Abstract:Gracilaria lemaneiformis is an important source of agar, but its non-agar part is often ignored. A non-agar polysaccharide fraction was isolated from Gracilaria lemaneiformis, and its primary structure and in vitro biological activity were preliminarily explored. The non-agar polysaccharide fraction was isolated through the conventional process and was named GCP. The results of pre-column derivatization and high performance liquid chromatography (HPLC) suggested that GCP was composed of galactose. Periodate oxidation and Smith degradation showed that the monosaccharide group was linked by 1→3 and 1→4 glycosidic bonds. I2-KI test and a Congo red test showed that GCP had a large number of branches and long side chains, and the spatial configuration was a single helix or a coil in its free form. A main component, GCP-2 with a molecular weight of 1.05 × 104 U, was obtained after further purification using DEAE Sepharose Fast Flow (DEAE FF) column chromatography. Splenocyte damage and splenocyte proliferation assays were used to analyze the cell immunomodulatory activities of GCP and GCP-2. GCP showed a slightly higher activity than GCP-2 in the test concentration range. The highest splenocyte proliferation rate and the greatest protection rate for damaged splenocytes by GCP were 7.45% and 51.50%, respectively. This study shows that non-agar polysaccharides have good cellular immunomodulatory activity and a strong cell protective effect. In addition, they could be used as raw materials for production of new drugs and health products.
