Comparative Study on Antioxidant Activity of Lycopene (Z)-Isomers in Different Assays

Abstract

Several studies have implicated the potent antioxidant properties of lycopene. However, most of the studies used only the (all-E)-isomer. (Z)-Isomers of lycopene were found in substantial amounts in processed foods and in human tissues. In the present study, we investigated in vitro the antioxidant activity of (5Z)-, (9Z)-, and (13Z)-lycopene compared to the (all-E)-isomer. Additionally, prolycopene, the (7Z,9Z,7'Z,9'Z)-isomer found in tangerine tomatoes, was analyzed. No significant differences were found between the isomers in ferric reducing antioxidant power assay and in bleaching the radical cation of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), both based on ET mechanisms. In contrast, scavenging activity against peroxyl radicals generated by thermal degradation of 2,2'-azobis(2-amidinopropane) (AAPH) was higher in the (Z)-isomers. (5Z)-Lycopene was most antioxidant in scavenging lipid peroxyl radicals, evaluated by analyzing the inhibition of MbFe(III) lipid peroxidation of linoleic acid in mildly acidic conditions (pH 5.8) in a micellar environment, modeling a possible antioxidant action in the gastric compartment.

Complex interactions between dietary and genetic factors impact lycopene metabolism and distribution

“…Based on the prevalence of lycopene cis isomers in plasma and tissues [23], emerging evidence suggesting their greater antioxidant potential than trans lycopene [36], and their hypothesized role as a preferred substrate for beta-carotene 9′,10′ dioxygenase 2 (BCDO2; an enzyme responsible for eccentric cleavage of carotenoids, discussed later) [37], future investigations should seek to describe the metabolism of cis versus trans lycopene. Based on the heterogeneity observed in these limited studies, this area of research could benefit from larger sample sizes, the use of isotopically-labeled tracer lycopene, and accounting for relevant genetic variation.…”

Adverse effects in broiler chickens fed a high lycopene concentration supplemented diet

“…Lycopene and others carotenoids have been shown to act as prooxidants or antioxidants, depending on the dose at which they are administered. Many studies have reported the antioxidant effect of lycopene both in vivo (Sahin et al 2006) and in vitro (Shi et al 2007;Mu¨ller et al 2011), although the dose-dependent pro-oxidant effect has only been shown in vitro (Lowe et al 1999;Yeh and Hu 2000). It has been demonstrated that supplemented beta-carotene and other carotenoids are oxidatively degraded under heavy oxidative stress, which leads to the formation of high amounts of breakdown products with pro-oxidant properties (Siems et al 2005).…”

Lipid/detergent mixed micelles as a tool for transferring antioxidant power from hydrophobic natural extracts into bio-deliverable liposome carriers: the case of lycopene rich oleoresins

“…(all-E)-Lycopene dispersed in POPC/cholate micelles exhibited an antioxidant power around 11 times higher than Trolox (TEAC ¼ 10.8). A lower antioxidant capacity of (all-E)-lycopene (a-TEAC ¼ 4) was recently reported by Muller et al, 46 who employed a two-phase water-n-hexane ABTSc + decolourization assay, analogue to that one adopted for LRO analysis. However these authors read the decolourization 2 min aer lycopene/ABTS mixing, thus determining a "fast" a-TEAC value.…”