Chemical structure and biological activity of the (1 → 3)-linked ß-D-glucan isolated from marine diatom Conticribra weissflogii.

Several polysaccharides are considered to be "biological response modifiers" (BRM) - these refer to biomolecules that augment immune responses and can be derived from a variety of sources. Microalgae produce a diverse range of polysaccharides and could be an excellent source of BRM. Here, we describe the chemical structure and biological activity of water-soluble polysaccharide isolated from the marine diatom Conticribra weissflogii. Using chemical and NMR spectroscopic methods, the polysaccharide was identified as a (1 â†’ 3)-linked ß-D-glucan with a low proportion of C-6 substitution by single ß-glucose units. The biological activity of this low molecular weight ß-glucan (11.7 kDa) was investigated with respect to glioblastoma cell lines (U87 MG and U251) and macrophages (RAW 264.7). We observed that this ß-D-glucan did not exhibit cytotoxic activity against glioblastoma cells, but did enhance the phagocytic activity of macrophages, suggesting that it possesses immunomodulatory properties.

Structural features of polysaccharides from edible jambo (Syzygium jambos) fruits and antitumor activity of extracted pectins.

Jambo is a tropical fruit cultivated in Southeast Asia and tropical regions of America and Africa. After extraction, its polysaccharides were structurally characterized. Water soluble polysaccharides (WSP) were composed of GalA:Ara:Gal:Glc:Rha in 51:22:16:5:6 molar ratio, indicating the presence of pectic polysaccharides. Methylation analysis and NMR spectroscopy indicated the presence of homogalacturonan (HG), type II arabinogalactan and type I rhamnogalacturonan (RG-I). The HG/RG-I ratio was 88%, indicating greater amounts of smooth than hairy pectic regions. Hemicellulosic polysaccharides were extracted from the residue and fractionated by freeze-thaw procedure in two fractions (ASP-S and ASP-I). ASP-S was composed of Glc:Gal:Xyl:Ara:Man:Fuc:UA in a 45:16:20:3:8:5:2 molar ratio. Methylation analysis and 13C NMR spectroscopy indicated xyloglucan, xylan and mannan. Their relative proportion estimated on sugar linkage was 89%, 6% and 3%, respectively. ASP-I was composed mainly of xylose (99.5%) and its 13C NMR indicated a linear (1 → 4)-ß-D-xylan. The biological activity of WSP was tested in Ehrlich tumor-bearing mice. After 21 days of oral treatment, the doses of 150 and 250 mg/kg WSP reduced expressively the tumor growth, similarly to the positive control methotrexate, and improved the body weight of tumor-bearing mice. Further studies are necessary to investigate the mechanisms of the WSP antitumor effect.

Arabinogalactan from edible jambo fruit induces different responses on cytokine secretion by THP-1 macrophages in the absence and presence of proinflammatory stimulus.

Syzygium jambos is an Indo-Malaian found in many tropical countries and it is mainly composed of carbohydrates. Fraction PF-WSP and SF-WSP were obtained by aqueous extraction followed by Fehling's treatment. Monosaccharide analysis showed that fraction PF-WSP has a high content of uronic acids (90%) and fraction SF-WSP presented mainly galactose (39.1%) and arabinose (34.2%), as neutral sugars and 9% of galacturonic acid. The presence of type II arabinogalactan in SF-WSP was evidenced by methylation analysis and 13C/1H HSQC NMR experiments. Immunomodulating properties of SF-WSP was investigated. It decreases THP-1 macrophage viability at the highest concentration tested (200µg/mL). We then tested non-cytotoxic concentrations of SF-WSP on THP-1 cytokine production in the presence and absence of LPS. The results showed that SF-WSP increased TNF-α, IL-1ß and IL-10 secretion in a concentration-dependent manner as well as attenuated the inflammatory response induced by LPS at the highest concentration (100µg/mL). These results contribute to elucidate the effects of fruit pectic polysaccharides on immune cells.