Alejandro Betancor-Fernandez

Heinrich-Heine-Universität Düsseldorf, Düsseldorf, North Rhine-Westphalia, Germany

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Publications (4)5.31 Total impact

  • Alejandro Betancor-Fernández, Antonio Pérez-Gálvez, Helmut Sies, Wilhelm Stahl
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    ABSTRACT: Pharmaceutical preparations derived from natural sources such as vegetables often contain compounds that contribute to the antioxidant defence system and apparently play a role in the protection against degenerative diseases. In the present study, commercial preparations containing extracts of turmeric, artichoke, devil's claw and garlic or salmon oil were investigated. The products were divided into fractions of different polarity, and their antioxidant activity was determined using the Trolox equivalent antioxidant capacity (TEAC) assay. This test is based on the efficacy of the test material to scavenge 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) derived radicals. Total phenols were determined in all fractions as well as specific carotenoids in the most lipophilic fraction to assess their contribution to the antioxidant activity. For comparison, the radical scavenging effect of selected constituents of the extracts such as curcumin, luteolin, kaempferol, chlorogenic acid, harpagoside, beta-carotene and alpha-tocopherol was investigated and compared with that of Trolox. Curcumin, luteolin, kaempferol, chlorogenic acid and beta-carotene showed an antioxidant activity superior to Trolox in the TEAC assay; harpagoside was barely active. All fractions of the turmeric extract preparation exhibited pronounced antioxidant activity, which was assigned to the presence of curcumin and other polyphenols. The antioxidant activity corresponding to the artichoke leaf extract was higher in the aqueous fractions than in the lipophilic fractions. Similarly, devil's claw extract was particularly rich in water-soluble antioxidants. Harpagoside, a major compound in devil's claw, did not contribute significantly to its antioxidant activity. The antioxidant capacity of the garlic preparation was poor in the TEAC assay. That of salmon oil was mainly attributed to vitamin E, which is added to the product for stabilization. In all test preparations, the antioxidant activity was significantly correlated with the content of total phenolic compounds.
    Journal of Pharmacy and Pharmacology 08/2003; 55(7):981-6. · 2.03 Impact Factor
  • Alejandro Betancor-Fernandez, Helmut Sies, Wilhelm Stahl, M Cristina Polidori
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    ABSTRACT: 2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC) has been identified as a major water-soluble metabolite of vitamin E, which circulates in the blood and is excreted with the urine. The aim of this study was to assess the antioxidant activity of alpha-CEHC using several methods with different prooxidant challenges. In the Oxygen Radical Absorbance Capacity assay, a fluorescent protein acts as a marker for oxidative damage induced by peroxyl radicals. In the Trolox Equivalent Antioxidant Capacity (TEAC) assay, a stable free radical, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS.+) is reduced directly by antioxidants. Scavenging properties vs. reactive nitrogen species were studied measuring the effects on tyrosine nitration after reaction with peroxynitrite. Trolox, alpha-tocopherol, ascorbic acid, and (-)-epicatechin were simultaneously tested in order to compare their antioxidant activities. In all mentioned systems, alpha-CEHC exhibited antioxidant properties similar to those of Trolox. We conclude that alpha-CEHC is a molecule with good antioxidant activity, having the advantage over Trolox of being a naturally occurring compound. These properties might be useful for research or industrial purposes.
    Free Radical Research 09/2002; 36(8):915-21. · 3.28 Impact Factor
  • Alejandro Betancor-Fernandez, Helmut Sies, Wilhelm Stahl, M. Cristina Polidori
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    ABSTRACT: 2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman ( f -CEHC) has been identified as a major water-soluble metabolite of vitamin E, which circulates in the blood and is excreted with the urine. The aim of this study was to assess the antioxidant activity of f -CEHC using several methods with different prooxidant challenges. In the Oxygen Radical Absorbance Capacity assay, a fluorescent protein acts as a marker for oxidative damage induced by peroxyl radicals. In the Trolox Equivalent Antioxidant Capacity (TEAC) assay, a stable free radical, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS ” + ) is reduced directly by antioxidants. Scavenging properties vs. reactive nitrogen species were studied measuring the effects on tyrosine nitration after reaction with peroxynitrite. Trolox, f -tocopherol, ascorbic acid, and ( m )-epicatechin were simultaneously tested in order to compare their antioxidant activities. In all mentioned systems, f -CEHC exhibited antioxidant properties similar to those of Trolox. We conclude that f -CEHC is a molecule with good antioxidant activity, having the advantage over Trolox of being a naturally occurring compound. These properties might be useful for research or industrial purposes.
    Free Radical Research - FREE RADICAL RES. 01/2002; 36(8):915-921.
  • Source
    Alejandro José Betancor-Fernández
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    ABSTRACT: In der vorliegenden Arbeit wurden antioxidative Eigenschaften wichtiger Mikronährstoffe (Vitamin E, Vitamin E Derivate, Carotinoide und Polyphenole) untersucht. Die Versuche fanden auf drei Ebenen statt: 1. In einer Serie zellfreier Systeme. U.a. wurde der Trolox Equivalent Antioxidant Capacity (TEAC)- Wert für alle Verbindungen und für rationale Phytopharmaka aus Curcumawurzelstock, Teufelskrallenwurzel, Artischokenblättern und Knoblauch, sowie für ein Lachsölpräparat ermittelt. 2. Unter pro-atherogenen Bedingungen auf Zellebene. Dafür wurden primäre Mausaortaendothelzellen (MAEC) mit oxidiertem LDL inkubiert. Die Auswirkung einer Vorbehandlung mit ausgewählten Mikronährstoffen bzw. 2,5,7,8-Tetramethyl-2(2´-carboxyethyl)-6-hydroxychroman (alpha-CEHC, einem alpha-Tocopherol Metabolit) wurde auf Indikatoren der Zellviabilität, des Redoxstatus, der oxLDL- Aufnahme und der Apoptose hin untersucht. 3. In einer Interventionsstudie am Menschen. Rauchen führt zur Induktion von Fremdstoffwechselenzymen (z. B. Cytochrom P450- abhängigen Monoxygenasen) und erhöht den oxidativen Stress. Beide Faktoren können somit den Blutspiegel bestimmter Antioxidanten ändern und deren Stoffwechsel beeinflussen. 29 Rauchern und Nichtrauchern wurde eine p. o. Dosis von Vitamin E verabreicht. Bei beiden Gruppen wurden über 72 h hinweg der Serumspiegel des alpha- und gamma-Tocopherol sowie die Serumkonzentrationen von deren Abbauprodukten alpha- und gamma-CEHC beobachtet. Zu 1: In den sogenannten Total Antioxidant Capacity Tests waren nahezu alle Mikronährstoffe sowie das Vitamin E- Metabolit aktiv. Die Ergebnisse des Trolox Equivalent Antioxidant Capacity (TEAC) Versuchs, welcher auf einer Reduktion des ABTS Radikals basiert, konnten durch die strukturellen Eigenschaften aller untersuchten Verbindungen erläutert werden; wichtige Faktoren bei Carotinoiden waren molekulare Symmetrie, Verteilung der Doppelbindungen sowie Substitutionen der terminalen Ringe mit Hydroxylgruppen; die Länge der Seitenkette zeigte keinen Einfluss auf die antioxidative Aktivität von alpha-Tocopherol, seinem Strukturanalogon Trolox oder alpha-CEHC. Der Curcumaextrakt war reich an lipophilen und hydrophilen Antioxidanten. Die antioxidativen Kapazitäten der Artischoken- und Teufellskrallenextrakte waren beträchtlich geringer und korrelierten in signifikanter Weise mit deren Polyphenolinhalt. Der Knoblauchextrakt und das Lachsöl waren nahezu inaktiv. Zu 2: Alpha-Tocopherol und die Catechine schwächten die durch oxLDL verursachte Zellschädigung über 24 h hinweg ab. Einige beteiligte Mechanismen waren: Das Abfangen von ROS, die Erhaltung des Glutathions- und Thiolpools der Zelle und die Caspase-3- Hemmung bzw. Represion. Zu 3: Bei Rauchern war zu jedem Zeitpunkt der gamma-CEHC Spiegel signifikant und der alpha-CEHC Spiegel nicht signifikant höher als bei Nichtrauchern. Dieser Effekt war von der Supplementierung mit alpha-Tocopherol unabhängig. Da gamma-Tocopherol bekanntlich zügiger als alpha-Tocopherol metabolisiert wird, wird hierbei vorgeschlagen, dass die Biotransformation bei Rauchern durch eine Induktion Vitamin E- abbauender Enzyme unterstützt wird. The antioxidant properties of selected micronutrients (vitamin E, vitamin E derivatives, carotenoids, and polyphenolic compounds) were assessed. Studies were performed at three different experimental levels: (1) In cell-free model systems. The Trolox Equivalent Antioxidant Capacity (TEAC) was measured for all compounds and for pharmaceutical preparations with a broad range of therapeutic indications (derived from turmeric rhizome, devil´s claw root, artichoke leaf, garlic, and salmon oil); for selected compounds both the Oxygen Radical Absorbance Capacity (ORAC) and the half-maximal inhibitory concentration IC(50) against peroxynitrite-mediated nitration of tyrosine were determined. (2) At cellular level, under pro-atherogenic conditions. Primary mouse aorta endothelial cells were incubated with oxidatively-modified low density lipoproteins (oxLDL) in different time frames. The effects of pre-treating cells with selected dietary micronutrients or 2,5,7,8-tetramethyl-2(2´-carboxyethyl)-6-hydroxychroman (alpha-CEHC) on indicators of cell viability, redox state, amount of oxLDL uptake, and apoptosis were investigated. (3) In a human intervention trial. In smokers, oxidative stress is increased and xenobiotic-detoxicating enzymes, e. g. cytochrome P450-dependent monoxygenases, are induced. Both factors may modify the levels of certain antioxidants in blood and affect their metabolism. 29 smoking and nonsmoking volunteers received a single oral dose of vitamin E. Both the serum levels of alpha- and gamma-tocopherol and their major metabolites (alpha- and gamma-CEHC) were monitored for 72 h and both groups were compared. RESULTS. To (1): Most of the test micronutrients and alpha-CEHC exhibited antioxidant activities in the TEAC and ORAC assays. The differences in activity observed in the TEAC assay were assigned to particular structural features of each compound: in flavonoids, the number of neighbouring hydroxyl groups on ring B was most important; in carotenoids, molecular symmetry, the position of double bonds and absence/presence of hydroxyl groups in the terminal rings were the most decisive factors; the length of the side chain had no influence on the antioxidant activity of alpha-tocopherol, its structural analogue Trolox, and alpha-CEHC. The turmeric extract was rich in lipophilic and hydrophilic antioxidants. The antioxidant capacity of artichoke and devil´s claw extracts was considerably lower and was significantly correlated with the polyphenol content. Garlic and salmon oil preparations were almost inactive in the TEAC assay. To (2): alpha-Tocopherol and catechin compounds counteracted oxLDL-induced cell damage to some extent over a period of 24 h. Involved mechanisms comprised ROS scavenging, maintenance of glutathione and the total thiol redox status, and inhibition/repression of caspase-3. To (3): In smokers, overall levels of the gamma-tocopherol metabolite gamma-CEHC were significantly higher and those of alpha-CEHC non-significantly higher than in nonsmokers, even though this effect appeared to be independent of alpha-tocopherol supplementation. Since gamma-tocopherol is preferentially metabolized compared to alpha-tocopherol, it may be speculated that biotransformation is enhanced in smokers due to induction of vitamin E degrading enzymes, e. g. cytochrome P450-dependent monoxygenases.

Publication Stats

43 Citations
5.31 Total Impact Points

Institutions

  • 2002–2003
    • Heinrich-Heine-Universität Düsseldorf
      • • Institut für Biochemie und Molekularbiologie I
      • • Institut für Physikalische Chemie
      Düsseldorf, North Rhine-Westphalia, Germany