Sulphated polysaccharide extracted from the Mediterranean edible seaweed Caulerpa racemosa: structural, rheological and biological features

Abstract

This study was intended to estimate the proximate nutritional composition of the green seaweed C. racemosa and to operate microwave processing (180–220 °C, 3 min) for the extraction of sulphated polysaccharides. Polymer fractions boasting the highest yields were selected to evaluate their structural and rheological features. Cell viability of the polysaccharide (200 °C) was examined on NCTC clone 929 mouse fibroblasts (0.25–1.0 mg/mL) and further on RAW264.7 murine macrophages (62.5–500 μg/mL). Its anti-inflammatory effect was evaluated in vitro by monitoring the levels of nitric oxide (NO). The highest polymer yield (32.3 %) was found for samples treated at (200 °C, 32.3 %), followed by (180 °C, 17 %). Structural analysis demonstrated that these biopolymers are structurally like those reported for sulphated polyssacharides derived from other green seaweeds, with molecular weights between 149 kDa and 37.6 kDa. The highest TPC (93 mg GAE/g) and antioxidant capacity were obtained at 220 °C. The greatest sulphate (338.3 mg K₂SO₄/g extract) and protein (26.5 mg BSA/g extract) rates were found at 180 °C. All polymer doses examined were non-toxic to NCTC clone 929 murine fibroblasts or RAW 264.7 cells. NO inhibition (%) revealed that the biopolymer had a substantial in-vitro anti-inflammatory impact with an IC₅₀ of (200 μg/mL).