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  1. Article ; Online: Determination of antiradical and antioxidant activity: basic principles and new insights.

    Tirzitis, Gunars / Bartosz, Grzegorz

    Acta biochimica Polonica

    2010  Volume 57, Issue 2, Page(s) 139–142

    Abstract: Although the term 'antioxidant' is used very frequently, there are problems with the definition of antioxidants and estimation of antioxidant activity. The distinction between antioxidant and antiradical activities is not always obvious. This minireview ... ...

    Abstract Although the term 'antioxidant' is used very frequently, there are problems with the definition of antioxidants and estimation of antioxidant activity. The distinction between antioxidant and antiradical activities is not always obvious. This minireview discusses critically the principles, advantages and limitations of the most frequently used methods of estimation of antiradical and antioxidant activities.
    MeSH term(s) Animals ; Antioxidants/pharmacology ; Biphenyl Compounds/pharmacology ; Humans ; Hydroxyl Radical/pharmacology ; Molecular Structure ; Oxidation-Reduction/drug effects ; Picrates/pharmacology ; Reactive Oxygen Species/metabolism
    Chemical Substances Antioxidants ; Biphenyl Compounds ; Picrates ; Reactive Oxygen Species ; Hydroxyl Radical (3352-57-6) ; 1,1-diphenyl-2-picrylhydrazyl (DFD3H4VGDH)
    Language English
    Publishing date 2010
    Publishing country Poland
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 595762-x
    ISSN 1734-154X ; 0001-527X
    ISSN (online) 1734-154X
    ISSN 0001-527X
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Betulin binds to melanocortin receptors and antagonizes alpha-melanocyte stimulating hormone induced cAMP generation in mouse melanoma cells.

    Muceniece, Ruta / Saleniece, Kristine / Riekstina, Una / Krigere, Liga / Tirzitis, Gunars / Ancans, Janis

    Cell biochemistry and function

    2007  Volume 25, Issue 5, Page(s) 591–596

    Abstract: Betulin is a principal component of birch bark and is known to possess a broad range of biological activities, including antiinflammatory, antiviral and anticancer actions. The present study was carried out in vitro to clarify the influence of betulin on ...

    Abstract Betulin is a principal component of birch bark and is known to possess a broad range of biological activities, including antiinflammatory, antiviral and anticancer actions. The present study was carried out in vitro to clarify the influence of betulin on melanocortin (MC) receptor-ergic signalling by using COS-7 cells transfected with corresponding human MC receptor DNA. The results showed that betulin binds to the human melanocortin MC1, three to five receptors with selectivity to the MC1 subtype (K(i) value 1.022 +/- 0.115 microM). Betulin binds to the MC receptors with the following potency order-MC > MC3 > MC5 > MC4. Betulin itself does not stimulate cAMP generation, however, it slightly antagonizes alpha-melanocyte-stimulating hormone (alpha-MSH)-induced cAMP accumulation in the mouse melanoma cell line B16-F1. As a water-insoluble substance, betulin was dissolved in DMSO therefore DMSO competition with the labelled ligand NDP-MSH for the binding to the MC receptors was tested in the identical experimental set-up. We found that DMSO competes for binding to all the MC receptor subtypes, at 20% concentration and above. Selectivity for one or another receptor subtype was not observed. We have demonstrated for the first time, the ability of the plant compound betulin to bind to the MC receptors. One may suggest MC receptor MC1 subtype as the essential target for the antimelanoma action of betulin and its structurally close molecules such as betulinic acid. Moreover, we have found a new non-peptide small molecule MC mimetic, that is betulin. Thus, we report a new chemical motif for the binding to the MC receptors that could be used as a template for the search of more selective MC mimetics.
    MeSH term(s) Animals ; Binding, Competitive/drug effects ; COS Cells ; Cercopithecus aethiops ; Cyclic AMP/metabolism ; Humans ; Kinetics ; Melanoma/pathology ; Mice ; Receptors, Melanocortin/metabolism ; Triterpenes/metabolism ; alpha-MSH/analogs & derivatives ; alpha-MSH/pharmacology
    Chemical Substances Receptors, Melanocortin ; Triterpenes ; alpha-MSH (581-05-5) ; betulin (6W70HN7X7O) ; MSH, 4-Nle-7-Phe-alpha- (75921-69-6) ; Cyclic AMP (E0399OZS9N)
    Language English
    Publishing date 2007-09
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 283643-9
    ISSN 1099-0844 ; 0263-6484
    ISSN (online) 1099-0844
    ISSN 0263-6484
    DOI 10.1002/cbf.1427
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Natural and synthetic antioxidants: an updated overview.

    Augustyniak, Agnieszka / Bartosz, Grzegorz / Cipak, Ana / Duburs, Gunars / Horáková, L'ubica / Luczaj, Wojciech / Majekova, Magdalena / Odysseos, Andreani D / Rackova, Lucia / Skrzydlewska, Elzbieta / Stefek, Milan / Strosová, Miriam / Tirzitis, Gunars / Venskutonis, Petras Rimantas / Viskupicova, Jana / Vraka, Panagiota S / Zarković, Neven

    Free radical research

    2010  Volume 44, Issue 10, Page(s) 1216–1262

    Abstract: Abstract The current understanding of the complex role of ROS in the organism and pathological sequelae of oxidative stress points to the necessity of comprehensive studies of antioxidant reactivities and interactions with cellular constituents. Studies ... ...

    Abstract Abstract The current understanding of the complex role of ROS in the organism and pathological sequelae of oxidative stress points to the necessity of comprehensive studies of antioxidant reactivities and interactions with cellular constituents. Studies of antioxidants performed within the COST B-35 action has concerned the search for new natural antioxidants, synthesis of new antioxidant compounds and evaluation and elucidation of mechanisms of action of both natural and synthetic antioxidants. Representative studies presented in the review concern antioxidant properties of various kinds of tea, the search for new antioxidants of herbal origin, modification of tocopherols and their use in combination with selenium and properties of two promising groups of synthetic antioxidants: derivatives of stobadine and derivatives of 1,4-dihydropyridine.
    MeSH term(s) Animals ; Antioxidants/chemical synthesis ; Antioxidants/pharmacology ; Carbolines/chemistry ; Carbolines/pharmacology ; Dihydropyridines/chemistry ; Dihydropyridines/pharmacology ; Humans ; Oxidative Stress/drug effects ; Plant Preparations/chemistry ; Plant Preparations/pharmacology ; Selenium Compounds/chemistry ; Selenium Compounds/pharmacology ; Tea/chemistry ; Tocopherols/chemistry ; Tocopherols/pharmacology
    Chemical Substances Antioxidants ; Carbolines ; Dihydropyridines ; Plant Preparations ; Selenium Compounds ; Tea ; 1,4-dihydropyridine (7M8K3P6I89) ; Tocopherols (R0ZB2556P8) ; dicarbine (Y0EA50IJ3V)
    Language English
    Publishing date 2010-10
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 1194130-3
    ISSN 1029-2470 ; 1071-5762
    ISSN (online) 1029-2470
    ISSN 1071-5762
    DOI 10.3109/10715762.2010.508495
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Bioactive 1,4-dihydroisonicotinic acid derivatives prevent oxidative damage of liver cells.

    Borovic, Suzana / Tirzitis, Gunars / Tirzite, Dace / Cipak, Ana / Khoschsorur, Gholam A / Waeg, Georg / Tatzber, Franz / Scukanec-Spoljar, Mira / Zarkovic, Neven

    European journal of pharmacology

    2006  Volume 537, Issue 1-3, Page(s) 12–19

    Abstract: 1,4-Dihydroisonicotinic acid derivatives (1,4-DHINA) are compounds closely related to derivatives of 1,4-dihydropyridine, a well-known calcium channel antagonists. 1,4-DHINA we used were derived from a well-known antioxidant Diludin. Although some ... ...

    Abstract 1,4-Dihydroisonicotinic acid derivatives (1,4-DHINA) are compounds closely related to derivatives of 1,4-dihydropyridine, a well-known calcium channel antagonists. 1,4-DHINA we used were derived from a well-known antioxidant Diludin. Although some compounds have neuromodulatory or antimutagenic properties, their activity mechanisms are not well known. This study was performed to obtain data on antioxidant and bioprotective activities of: 2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydroisonicotinic acid (Ia); sodium 2-(2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridine-4-carboxamido)glutamate (Ib) and sodium 2-(2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridine-4-carboxamido)ethane-sulphate (Ic). 1,4-DHINA's activities were studied in comparison to Trolox by: N,N-Diphenyl-N'-picrylhydrazyl (DPPH*), deoxyribose degradation, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radical scavenging and antioxidative capacity assays; copper-induced lipid peroxidation of cultured rat liver cells (malondialdehyde determination by high performance liquid chromatography and 4-hydroxynonenal-protein conjugates by dot-blot); (3)H-thymidine incorporation and trypan blue assay for liver cells growth and viability. In all assays used Ia was the most potent antioxidant. Ia was also a potent antioxidant at non-toxic concentrations for liver cell cultures. It completely abolished, while Ic only slightly decreased copper-induced lipid peroxidation of liver cells. Thus, antioxidant capacities are important activity principle of Ia, which was even superior to Trolox in the cell cultures used, while activity principles of Ic and Ib remain yet to be determined.
    MeSH term(s) Animals ; Antioxidants/pharmacology ; Cell Survival/drug effects ; Cells, Cultured ; Copper/pharmacology ; Female ; Isonicotinic Acids/pharmacology ; Lipid Peroxidation/drug effects ; Liver/drug effects ; Liver/metabolism ; Malondialdehyde/metabolism ; Oxidative Stress/drug effects ; Rats ; Rats, Wistar
    Chemical Substances Antioxidants ; Isonicotinic Acids ; Malondialdehyde (4Y8F71G49Q) ; Copper (789U1901C5)
    Language English
    Publishing date 2006-05-10
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 80121-5
    ISSN 1879-0712 ; 0014-2999
    ISSN (online) 1879-0712
    ISSN 0014-2999
    DOI 10.1016/j.ejphar.2006.03.004
    Database MEDical Literature Analysis and Retrieval System OnLINE

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