Structural characterization and immunostimulating activity of a levan-type fructan from Curcuma kwangsiensis

Abstract A fructan designated as CKNP with apparent molecular weight of 5.3 kD was isolated from the hot water extract of Curcuma kwangsiensis through a combination of ion-exchange chromatography on DEAE 650 M and gel filtration on Superdex G-200. CKNP was characterized by chemical derivatization as well as HPLC, GC, and GC–MS technologies. Structural studies revealed that CKNP is composed predominately of fructose (96.8%) and a small amount of glucose (3.2%) with a degree of polymerization (DP) of 30–31. It was deduced to be a levan-type fructan containing a backbone composed of (2 → 6)-linked β - d -Fru f residues and single β - d -Fru f residues as side chains branched at the O -1 position along the backbone. Preliminary in vitro bioactive tests on RAW 264.7 murine macrophage cells revealed that the levan-type fructan from C. kwangsiensis shows significant immunostimulating activity based on its ability to stimulate macrophage proliferation and enhance phagocytosis.