Characterization of Red Seaweed Extracts Treated by Water, Acid and Alkaline Solutions

Abstract

Abstract Seaweed contained health functional polysaccharides and polyphenols. Five extracts were prepared from red seaweed Melanothamnus somalensis; two of these were aqueous at 20°C (F1) and 70°C (F2), followed by acid (F3), alkali (F4) and acid-washed (F5) treatments. Molecular characteristics of extracts were measured by high-performance liquid chromatography and Fourier transform infrared (FTIR) analyses. Health functionality was determined by sulfate and polyphenol contents, and thermal characteristics were determined by modulated differential scanning calorimetry. Extract F3 contained the highest levels of sulfate followed by F2, F1, F4 and F5, respectively. Similarly, F3 contained the highest polyphenol followed by F4, F2, F1 and F5, respectively. Molecular weight distribution of F1 showed wider distribution of sizes (MW: 1.0 × 103 – 3.0 × 107), and F5 showed a sharp peak (MW: 3.1 × 103); whereas F2, F3 and F4 indicated bimodal distribution. FTIR indicated that all fractions contained agar except F5 and sulfate ester group was attached to carbon 6 of the saccharide.