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    Free Radicals and AntioxidantsNOW IN
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    Isolation, identification and radical scavenging activity of phlorotannin derivatives from brown algae, Ecklonia maxima: An experimental and theoretical study

    Henry M. Mwangi1, Jan Van Der Westhuizen2, Jeanine Marnewick3, Wilfred T. Mabusela1,4★, Mwadham M. Kabanda5, Eno E. Ebenso5★ Corresponding author

    1. 1Department of Chemistry, University of the Western Cape, Bellville 7535, South Africa.
    2. 2Department of Chemistry, University of Free State, Bloemfontein 9301, South Africa.
    3. 3Antioxidant and Oxidative Stress Unit, Cape Peninsula University, Bellville 7535, South Africa.
    4. 4South African Herbal Science and Medicine Institute, University of the Western Cape, Bellville 7535, South Africa.
    5. 5Department of Chemistry, North-West University (Mafikeng Campus), Mmabatho 2735, South Africa.

    CORRESPONDENCE

    Wilfred T. Mabusela

    Department of Chemistry, University of the Western Cape, Bellville 7535, South Africa.

    wmabusela@uwc.ac.za

    Received: 17-06-2013; Revised: 23-10-2013; Accepted: 11-12-2013.

    Volume 3, Issue 2S · pp. s1–s10 · PUBLISHED · DOI: 10.1016/j.fra.2013.10.006

    View on Free Rad. Antiox. original site ↗

    ABSTRACT

    Aim & background: Phlorotannins are a family of polyphloroglucinols with numerous biological activities including anticancer, antimalarial and antioxidant. They are highly sought for utilization in food ingredients, animal feeds, fertilizers and medicines. This work reports the isolation, from brown algae, of four phlorotannin derivatives namely phloroglucinol (1), eckol (2), 7-phloroeckol (3) and 2-phloroeckol (4). Their radical scavenging activity was assayed to elucidate their capacity to scavenge free radical species. Their structural and electronic features were then compared across structures to provide an explanation for the differences in their radical scavenging properties. Moreover, the two main radical scavenging mechanisms, namely hydrogen atom transfer (HAT) and electron transfer (ET), were checked to determine the preferred mode of radical scavenging. Methods:Polyphenols were determined spectrophotometrically according to the FolineCiocalteu colorimetric methods and the antioxidant assays were determined by means of ORAC assay and the Trolox equivalent antioxidant capacity (TEAC) assay. Theoretical studies were performed by means of the Density Functional Theory (DFT) method. Results:Theoretical predictions indicate that the radical scavenging activities follow the order 1 < 2 < 4 < 3. Theoretical study also indicates that ET mechanism could be more significant than HAT mechanism because of the high BDE values. Conclusion: Overall, the results suggest that the position of substitution of phloroglucinol unit on eckol (2) plays a significant role in determining the radical scavenging ability of the resulting eckol derivatives.

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      Mwangi, H. M., Westhuizen, J. V. D., Marnewick, J., Mabusela, W. T., Kabanda, M. M., & Ebenso, E. E. (). Isolation, identification and radical scavenging activity of phlorotannin derivatives from brown algae, Ecklonia maxima: An experimental and theoretical study. Free Radicals and Antioxidants, 3(2S), s1–s10. https://doi.org/10.1016/j.fra.2013.10.006