Determination and Comparison of Chemical Composition and Antioxidant Capacity of Fucoidan Extracted from Three Species of Seaweed
Due to the high percentage of people suffering in a sub-healthy state in the world, bioactive compounds extracted from natural products have been largely developed into healthy products and released in the market, especially for seaweed products. Fucoidan extracted from brown seaweed is a sulphate polysaccharide with a variety of bioactivities including antioxidant, anticancer, antibacterial and anticoagulant activities. Undaria pinnatifida as a type of brown seaweed has been accidentally introduced into New Zealand, and this type of seaweed can be another source of fucoidan to potentially develop novel nutraceutical products based on its bioactive constituents. Therefore, the main aim of this study was to focus on the fucoidan extracted from New Zealand sporophyll Undaria pinnatifida, and to determine and compare its chemical composition and biological activities with other commercial fucoidan samples of different origin and species. Seven samples were involved in this study and listed in the following table. The fucoidan extract applied in AUT for S-7 was that seaweed Undaria pinnatifida first was treated with hot water at 70 degree as the conventional hot water extraction method, then the fucoidan precipitate was obtained by the presence of ethanol. Number Sample Name Sample Description Species Vendor 1 S-1 Fucoidan (>98%), ShanDong Laminaria japonica SHANGDONGJIEJING GROUP, ShanDong, China 2 S-2 Fucoidan (>98%), ShanDong Ascophyllum nodosum var mackayi SHANGDONGJIEJING GROUP, ShanDong, China 3 S-3 Fucoidan (>98%), ShanDong Undaria pinnatifida SHANGDONGJIEJING GROUP, ShanDong, China 4 S-4 Fucoidan Dietary Supplement (70%), New Zealand Sporophyll, Undaria pinnatifida New Zealand 5 S-5 Seaweed Powder, New Zealand Undaria pinnatifida KDI INGREDIENTS - Nutraceutical Design, New Zealand 6 S-6 Fucoidan (95%), Beijing Undaria pinnatifida AlgaNovo International Co.,Ltd, Beijing, China 7 S-7 Sporophyll Fucoidan Sporophyll, Undaria pinnatifida Extracted from AUT Analytical Chemistry Research Laboratory
From the analysis results of chemical composition (including monosaccharide analysis, total sugar, protein contents, sulphate contents and contents of metal elements), the monosaccharide composition from the structure of all fucoidan samples include mannose, ribose, galactose, glucose, glucuronic acid, arabinose, xylose and fucose, with the exception of fucoidan sample S-5. In addition, the contents of galactose and fucose in all fucoidan samples are higher as compared to other monosaccharide contents. The fucose content from the fucoidan sample S-7 was 44.6 %, and its percentage content was the highest value in all the monosaccharide contents. Results of the total sugar analysis indicated that there were no significant differences between the total sugar content in the fucoidan samples of different seaweed origin and species. Furthermore, due to lower purity of fucoidan in S-4 and S-5, the content of total sugar was significantly lower than other fucoidan samples. Regarding the analysis result of protein content, there was also no significant and statistical difference amongst the majority of commercial fucoidan samples, aside from fucoidan sample S-7 which contains the highest protein percentage (approximately 4.0%). For the analysis result of sulphate, fucoidan sample S-7 contains the highest percentage of sulphate contents (32.0 %) as compared to the other fucoidan commercial products. Collectively, the aforementioned results may indicate that the three factors which relate to differences between the composition of fucoidan include the extraction method, the seaweed species and its origin. According to the metal analysis results, higher amounts of K, Ca, Mg, Zn and Fe were found in all fucoidan samples. Toxic metal element content, including Pb, As, Hg, Cd and Cr, of fucoidan sample S-7 was significantly and statistically lower than the other fucoidan samples. This suggested that the fucoidan sample S-7 is safer than the other samples, while also implying that sporophyll Undaria pinnatifida can be less toxic than other sources of fucoidan. Such data could be used as a reference for fucoidan nutraceutical product formulation design to match safety guidelines. Pertaining to antioxidant activity, all fucoidan samples generated antioxidant effects in the dose-dependent manner for both the DPPH and the hydroxyl radical scavenging assays. Notably, because fucoidan sample S-7 had the highest sulphate content, it also generated the highest antioxidant effects in comparison to all other fucoidan samples. This was especially true in the treatment concentration range of 0 to 62.5 µg/mL, where the antioxidant effect significantly increased in the DPPH assay, suggesting that this concentration range is the most effective at producing antioxidant effects from S-7. Additionally, as compared to the antioxidant effect between the DPPH results (primary antioxidant activity) and the hydroxyl radical results (secondary antioxidant activity), all fucoidan samples generated higher secondary antioxidant activity, indicating that these samples were better secondary (or preventive) antioxidants which provide a proton, scavenge reactive oxygen, and decompose hydroxyl radicals. In conclusion, unique environmental conditions made the fucoidan sample extracted by New Zealand sporophyll Undaria pinnatidifa different in its chemical composition, with higher antioxidant activity and less presence of toxic metal elements. Therefore, the sporophyll Undaria pinnatifida from New Zealand is presented as the better source to develop fucoidan-based nutraceutical products.