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A comparative assessment of the activity and structure of phlorotannins from the brown seaweed Carpophyllum flexuosum

Zhang, Rui, Yuen, Alexander K.L., Magnusson, Marie, Wright, Jeffrey T., de Nys, Rocky, Masters, Anthony F., Maschmeyer, Thomas
Algal research 2018 v.29 pp. 130-141
2,2-diphenyl-1-picrylhydrazyl, Carpophyllum flexuosum, Ecklonia radiata, antioxidant activity, antioxidants, ascorbic acid, cell structures, chemical species, high performance liquid chromatography, macroalgae, mass spectrometry, microwave treatment, nuclear magnetic resonance spectroscopy, scanning electron microscopy
The extraction and antioxidant activity of phlorotannins from the brown seaweeds Carpophyllum flexuosum, Carpophyllum plumosum and Ecklonia radiata was investigated to identify an optimised extraction process for novel anti-oxidant extracts. Subsequently, the composition of the most active phlorotannin extracts was determined. Microwave assisted extraction (MAE) using water was the most efficient extraction process with shorter processing times and a higher purity product than obtained with any of the other methods tested. MAE resulted in the fast, effective decomposition of the cellular structure, as identified through scanning electron microscopy (SEM), and this related directly to the efficiency of extraction. Phlorotannins extracted from C. flexuosum by MAE had the strongest antioxidant activity (62.1mggallicacidequivalents(GAE)/g dw of seaweed) and more than 5.5-fold greater 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability than ascorbic acid after 7-day incubation periods at 30°C and at 60°C. Six major chemical species of phlorotannin, belonging to the fuhalol group, were identified within the MAE extract using NMR and HPLC-MS. The results confirm phlorotannins from C. flexuosum to be promising natural, bio-derived and bio-compatible antioxidants, while identifying the most effective method to extract the constituents and retain antioxidant activity.