Extracted and depolymerized alginates from brown algae Sargassum vulgare of Lebanese origin: chemical, rheological, and antioxidant properties

Abstract

International audiencePurified sodium alginate (PS alginate) was isolated from the brown seaweed Sargassum vulgare collected from the Lebanese Mediterranean coast and then depolymerized into homopolymeric polyguluronate (PolyG) and polymannuronate (PolyM) blocks by controlled acid hydrolysis. These fractions of PS alginate issued from S. vulgare were characterized in terms of composition and structure by SEC, elemental analysis, FTIR and 1H and 13C NMR spectroscopy. An alginate with a low content of protein (\textless0.62 %) and a molecular weight of 110 200 g mol-1 was identified as sole polysaccharide. Depolymerized PS alginate fractions, PolyG (32.6 %) and PolyM (22.3 %), were found to have close molecular weights, of 7500 and 6900 g mol-1, respectively. From NMR analysis, values of F G, F M, M/G ratio, F GG, F MM, and F GM (or F MG) blocks were determined and compared with those of alginates from S. vulgare of Brazilian origin and other Sargassum species. Our PS alginate appeared different from the Brazilian S. vulgare alginate, with a lower M/G ratio (0.785 instead of 1.27), a predominance of the G blocks (F G and F GG \textgreater 0.5) instead of the M blocks, and it showed more similarity to the composition of some alginates extracted from other species of Sargassum. High G or M contents (≥80 %) were measured from PolyG and PolyM blocks, respectively. The viscosity of the PS alginate and its fractions PolyG and PolyM was determined. PS alginate from S. vulgare of Lebanese origin showed a Newtonian flow behavior for concentration lower than 0.5 % in 0.1 M NaCl solution, while a shear-thinning pseudoplastic behavior is observed for concentration range between 0.75 and 10 %. Also, storage (G′) and loss (G″) moduli were studied for two concentrations of PS alginate solutions (5 and 10 %). Antioxidant properties of the non-depolymerized and depolymerized alginates were evaluated by determining the scavenging ability of the stable radical DPPH (2,2-diphenyl-1 picrylhydrazyl). Clearly, the results demonstrated differences in radical scavenging efficacy between PolyG and PolyM fractions. The higher hydroxyl radical scavenging activity was observed for the PolyG fractions (~92 % at 2 mg mL-1) and this activity was comparable with those of standard antioxidants. These PolyG fractions could be valuable in foods or pharmaceutical products as alternatives to synthetic antioxidant

Functional bioreactor characterization to assess potentials of nanocomposites based on different alginate types and silver nanoparticles for use as cartilage tissue implants

“…Alginate is a natural polysaccharide that easily forms biocompatible and hydrophilic hydrogels with high sorption capacity. However, alginate as a natural product derived from brown seaweed differs in composition, molecular weight and physical properties depending on the algae species and age, the harvesting season, and ecological system (geographical origin) . More homogeneous alginate composition is obtained by biosynthesis using two genera of bacteria ( Pseudomonas and Azotobacter ), but still some variations and different material properties could appear .…”

“…However, alginate as a natural product derived from brown seaweed differs in composition, molecular weight and physical properties depending on the algae species and age, the harvesting season, and ecological system (geographical origin). [17][18][19] More homogeneous alginate composition is obtained by biosynthesis using two genera of bacteria (Pseudomonas and Azotobacter), but still some variations and different material properties could appear. 20,21 In specific, the content and arrangement of guluronic (G) and mannuronic (M) acid residues influence Na-alginate solution viscosity as well as mechanical and swelling properties of resulting Ca-alginate hydrogels so that alginates with higher G contents generally yield stronger hydrogels.…”

Therapeutic compression materials and wound dressings for chronic venous insufficiency: A comprehensive review

“…Alginate is a natural anionic polysaccharide heteropolymers (Figure ) (Bruchet & Melman, ; Sun & Tan, ) that can be extracted from brown algae—a nontoxic, biodegradable, and highly biocompatible material (Sari‐Chmayssem et al, ). Brown algae is widely applied in drug delivery and tissue regeneration because of its unique gel‐formation property.…”

Kesan Kaedah Pemendakan Berbeza terhadap Ciri Fizikokimia dan Aktiviti Antioksidan Alginat daripada Sargassum sp.

“…dalam kajian ini ataupun alginat komersial mempunyai kelakuan kelikatan pseudoplastik (McHugh 1987) iaitu kelakuan penipisan ricih. Sari-Chmayssem et al (2015) telah melaporkan bahawa larutan alginat mempunyai kelakuan penipisan ricih dan kajian mereka telah membuktikan kelikatan larutan alginat menurun dengan peningkatan kadar ricih.…”