The Content, Antioxidant Activity, and Structural Characteristics of Sodium Alginate Extracting from Sargassum polycystum Grew in Vietnam: Effect of Various Extraction Conditions
Nguyen Dinh Thuat
Nha Trang Institute of Technology Application and Research, VAST, 650000 Khanh Hoa, Vietnam and Graduate University of Science and Technology, VAST, 100000 Ha Noi, Vietnam.
Vu Ngoc Boi
Faculty of Food Science, Nha Trang University, 650000 Khanh Hoa, Vietnam.
Nguyen Xuan Hoan
Ho Chi Minh City University of Food Industry, 700000 Ho Chi Minh, Vietnam.
Dang Thi Thanh Tuyen
Faculty of Food Science, Nha Trang University, 650000 Khanh Hoa, Vietnam.
Do Thuy Kieu
Faculty of Food Science, Nha Trang University, 650000 Khanh Hoa, Vietnam.
Nguyen Kim Nguyen
Faculty of Food Science, Nha Trang University, 650000 Khanh Hoa, Vietnam and Tuy Hoa city medical center, 56100 Tuy Hoa, Vietnam.
Nguyen Ngoc Bao Huy
Nha Trang Institute of Technology Application and Research, VAST, 650000 Khanh Hoa, Vietnam and Graduate University of Science and Technology, VAST, 100000 Ha Noi, Vietnam.
Pham the Trinh
Department of Science and Technology, 63000 Dak Lak, Dak Lak, Vietnam.
Pham Thanh Thuan
General Surgery Department, Ninh Thuan Provincial General Hospital, 59000 Ninh Thuan, Vietnam.
Dang Xuan Cuong *
Nha Trang Institute of Technology Application and Research, VAST, 650000 Khanh Hoa, Vietnam and Graduate University of Science and Technology, VAST, 100000 Ha Noi, Vietnam and Ho Chi Minh City University of Food Industry, 700000 Ho Chi Minh, Vietnam.
*Author to whom correspondence should be addressed.
Abstract
Introduction: Alginate is a biopolymer commonly in brown algae, high content, diversity in structure and bioactivity. They are applied to other fields such as food, functional food, pharmaceuticals, and heavy industry and extracted from Sargassum, Laminarin, Tubinaria and Sargassum polycystum species commonly grow in the world than another genus. The content, the antioxidant activity, and the physical chemistry properties of alginate extracting from the species did not exhibit in the previous studies.
Methods: The study focused on the impact of various extraction conditions (temperature (40 to 90,oC), time (01 to 06, hours), the solvent-to-material ratio (10/1 to 40/1, v/w), solvent pH (8, 9, 10), and numbers of extraction (1, 2, and 3 times) on alginate content and its antioxidant activity, also evaluated sugar compositions, average molecular, viscosity, and 13C-NMR spectrum characteristics of alginate.
Results: The results showed that the suitable condition for the extraction of alginate was for 4 hours at 60oC with the ratio of Na2CO3 (pH 9)-to-material (40/1, v/w) and one number of extraction. The highest alginate content was 176.22 mg uronic acid equivalent/g DW, corresponding to antioxidant activity (188.54 mg ascorbic acid equivalent/g DW). Alginate possessed the intrinsic viscosity (271.86, ƞ) and the average molecular weight (78.6, kD). Different sugar compositions of antioxidant alginate were fructose, fucose, mannose, galactose, rhamnose, mannose, and glucose. The 13C-NMR spectrum of antioxidant alginate exhibited chemical shifts of C sites of D-mannuronic (M) and L-guluronic (G), corresponded to C1, C2, C6, and C2, C3, C4, C5, C6, respectively.
Conclusion: Alginate is non-toxic, therefore, antioxidant alginate extracting from brown algae Sargassum polycystum grown in Vietnam is a potential in functional food and pharmaceuticals.
Keywords: Alginate, antioxidant, extraction, Sargassum polycystum, structure