Influence of the uronic acid composition on the gastroprotective activity of alginates from three different genus of Tunisian brown algae

- Sodium alginates were extracted and purified from three Mediterranean brown algae.
- Physico-chemical characterization and uronic acid composition of the extracted polysaccharides were performed.
- The influence of the M/G ratio of alginates on their anti-ulcerogenic effects was investigated.

Alginates from three genus of Tunisian brown algae were isolated and characterized by size exclusion chromatography and Solid-state NMR spectroscopy. Alginate from Padina pavonica (APP) had the highest molecular weight (Mw) with 147,000 g/mol while it was 85,000 g/mol for alginate from Cystoseira compressa (ACC) and 58,000 g/mol for alginate from Dictyopteris membranaceae (ADM). The mannuronate (M) to guluronate (G) ratios were estimated from spectral deconvolution of the 13C CP/MAS spectra and the results has shown that all the extracts are mannuronic acid-rich alginates with M/G ratio increased in the order ADM - ACC - APP. An interesting gastroprotective effect was observed for the extracts; ADM and ACC exhibited the highest inhibition of gastric lesions, at 50 mg/kg, with 83.41% and 75.39% respectively. Otherwise, it has been shown that the gastroprotective effect of alginates depends mainly on their uronic acid composition.