Abstract: The antioxidant activity and cellular immunomodulatory activity of polysaccharide fractions obtained from Lycopi Herba were evaluated in vitro. Two homogenous polysaccharides, designated LHPS1 and LHPS5, were isolated from the crude polysaccharide extract of Lycopi Herba by DEAE-52 and SephadexG-100 column chromatography. The structures and biological activities of LHPS1 and LHPS5 were studied by physicochemical and immunological methods. The results showed that LHPS1 (1.13 × 105 Da) and LHPS5 (7.40 × 104 Da) were acidic polysaccharides, composed of many monosaccharides and galacturonic acid. In terms of total reducing power and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, both polysaccharides had significant antioxidant activity in vitro. Immunoassays indicated that they could activate RAW264.7 cells to produce tumor necrosis factor-α (TNF-α), and promote the proliferation of splenic lymphocytes. Fluorescence immuno-activated transport assay showed that they could regulate immune responses by activating the transcription factor nuclear factor-kappa B (NF-κB) in RAW264.7 cells. In addition, inhibitor neutralization test results showed that the two polysaccharides could activate macrophages by binding to cell surface mannose receptors. Overall, we concluded that LHPS1 and LHPS5 had antioxidant activity and cellular immunomodulatory activity in vitro, and could be used as antioxidant supplements or immunomodulatory agents.

Key words: Lycopi Herba; polysaccharides; antioxidant activity; immunoregulatory activity