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

Authors

  • Henry M. Mwangi Department of Chemistry, University of the Western Cape, Bellville 7535, South Africa
  • Jan Van Der Westhuizen Department of Chemistry, University of Free State, Bloemfontein 9301, South Africa
  • Jeanine Marnewick Antioxidant and Oxidative Stress Unit, Cape Peninsula University, Bellville 7535, South Africa
  • Wilfred T. Mabusela [a] Department of Chemistry, University of the Western Cape, Bellville 7535, South Africa. [d] South African Herbal Science and Medicine Institute, University of the Western Cape, Bellville 7535, South Africa.
  • Mwadham M. Kabanda Department of Chemistry, North-West University (Mafikeng Campus), Mmabatho 2735, South Africa
  • Eno E. Ebenso Department of Chemistry, North-West University (Mafikeng Campus), Mmabatho 2735, South Africa

Keywords:

Brown algae , Ecklonia maxima , Phlorotannins , Radical scavenging activity , Hydrogen atom transfer mechanism

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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Total phenolic contents (in mg GAE/g) of some extracts and yields of compounds isolated from ethanolic fraction of Ecklonia maxima.

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Published

2013-10-15

How to Cite

Henry M. Mwangi, Jan Van Der Westhuizen, Jeanine Marnewick, Wilfred T. Mabusela, Mwadham M. Kabanda, & Eno E. Ebenso. (2013). Isolation, identification and radical scavenging activity of phlorotannin derivatives from brown algae, Ecklonia maxima: An experimental and theoretical study. Free Radicals and Antioxidants, 3(2 (Suppl), S1-S10. Retrieved from https://antiox.org/index.php/fra/article/view/150