Lycopene antioxidant activity

It has been established that carotenoid structure has a great influence in its antioxidant activity for example, canthaxanthin and astaxanthin show better antioxidant activities than 3-carotene or zeaxanthin. 3- 3 3-Carotene also showed prooxidant activity in oil-in-water emulsions evaluated by the formation of lipid hydroperoxides, hexanal, or 2-heptenal the activity was reverted with a- and y-tocopherol. Carotenoid antioxidant activity against radicals has been established. In order of decreasing activity, the results are lycopene > 3-cryptoxanthin > lutein = zeaxanthin > a-carotene > echineone > canthaxanthin = astaxanthin. ... 

Fruifs and vegetables also contain ofher bioactive substances such as polyphenols (including well-known pigments anthocyanins, flavonols) and non-provitamin A carotenoids (mainly lycopene, lutein, and zeaxanthin) that may have protective effects on chronic diseases. Polyphenols and carotenoids are known to display antioxidant activities, counteracting oxidative alterations in cells. Besides these antioxidant properties, these colored bioactive substances may exert other actions on cell signaling and gene expression. 

Takeoka, G.R., Processing effects on lycopene content and antioxidant activity of tomatoes, J. Agric. Food Chem., 49, 3713, 2001. 

Tomato was reported to exert antioxidant activity in some studies (Vinson and others 1998 Kahkonen and others 1999), whereas it showed no antioxidant activity or even acted as a pro-oxidant in others (Gazzani and others 1998). The antioxidant effect of tomato is most probably due to synergism between several compounds and not due to lycopene content alone, as pure lycopene and several other carotenoids act as pro-oxidants in a lipid environment (Al-Saikhan and others 1995 Haila and others 1996). 

The antioxidant activity of carotenoids depends on the number of conjugated double bonds and possibly the presence of oxygenated functions in the molecule (Schmidt 2004). The high antioxidant activity of lycopene has been identified against singlet... 

Martinez-Valverde I, Periago MJ, Provan G and Chesson A. 2002. Phenolic compunds, lycopene and antioxidant activity in commercial varieties of tomato (Lycopersicum esculentum). J Sci Food Agric 82(3) 323-330. 

Lycopene, the predominant carotenoid in tomatoes (Solatium lycopersicum), exhibits the highest antioxidant activity and singlet oxygen quenching ability of all dietary... 

Andreassi, M. etal., Antioxidant activity of topically applied lycopene, J. Eur. Acad. Dermatol. 

Taping Z, Suping Q, Werdi Y, Zheng X, Hong S, Side Y, Dapu W. (2002) Antioxidant activity of lycopene extracted from tomato paste towards trichloromethyl peroxyl radical. Food Chemistry 77 209-212. 

The concentrations of carotenoids and the level of oxygen they are exposed to can also influence their antioxidant activities. At low oxygen partial pressures, diverse carotenoids effectively inhibit in vitro oxidation reactions, and their antioxidative abilities increase with increasing carotenoid concentration." " As oxygen levels are increased, however, their antioxidant potential typically decreases." " Certain carotenoids, notably P-carotene but also lycopene, exhibit unusual behavior beyond a threshold carotenoid concentration, they actually decrease in antioxidant ability with increasing carotenoid concentration, and this effect is further exacerbated at high oxygen levels." This prooxidant... 

Woodall et al. suggested that the different reactivities of the carotenoids against free radicals can be partly attributed to the differences in electron distribution along the polyene chain of different chromophores that would alter the susceptibility of free radical addition to the conjugated double bond system. However, other factors must be also considered. Stearic hindrance, hydrogen abstraction from the allylic position to the polyene chain (C-4 of P-carotene and its derivatives, end of lycopene), would reduce radical scavenging activity. In addition, the stability of the polyene radical is important in determining the rate of the loss of carotenoids and hence it affects their antioxidant activity. 

In the same oxidation system, an enhanced antioxidant activity of carotenoid mixtures (lutein, lycopene, paprika, bixin, etc.) have been reported as compared to each separate compound. Moreover, Kiokias and Gordon found that mixtures of olive oil phenolics with various carotenoids exhibited a strong activity against the autoxidation of bulk and emulsified olive oil, whereas individual carotenoids presented no inhibitory effect. 

Tomato (Solarium lycopersicwn L.) is extensively cultivated worldwide, and its fruits have assumed the status of functional foods as a result of epidemiological evidence of reduced risks of certain types of cancers and cardiovascular diseases [180,181]. They are a reservoir of diverse antioxidant molecules, such as lycopene, ascorbic acid, vitamin E, carotenoids, flavraioids, and phenolics, and may provide a significant part of the total intake of beneficial phytochemicals, as a result of then-high consumption rates. Among carotenoids, lycopene has a strong antioxidant activity and is able to induce cell-to-ceU communications and modulate hormones, immune systems, and other metabolic pathways [182]. 

Provitamins A exhibit anticarcinogenic effects, because they are part of the control mechanisms that scavenge free radicals (toxic forms of oxygen). Their antioxidant potential is relatively low. Other carotenoids that do not act as provitamins A have significantly higher antioxidant activities, such as lycopene, zeaxanthin and lutein. The enzymes that oxidise fatty acids (lipoxygenases or linoleate O2 oxidoreductases, formerly known as Kpoxidases) are antivitamins A. 

The relative antioxidant activities of carotenoids in multilamellar liposomes, as assayed by inhibition of the formation of thiobarbituric acid-reactive substances (TBARs), were lycopene>a-carotene>p-cryptoxanthin >zeaxanthin= P-carotene>lutein (Stahl et al, 1998). Mixtures of carotenoids were more effective than the single compounds, and this synergistic effect was most pronounced when lycopene or lutein was present. The superior antioxidant activity of mixtures of carotenoids may be related to the specific positioning of different carotenoids within cell membranes. 

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