Screening South Australian Native seaweeds for antioxidant activities

Author: Navjot Kaur .

., Navjot Kaur, 2016 Screening South Australian Native seaweeds for antioxidant activities, Flinders University, School of Health Sciences

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Sea weeds provide an attractive opportunity as a utilization resource due to their fast growth rates comparatively terrestrial plants and wider applications in natural health and cosmeceuticals. South Australia is one of the richest region in marine macroalgal diversity throughout the world which contain approximately 123 species of chlorophyta (green algae), 203 species of Phaeophyta (brown algae) and about 800 species of Rhodophyta (red algae). This study illustrates the information regarding polyphenolic compounds and antioxidant activities of the selected seventeen South Australian native seaweeds. The main aim of the study is to extract polyphenols rich compounds from selected seventeen South Australian native seaweeds to screen antioxidant activities which possess potential applications in health care and cosmeceutical products. The seaweed phlorotannins extracted by 90% ethanol conventional extraction method and yield measured after freeze drying the crude extract at -800C. 0.5g of seventeen selected seaweeds dried biomass used for extraction and according to analysis results of total phenolics content (TPC) antioxidant activities by ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) assay 10g of Ecklonia radiata chose for extraction and analysis at large scale to compare the results with E.radiata (0.5g). Phlorotannin assay used to determine the total phenolics content and results were expressed in phloroglucinol gram equivalents (PGEs) / 100g DSW (dry seaweed weight). Antioxidant activities of selected seventeen seaweeds were obtained by using FRAP and ORAC assay and results are expressed in mmol FeSO4 equivalents (FE) /100g DSW and μmol trolox equivalents (TE) /100g DSW. The phlorotannin assay, FRAP assay and ORAC assay were performed with Mili-Q water and 90% ethanol for comparative results to get the accuracy in result data. On the whole, 90% ethanol tested seaweeds in all chemical assays gave high total phenolics content and antioxidant activities comparatively obtained by Mili-Q water. Five genera of seaweeds gave high phenolics content which ranged from 1.01 to 5.4g PGEs /100g DW of seaweed with mili-Q water and 1.7 to 5.5g PGEs /100g DW of seaweed with 90% ethanol. They were Ecklonia radiata > Ecklonia radiata (10g) > Sargassum sp. > Cystophora monilifera > Cystophora platylobium > Carpoglossum confluens. In terms of FRAP antioxidant activities, [Ecklonia radiata (28.3 mmol FE /100g DSW), Ecklonia radiata (10g) (29.7 mmol FE / 100g DSW) with Mili-Q water] and [E.radiata (57.1 mmol FE/ 100g DSW) and for E.radiata (10g) gave (48.3 mmol FE /100g DSW) with 90% ethanol], [Cystophora monilifera (13.5 mmol FE/ 100g DSW) with MIli-Q water and with 90% ethanol (18.6 mmol FE /100g DSW)] gave high antioxidant activities. On the other hand, Ecklonia radiata, Sargassum sp. and C.monilifera showed high antioxidant activities in ORAC assay with Mili-Q water 623.7 to 794.1 μmol TE/ 100g DSW and with 90% ethanol 80.3 to 820.5 μmol TE /100g DSW. In conclusion, this study successfully identified four South Australian native seaweed species which are best sources of antioxidant activities with the potential of commercial applications of healthcare and cosmeceutical products. Results data indicated that South Australian native seaweeds are potent natural resources in ferric reducing and radical scavenging capacities. These properties are beneficial for the development of nutritional products in pharmaceutical and in cosmeceutical industries.

Keywords: Seaweeds antioxidant activities

Subject: Medical Biotechnology thesis

Thesis type: Masters
Completed: 2016
School: School of Health Sciences
Supervisor: Prof. Wei Zhang