phenoxide alone, or titanium tetrapropoxide in xylene (12). PhenoHc esters having good antioxidant activity have been synthesized by reaction of phenols or long-chain aUphatic acids and pentaerythritol or trimethyl olpropane (13). 

Although aminyl radicals are stable towards oxygen, they can oxidi2e other aromatic amines, phenols and thiols (10), and regenerate the diarylamine. Thus, mixtures of phenols and diarylamines frequendy show better antioxidant activity than either one alone. This is called synergism. 

The effect substitution on the phenolic ring has on activity has been the subject of several studies (11—13). Hindering the phenolic hydroxyl group with at least one bulky alkyl group ia the ortho position appears necessary for high antioxidant activity. Neatly all commercial antioxidants are hindered ia this manner. Steric hindrance decreases the ability of a phenoxyl radical to abstract a hydrogen atom from the substrate and thus produces an alkyl radical (14) capable of initiating oxidation (eq. 18). 

The antioxidative activities of polymeric antioxidants prepared from Verona oil and the conventional phenolic antioxidant 3-(3,5-di-terf-butyl-4-hydroxyphenyl)propionic acid (DTBH), chemically grafted to polystyrene and polyurethanes, is similar and in some cases even better than that of the corresponding low-MW phenolic antioxidants [81]. 

In addition to phenolic substances, there are other components present in foods which have no antioxidant activity of their own, but which increase that of phenolic antioxidants. They are called synergists, and they should be accounted for in any discussion of antioxidant activity. Polyvalent organic acids, amino acids, phospholipids (lecithin) and various chelating agents belong to this group. Proteins may modify the efficiency of antioxidants as they react with the reaction products of both antioxidants and synergists. 

It is not only lipids but also essential oils which are sensitive to oxidative changes on storage. Sometimes stabilised by synthetic or natural antioxidants, they usually contain substances showing moderate antioxidant activity, but these may be lost by evaporation or oxidised by air oxygen unless more powerful phenolic antioxidants are added. 

Table 16.1 Thermodynamic and kinetic parameters for plant phenols of relevance for their antioxidant capacity and antioxidant activity... 

MbFe(IV)=0 and with lipid peroxyl radicals (Castellucio et al, 1995). It may accordingly be concluded that the most relevant single parameter for predicting the antioxidative activity of a new plant phenol would be the standard reduction potential, E . 

PEYRAT-MAiLLARD M N, BONNELY s and BERSET c (2000) Determination of the antioxidant activity of phenolic compounds by coulometric detection, Talanta, 51, 709-16. 

RICE-EVANS c A, MILLER N J and PAGANGA G (1996) Structure-antioxidant activity relationships of flavonoids and phenolic acids, Free Rad Biol Med, 20, 933-56. 

Paganga, G. et al.. The polyphenolic content of fruit and vegetables and their antioxidant activities what does a serving constitute Free Radical Res., 30, 153, 1999. Maatta, K.R. et al.. High-performance liquid chromatography (HPLC) analysis of phenolic compounds in berries with diode array and electrospray ionization mass spectrometric (MS) detection Rihes species, J. Agric. Food Chem., 51, 6736, 2003. 

Results obtained in in vivo and ex vivo experiments are of various types. Some studies have found positive effects of the consumption of carotenoids or foods containing carotenoids on the markers of in vivo oxidative stress, even in smokers. Other studies demonstrated no effects of carotenoid ingestion on oxidative stress biomarkers of lipid peroxidation. " It should be noted that for studies using food, the activity observed may also be partly due to other antioxidant molecules in the food (phenols, antioxidant vitamins) or to the combination of actions of all the antioxidants in the food. 

Wada, L. and On, B., Antioxidant activity and phenolic content of Oregon caneberries, J. Agric. Food Chem., 50, 3495, 2002. 

GhiseUi, A. et al.. Antioxidant activity of different phenolic fractions separated from an Italian red wine, J. Agric. Eood Chem., 46, 361, 1998. 

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