Characterization of ulvan extracts to assess the effect of different steps in the extraction procedure

• Published in: Carbohydrate polymers 2012-04, Vol.88 (2), p.537-546
• Main Authors: Costa, Carina, Alves, Anabela, Pinto, Paula R., Sousa, Rui A., Borges da Silva, Eduardo A., Reis, Rui L., Rodrigues, Alírio E.
• Format: Article
• Language: English
• Subjects: Algae; Applied sciences; Biological and medical sciences; Carbohydrates; Chemical constitution; chemical structure; Chlorophycota; Exact sciences and technology; Extraction; Fundamental and applied biological sciences. Psychology; Glucose; glucuronic acid; Green algae; molecular weight; Natural polymers; Physicochemistry of polymers; Plant physiology and development; Polysaccharide characterization; Polysaccharides; proteins; Purification; Rhamnose; Starch and polysaccharides; Ulva lactuca; Ulvan; Xylose
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2011.12.041

► A sulfated polysaccharide, ulvan, was extracted from green algae and purified. ► The composition were assessed by multiple and complementary methodologies. ► Acid methanolysis was improved to obtain the maximum yield on released monosaccharides. ► Ulvan is highly sulfated and composed by rhamnose, xylose, glucuronic and iduronic acids. ► The polysaccharide is not affected by the different steps in the extraction procedure. An effective application development of the polysaccharide ulvan requires a comprehensive knowledge about the influence of the extraction process on composition of the extracts and in ulvan itself. In this context, the two main objectives of the present work are (1) the establishment of an efficient extraction process for ulvan and (2) development of an accurate characterization methodology to evaluate the extract composition and ulvan content. Three ulvan-rich extracts obtained by different schemes of extraction were studied. The methodology for the analysis was improved and a detailed analysis of extracted ulvan was provided. The polysaccharide is rich in ulvanobiuronic acid 3-sulfate type A [→4)-β-d-GlcAp-(1→4)-α-l-Rhap 3S-(1→], with minor amounts of ulvanobiuronic acid 3-sulfate type B [→4)-α-l-IdoAp-(1→4)-α-l-Rhap 3S-(1→]. The extract with the higher degree of purification is a high molecular weight polysaccharide (790kDa) composed of rhamnose (22.4%), glucuronic acid (22.5%), xylose (3.7%), iduronic acid (3.1%) and glucose (1.0%). It is highly sulfated (32.2%) and contains 1.3% of proteins and 10.3% of inorganic material. Applying simple extraction scheme it was possible to obtain an extract from green algae with high content of ulvan without affecting the overall chemical structure of the polysaccharide.