Sulfated Polysaccharide Extracted from the Green Algae Codium bernabei: Physicochemical Characterization and Antioxidant, Anticoagulant and Antitumor Activity

Abstract

Codium bernabei is a green alga that grows on Chilean coasts. The composition of its structural polysaccharides is still unknown. Hence, the aim of this work is to isolate and characterize the hot water extracted polysaccharide fractions. For this purpose, the water extracts were further precipitated in alcohol (TPs) and acid media (APs), respectively. Both fractions were characterized using different physicochemical techniques such as GC-MS, GPC, FTIR, TGA, and SEM. It is confirmed that the extracted fractions are mainly made of sulfated galactan unit, with a degree of sulfation of 19.3% (TPs) and 17.4% (ATs) and a protein content of 3.5% in APs and 15.6% in TPs. Other neutral sugars such as xylose, glucose, galactose, fucose, mannose, and arabinose were found in a molar ratio (0.05:0.6:1.0:0.02:0.14:0.11) for TPs and (0.05:0.31:1.0:0.03:0.1:0.13) for ATs. The molecular weight of the polysaccharide samples was lower than 20 kDa. Both polysaccharides were thermally stable (Tonset > 190 °C) and showed antioxidant activity according to the ABTS•+ and DPPH tests, where TPs fractions had higher scavenging activity (35%) compared to the APs fractions. The PT and APTTS assays were used to measure the anticoagulant activity of the polysaccharide fractions. In general, the PT activity of the TPs and APs was not different from normal plasma values. The exception was the TPs treatment at 1000 µg mL−1 concentration. The APTTS test revealed that clotting time for both polysaccharides was prolonged regarding normal values at 1000 µg mL−1. Finally, the antitumor test in colorectal carcinoma (HTC-116) cell line, breast cancer (MCF-7) and human leukemia (HL-60) cell lines showed the cytotoxic effect of TPs and APs. Those results suggest the potential biotechnological application of sulfate galactan polysaccharides isolated from a Chilean marine resource.

Keywords: Codium bernabei; anticoagulant activity; antioxidant capacity; cytotoxic effect; polysaccharides; sulfated galactans.

Figure 1

GC-MS chromatograms of the TPs (A) and APs (B) polysaccharides fractions isolated from C. bernabei. Monosaccharide identified are as follows: 1 Arabinose; 2 Fucose; 3 Xylose; 4 Mannose; 5 Galactose; 6 Glcucose.

Figure 2

FTIR spectra of the polysaccharide fractions isolated from C. bernabei macroalgae.

Figure 3

TGA (A) and DTG (B) curves of the polysaccharide fractions isolated from C. bernabei macroalgae.

Figure 4

Scanning electron microscopy (SEM) images of TPs (A,B) and APs (C,D) polysaccharide fractions isolated from Codium bernabei.

Figure 5

Antioxidant activity of polysaccharides extracted from C. bernabei. (A) DPPH radical scavenging (%) activity; (B) ABTS^•+ radical scavenging activity (%). Ascorbic acid was used as Control. Values are presented as mean ± SD (n = 4). The different letters above the bars of each parameter are significantly different at p < 0.05 (Tukey’s test).

Figure 6

Cell viability (% survival) exposed to different concentrations of polysaccharide fractions from Codium bernabei. (A) Human colon cancer cell line (HTC-116), (B) Breast cancer cell line (MCF-7), (C) Human leukaemia cells (HL-60). The same letter indicate no significant difference at p < 0.05 (Tukey’s test).