Do Apo-Lycopenoids Have Antioxidant Activities In Vitro?

Lycopene is a predominant carotenoid in human plasma and may prevent degenerative diseases by antioxidant mechanisms. Moreover, not only lycopene itself, also its derived breakdown products, the apo-lycopenoids, could be responsible. Therefore, we analyzed the in vitro antioxidant activities of apo-6′-, apo-8′- and apo-12′-lycopenals, as well as of apo-10′-, apo-14′- and apo-11-series of lycopene (with terminal functions as alcohol, aldehyde, carboxylic acid, and ester) in various assays. We observed that the antioxidant activities, determined by measuring the ferric reducing antioxidant power (FRAP assay), the activities of bleaching 2,2′-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS^·+) and the activities to scavenge peroxyl radicals (LPSC assay), were often much lower compared to lycopene itself, as recently proposed by some authors. The antioxidant activities were strongly influenced by the length of the polyene chain and the type of terminal function as well. Considering our results and the low amounts of apo-lycopenals found in plasma as well as in lycopene-rich food products compared to (all-E)-lycopene we speculate that the effects of apo-lycopenoids as direct antioxidants in food samples as well as in blood and/or target tissues can be stated as negligible. Apo-lycopenoids may act as indirect antioxidants by activation of gene expression of antioxidant-derived enzymes.     

Effects of β-carotene and lycopene thermal degradation products on the oxidative stability of soybean oil

The relative oxidative stability of soybean oil samples containing either thermally degraded β-carotene or lycopene was determined by measuring peroxide value (PV) and headspace oxygen depletion (HOD) every 4 h for 24 h. Sobyean oil samples containing 50 ppm degraded β-carotene that were stored in the dark at 60°C displayed significantly (P<0.01) higher HOD values compared with controls. Lycopene degradation products (50 ppm) in soybean oil significantly (P<0.05) decreased HOD of samples when stored in the dark. PV and HOD values for samples containing 50 ppm of either β-carotene or lycopene degradation products stored under lighted conditions did not differ significantly from controls (P<0.05). However, soybean oil samples containing 50 ppm of unheated, all-trans β-carotene or lycopene stored under light showed significantly lower PV and HOD values than controls (P<0.01). These results indicated that during autoxidation of soybean oil held in the dark, β-carotene thermal degradation products acted as a prooxidant, while thermally degraded lycopene displayed antioxidant activity in similar soybean oil systems. In addition, β-carotene and lycopene degradation products exposed to singlet oxygen oxidation under light did not increase or decrease the oxidative stability of their respective soybean oil samples.     

Suppression by carotenoids of microtenoids of microcystin-induced morphological changes in mouse hepatocytes

Microcystin-LR is a liver tumor promoter in the okadaic acid class, a group of potent inhibitors of protein phosphatases 1 and 2A. Because of inhibition of protein phosphatases, microcystin-LR induces hyperphosphorylation of cellular proteins, including cytoskeletal proteins—cytokeratins 8 and 18—and causes morphological changes in mouse hepatocytes in primary culture. We studied the effects of carotenoids to antagonize microcystin-LR-induced morphological changes in hepatocytes. β-Carotene (100 nM to 100 μM), suppressed the morphological changes induced by 100 nM microcystin-LR in a dose-dependent manner. Other carotenoids tested exerted similar suppressive effects, although retinoids, such as all-trans retinol, all-trans retinoic acid, and 9-cis retinoic acid, were only weakly suppressive. The relative potency of the suppression correlated significantly with the number of conjugated double bonds in thetrans configuration. β-Carotene strongly suppressed the hyperphosphorylation of cellular proteins induced by microcystin-LR without significant changes in the basal phosphorylation level. Other antioxidants, such as α-tocopherol, did not protect the cells against microcystin-LR. Taken together, the antagonistic effects of carotenoids against microcystin-LR are difficult to explain by their antioxidant or provitamin A activities. Suppression of the hyperphosphorylation of cellular proteins may be a novel mechanism by which carotenoids inhibit tumor promotion.     

Kinetics of all-trans-β-carotene degradation on heating with and without phenylalanine

All-trans-β-carotene was heated in liquid paraffin at 210°C for 15 min in the presence and the absence of phenylalanine to assess the effect of the amino acid on the rate of degradation of all-trans-β-carotene. The curve that represents all-trans-β-carotene degradation in both model systems is formed of two distinct parts that correspond, respectively, to the propagation and termination phases of an autocatalytic reaction. The reaction over 1–15 min followed first-order reaction kinetics in both systems, and the rate constant obtained was 2.8 times lower in the presence of phenylalanine. The kinetic behavior and the rate constant for color loss were similar to those for all-trans-β-carotene degradation for each model system.     

The effect of copper,managanese and cobalt acetates on the autoxidation oftrans-9,trans-11-octadecadienoic acid in 90% v/v aqueous acetic acid

The autoxidation oftrans-9,trans-11-octadecadienoic acid in 90% v/v aqueous acetic acid has been studied, at 80 C, with and without copper, manganese and cobalt acetate. The initial 9,11-octadecadienoic acid concentration was 0.05 M in most of the experiments. The metallic acetate concentrations were 10⁻⁵ to 10⁻² M. Copper and manganese acetates retard the autoxidation. With copper acetate, this retardation involves both the induction period and the rapid autocatalytic stage. Manganese acetate prolongs the induction period. A slightly lowered rate is observed at low cobalt acetate concentrations (∼10⁻⁵ M), but higher cobalt acetate concentrations clearly accelerate the autoxidation.     

Autoxidation of linoleic acid and behavior of its hydroperoxides with and without tocopherols

The autoxidation of linoleic acid dispersed in an aqueous media and the effect of α-, γ- and δ-tocopherols were studied. The quantitative analysis of the hydroperoxide isomers (13-cis,trans; 13-trans,trans; 9-trans,cis; 9-trans,trans) by direct high-performance liquid chromatography exhibited a prooxidant activity of α-tocopherol at high concentration (3.8% by weight of linoleic acid). On the other hand, α-tocopherol at lower concentrations (0.38 and 0.038%) and γ- and δ-tocopherols at high concentration (3.8%) were antioxidant. Furthermore, the addition of tocopherols modified the distribution of the geometrical isomers. The formation of thetrans,trans hydroperoxide isomers was completely inhibited by the highest concentration of the three tocopherols independently of their antioxidant or prooxidant activity and only delayed by the lower concentrations of α-tocopherol. The addition of tocopherols to hydroperoxide isomers reduced the decomposition rate of these isomers in the order α-tocopherol < γ-tocopherol < δ-tocopherol for thecis,trans hydroperoxide isomer and α-tocopherol ≪ γ-tocopherol ⋍ δ-tocopherol for thetrans,trans hydroperoxide isomer. With these hydroperoxides, as during linoleic acid autoxidation, α-tocopherol was completely oxidized whatever its initial concentration, while γ-tocopherol underwent partial oxidation and δ-tocopherol was practically unchanged.     

Oxidation and isomerization of retinoic acid by iodine and light: A novel preparation of all-trans- and 13-cis-4-oxoretinoic acid

A mixture of all-trans-retinoic acid and iodine in heptane was irradiated. Two oxidation products were isolated by high performance liquid chromatography and identified as all-trans- and 13-cis-4-oxoretinoic acid by nuclear magnetic reasonance, ultra violet, Infrared spectroscopy, and mass spectral analysis. Under the same conditions, but without light, a mixture of all-trans- and 13-cis-retinoic acid resulted. The corresponding methyl esters were obtained when methyl all-trans-retinoate was used in place of all-trans-retinoic acid.     

Effects of dietary 9-trans, 12-trans linoleate on arachidonic acid metabolism in rat platelets

In order to determine the minimal amount of dietary 9-trans,12-trans-linoleate which can decrease endoperoxide metabolites synthesized and their precursor in rat platelets, graded amounts (0, 0.1, 0.5, 1.0, 2.5%) of thetrans-linoleate were fed to rats with a constant amount of all-cis-linoleate (2.5%) for 12 weeks. Arachidonic acid levels in platelet phospholipids of groups receiving thetrans-linoleate at 2.5 and 1.0% were significantly (p<0.01) lower than that of the control receiving notrans-linoleate. Concentrations of TXB₂ and PGF_2α in sera of the group receiving 2.5%trans-linoleate were significantly (p<0.05) lower than those of the control; however, there was no difference between the group receiving 1.0%trans-linoleate and the control. To determine whether the difference in serum concentrations of endoperoxide metabolites could be manifested if rats were fed for longer period of time, 2 groups of rats were again fed diets containing 0 and 1.0%trans-linoleate, respectively, for 16 weeks. Arachidonic acid in platelet phospholipids of the group receiving thetrans-linoleate was again significantly (p<0.01) lower than that of the control group. Concentrations of TXB₂ and PGF_2α, and 12-hydroxyeicosatetraenoic acid formed in platelets, were smaller in the group receivingtrans-linoleate than the control group; however, the difference was not statistically significant. These results indicated that all-trans-linoleate can reduce arachidonic acid metabolites formed in rat platelets when its dietary level is equal to or exceeds the level of all-cis-linoeate.     

Oxidative degradation kinetics of lycopene, lutein, and 9-cis and all-trans β-carotene

The thermal and oxidative degradation of carotenoids was studied in an oil model system to determine their relative stabilities and the major β-carotene isomers formed during the reaction. All-trans β-carotene, 9-cis β-carotene, lycopene, and lutein were heated in safflower seed oil at 75, 85, and 95°C for 24, 12, and 5 h, respectively. The major isomers formed during heating of β-carotene were 13-cis, 9-cis, and an unidentified cis isomer. The degradation kinetics for the carotenoids followed a first-order kinetic model. The rates of degradation were as follows: lycopene>all-trans β-carotene≈9-cis β-carotene>lutein. The values for the thermodynamic parameters indicate that a kinetic compensation effect exists between all of the carotenoids. These data suggest that lycopene was most susceptible to degradation and lutein had the greatest stability in the model system of the carotenoids tested. Furthermore, there was no significant difference in the rates of degradation for 9-cis and all-trans β-carotene under the experimental conditions.     

Synthesis of sulfur-Containing derivatives from olefinic fatty esters

The reaction of 3-mercaptopropan-l,2-diol with methyl 10-undecenoate (Ib) yielded three products, methyl 11-(3′-mercaptopropan-l′,2′-diacetoxy) undecanoate (II, 48.9%), methyl 11-(1-oxapropan-2′-acetoxy-3′-mercaptoacetyl) undecanoate (III, 27.4%) and methyl 10-(3′-mercaptopropan-1′-acetoxy-2′-ol) undecanoate (IV, 23.0%) along with hydrolyzed starting material (Ia, 5.4%). The same reaction with methyl 9-octadecenoate (Vb) gave an isomeric product, 9(10)-(3′-mercaptopropan-l′-acetoxy-2′-ol) octadecanoic acid (VI, 78.5%) and oleic acid (Va, 21.4%). Reaction withtrans-2-octadecenoic acid (VII) afforded 2(3)-(3′-mercaptopropan-l′-acetoxy-2′-ol) octadecanoic acid (VIII, 85.7%).     

Preparation and fractionation of conjugated trienes from α-linolenic acid and their growth-inhibitory effects on human tumor cells and fibroblasts

Conjugated α-linolenic acid (ClnA) was prepared from α-linolenic acid (9,12,15–18∶3n−3, LnA) by alkaline treatment; we fractionated CLnA into three peaks by reversed-phase column-HPLC as evidenced by monitoring absorbance at 205, 235, and 268 nm. Peak I was a conjugated dienoic FA derived from LnA, whereas Peaks II and III were conjugated trienoic LnA. Proton NMR analysis showed that Peak III consisted of the all-trans isomer. The methylated Peak III was further divided into five peaks (Peaks IV–VIII) by silver ion column-HPLC. Peak V, a major constituent in the Peak III fraction, was identified as conjugated 10t,12t,14t-LnA by GC-EIMS and ¹H NMR analysis. Peaks III and V, which consisted of conjugated all-trans trienoic LnA, had stronger growth-inhibitory effects on human tumor cell lines than the other collected peaks and strongly induced lipid peroxidation as compared with Peaks I, II, and LnA. We propose that conjugated all-trans trienoic FA have the strongest growth-inhibitory effect among the conjugated trienoic acids and conjugated dienoic acids produced by alkaline treatment of α-LnA, and that this effect is mediated by lipid peroxidation.     

Protective effect of phytic acid hydrolysis products on iron-induced lipid peroxidation of liposomal membranes

Beneficial effects of dietary phytic acid (myo-inositol hexaphosphate; IP₆) have often been explained by its strong iron ion-chelating ability, which possibly suppresses iron ion-induced oxidative damage in the gastrointestinal tract. Because phytic acid is hydrolyzed during digestion, this work aimed to know whether its hydrolysis products (IP_2′ IP_3′, IP_4′ and IP₅) could still prevent iron ion-induced lipid peroxidation. Studies using liposomal membranes demonstrated that hydrolysis products containing three or more phosphate groups are able to inhibit iron ion-induced lipid peroxidation although their effectiveness decreased with dephosphorylation. Similarly, they also prevented iron ion-induced decomposition of phosphatidylcholine hydroperoxide. These results demonstrate that intermediate products of phytic acid hydrolysis still possess iron ion-chelating ability, and thus they can probably prevent iron ion-induced lipid peroxidation in biological systems.     

The inhibition of autoxidation by aromatic amines

Recent work on the inhibition of autoxidation by aromatic amines is reviewed. The rate controlling step for the inhibition process is abstraction of the amino hydrogen by a peroxy radical. The rate of this reaction is increased by electron donating substituents attached to the aromatic ring. Nitroxide radicals may be produced in the reaction of peroxy radicals with secondary amino radicals. The efficiency of nitroxide formation is greater for tertiary than for secondary peroxy radicals because, in the latter case, the caged nitroxide and alkoxy radical may disproportionate to give a hydroxylamine and a carbonyl compound. Primary aromatic amines do not give nitroxides, presumably because the peroxy radical-amino radical reaction gives an alcohol and a nitroso aromatic. The tertiary amine, N,N,N′,N′-tetramethyl-p-phenylenediamine is shown to be a catalyst of autoxidation rather than an inhibitor, as has been previously reported. The products of the N-phenyl-2-naphthylamine-peroxy radical reaction have been identified. Presented at the AOCS Meeting, San Francisco, April 1969.     

Prooxidant effects of inorganic chromium compounds in the autoxidation of methyl linoleate

The prooxidant property of inorganic chromium compounds was determined in methyl linoleate free from natural antioxidants and metals. Prooxidant properties of inorganic chromium compounds appeared in order of sodium chromate > chromium (VI)-oxide > chromium chloride > potassium chromate > chromium (III)-oxide > potassium dichomate. In comparison with the control, additions of chromium compounds induced different amounts of autoxidation products derived from methyl linoleate, such as small amounts of hydroperoxides and conjugated dienes and large amounts of hydroxy groups,α,β,γ,δ-unsaturated carbonyls, isolatedtrans double bonds, polymers, and free radicals. From these analytical data, the catalysis of chromium compounds in the autoxidation of methyl linoleate seemed to be based on their abilities of abstracting a hydrogen from methyl linoleate and decomposing hydroperoxides derived from the autoxidation of methyl linoleate.     

Synthesis of substituted fatty oxathiolanes and thioethers from an allylic oxo fatty acid ester

Substituted oxathiolane and thioether derivatives have been synthesized from an allylic oxo fatty acid ester. The reaction of methyl 4-oxo-trans-2-octadecenoate with 3-mercaptopropan-1,2-diol (1-thioglycerol) affords methyl 4-(3′-hydroxymethyl-1′,4′-oxathiolane)-2(3)-(O-mercaptopropan-1″,2″-diol)-octadecanoate (II), methyl 4-oxo-2(3)-(O-mercaptopropan-1′,2′-diol)-octadecanoate (III), methyl 4-(3′-hydroxy-l′,5′-oxathiane)-2 (3)-(S-mercaptopropan-1″,2″-diol)-octadecanoate (IV), methyl 4-oxo-2(3)-(S-mercaptopropan-1′, 2′diol)-octadecanoate (V) and methyl 4-(3′-hydroxymethyl-1′, 4′-oxathiolane)-2(3)-(S-mercaptopropan-1″, 2″-diol)-octadecanoate (VI). Structures of the individual reaction products have been established on the basis of spectral data and microanalyses.     

A comparison of lycopene and astaxanthin absorption from corn oil and olive oil emulsions

The effect of different oils on the absorption of carotenoids was investigated in mesenteric lymph duct cannulated rats. Sixteen treatment emulsions containing increasing concentrations of either lycopene (LYC) or astaxanthin (AST) (5, 10, 15, 20 μmol/L) were prepared with olive oil or corn oil and continuously infused into the duodenum of the rat. Absorption of carotenoids into the mesenteric lymph duct was determined. Absorption of LYC and AST from both oils increased with the amount infused into the duodenum. The average recovery of AST in the lymph from the olive oil emulsion was 20% but was decreased to 13% from emulsions containing corn oil. Lycopene was not as well absorbed as AST. The average recovery of LYC was 6% from olive oil emulsions but only 2.5% when infused with corn oil. The LYC used in this study was isolated from tomato paste and was primarily in the all-trans form. We did not observe any significant isomerization of all-trans LYC to 9-cis LYC during absorption. We conclude that the type of oil with which a carotenoid is consumed can influence its absorption.     

Peroxyl and hydroxyl radical scavenging activity of some natural phenolic antioxidants

The autoxidation of linoleic acid dispersed in an aqueous media and the antioxidant effect of hydroxytyrosol, oleuropein, caffeic acid and tyrosol were studied. Linoleic acid autoxidation rate was estimated by the increase of conjugated diene level and by the decrease of linoleic acid content in the samples. The phenolic compounds exhibited an antioxidant activity which increased in the order: tyrosol < caffeic acid < oleuropein < hydroxytyrosol. The analysis of the hydroperoxide isomers pointed out that hydroxytyrosol, oleuropein and caffeic acid at a concentration of 10⁻⁴M inhibited the formation oftrans- trans isomers in the increasing order: caffeic acid < oleuropein < hydroxytyrosol. This inhibition could be related to the ability of phenolic compounds to scavenge peroxyl radical. Tyrosol did not inhibit the formation oftranstrans isomers. Phenolic compounds were degraded as a consequence of their antioxidant activity and their degradation rate was positively correlated to their antioxidant efficacy. These phenolic compounds, at a concentration of 6 × 10⁻³M, also scavenged hydroxyl radical, with an efficiency which increased in the order: tyrosol < hydroxytyrosol < oleuropein < caffeic acid. Polar substituents at the para position, such as in caffeic acid and oleuropein, were correlated with higher hydroxyl radical quenching ability.     

Reactions of fatty materials with oxygen. XX. Recent developments in the autoxidation of methyl oleate and other monounsaturated fatty materials

Summary Some significant developments since 1947 in the autoxidation of methyl oleate and other monounsaturated fatty materials have been reviewed and critically evaluated. Subjects discussed are preparation and characterization of hydroperoxides, and mechanism, kinetics, and secondary products of autoxidation. Major developments in the field have resulted largely from the use of newer instruments (polarograph, infrared spectrophotometer) and separation techniques (urea complexes, molecular distillation, countercurrent distribution). Direct experimental evidence is now available which demonstrates that a) hydroperoxides are the predominating, but not the exclusive, primary products of autoxidation; b) the hydroperoxides obtained from methyl oleate are mostly, if not entirely,trans; c) substantially all the methyl oleate undergoes single attack in the chain before any significant amount of multiple attack occurs, and d) α,β-unsaturated carbonyl compounds are among the most important secondary products of autoxidation. Paper XIX is reference 66a. Presented at the Fall Meeting of the American Oil Chemists' Society, Philadelphia, Pa., October 10–12, 1955. A laboratory of the Eastern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Solubility in supercritical carbon dioxide of the predominant carotenes of tomato skin

Solubilities in supercritical carbon dioxide of the predominant carotenes in tomato skin were measured. The use of a polymeric C₃₀ RP-HPLC column to analyze the tomato extract made it possible to separate several geometric isomers from each carotene extracted. The Chrastil model was used to assign a solubility equation to each extracted carotene. Different solubility behaviors in supercritical carbon dioxide were shown by carotenes depending on their nature and configuration. The most soluble carotene was all-trans-phytoene and the least soluble was all-trans-lycopene. Significant differences in solubility were observed between the trans and cis isomers of lycopene. The results indicate that a fractionation of the tomato skin carotenes can be achieved by using supercritical CO₂ extraction.     

Lack of regioselectivity in formation of oxohydroxyoctadecenoic acids from the 9- or 13-hydroperoxide of linoleic acid

Either 9-hydroperoxy-trans-10,cis-12-octadecadienoic acid or 13-hydroperoxy-cis-9,trans-11-octadecadienoic acid was treated with the catalyst, cysteine-FeCl₃, in the presence of oxygen. Oxohydroxyoctadecenoic acids were among the many products formed as a result of hydroperoxide decomposition. A mixture of 9(13)-oxo-13(9)-hydroxy-trans-11(10)-octadecenoic acids (δ-ketols) was produced from either isomeric hydroperoxide. The formation of isomeric δ-ketols from 9-hydroxy-trans-12,13-epoxy-trans-10-octadecenoic acid (epoxyol), a known product of 13-hydroperoxy-cis-9,trans-11-octadecadienoic acid decomposition, implies that the epoxyol is an intermediate. The mechanism was elucidated by the facile conversion of the epoxyol (methyl ester_ to methyl 9(13)-oxo-13(9)-hydroxy-trans-11(10)-octadecenoates with a Lewis acid, BF₃-etherate. Presented at the 14th World Congress, International Society for Fat Research, Brighton, U.K., September 17–22, 1978. The mention of firm names or trade products does not imply that they are endorsed or recomended by the U.S. Department of Agriculture over other firms or similar products not mentioned.